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usmle-12751

A 41-year-old man presents to a New Mexico emergency department with a 12 hour history of shortness of breath and a nonproductive cough. He says that last week he experienced fevers, chills, fatigue, and myalgias but assumed that he simply had a cold. The symptoms went away after 3 days and he felt fine for several days afterward until he started experiencing shortness of breath even at rest. He works as an exterminator and recently had a job in a rodent infested home. Physical exam reveals a thin, tachypneic man with diffuse rales bilaterally. The most likely cause of this patient's symptoms is associated with which of the following?

usmle-12752

A 58-year-old woman presents to her primary care doctor with her husband. The patient's husband reports that his wife has been acting "funny" ever since she was in a motor vehicle accident 2 months ago. She's been very rude to him, their children, and her friends, often saying inappropriate things. She is not interested in her previous hobbies and will not watch her favorite television shows or play cards. Which of the following regions is suspicious for injury?

usmle-12753

A 49-year-old woman presents to her primary care doctor in late December with malaise. She reports worsening fatigue, myalgias, headache, and malaise that started 1 day ago. She works as a lunch lady at an elementary school. Her past medical history is notable for a distal radius fracture after a fall 2 years ago, but she is otherwise healthy and takes no medications. She does not smoke or drink alcohol. She is married and has 3 adult children who are healthy. Her temperature is 102.9°F (39.4°C), blood pressure is 101/61 mmHg, pulse is 112/min, and respirations are 21/min. On exam, she appears lethargic and uncomfortable but is able to answer questions appropriately. Breath sounds are normal bilaterally. She is started on intravenous fluids and a pharmacologic agent for treatment. Which of the following is the most likely mechanism of action of the drug being used to treat this patient?

usmle-12754

A 12-year-old boy is brought to his pediatrician with a high fever. He was feeling fatigued yesterday and then developed a high fever overnight that was accompanied by chills and malaise. This morning he also started complaining of headaches and myalgias. He has otherwise been healthy and does not take any medications. He says that his friends came down with the same symptoms last week. He is given oseltamivir and given instructions to rest and stay hydrated. He is also told that this year the disease is particularly infectious and is currently causing a global pandemic. He asks the physician why the same virus can infect people who have already had the disease and is told about a particular property of this virus. Which of the following properties is required for the viral genetic change that permits global pandemics of this virus?

usmle-12755

A 51-year-old man presents to his primary care provider complaining of fatigue, weight loss, and intermittent fevers for the past 6 months. He has had sexual intercourse with multiple men and women over the past year and does not use barrier protection. His last screen for sexually transmitted diseases was 10 years ago and was normal. His past medical history is notable for well-controlled asthma. He was involved in a motorcycle accident 2 years ago and suffered multiple fractured bones in his upper and lower extremities, all of which have healed. He has a distant history of cocaine abuse. He drinks 5-6 glasses of wine per week. His temperature is 100.8°F (38.2°C), blood pressure is 130/75 mmHg, pulse is 85/min, and respirations are 20/min. On examination, he appears cachectic but is pleasant and appropriately interactive. An HIV differentiation assay and follow-up Western blot are performed and are positive. The patient is started on tenofovir, abacavir, and efavirenz. However, the patient develops a hypersensitivity reaction to abacavir, so the decision is made to replace this medication with ritonavir. Which of the following adverse effects is this patient at greatest risk for as a result of this change in medication regimen?

usmle-12756

A 52-year-old male presents with recent weight loss, fever, and joint pain. He reports frequent bouts of diarrhea. An intestinal biopsy demonstrates PAS-positive, non-acid fast macrophage inclusions in the lamina propria. Which of the following organisms is likely responsible for this patient’s illness:

usmle-12757

A 26-year-old woman presents to a physician for genetic counseling, because she is worried about trying to have a child. Specifically, she had 2 siblings that died young from a lysosomal storage disorder and is afraid that her own children will have the same disorder. Her background is Ashkenazi Jewish, but she says that her husband's background is mixed European heritage. Her physician says that since her partner is not of Jewish background, their chance of having a child with Niemann-Pick disease is dramatically decreased. Which of the following genetic principles best explains why there is an increased prevalence of this disease in some populations?

usmle-12758

A 40-year-old man presents to his physician with complaints of a cough and fatigue that have significantly affected his daily routine. He lives alone and denies any sick contacts at his workplace but notes that he was formerly incarcerated and released 3 months ago. Upon further questioning, he states that he has coughed up blood a few times in the past weeks and has been having occasional night sweats. His chest radiograph is shown in Figure A. He is prescribed a treatment regimen that includes a drug that blocks the synthesis of mycolic acids. Which of the following is a potential side effect of this drug?

usmle-12759

A 24-year-old woman presents to her primary care doctor with a lesion on her labia. She first noticed the lesion 2 days ago. It is not painful. She denies vaginal discharge or dysuria. She has no past medical history and takes no medications. She has had 4 sexual partners in the past 8 months and uses the pull-out method as contraception. She drinks 12-16 alcoholic beverages per week and is a law student. Her temperature is 97.8°F (36.6°C), blood pressure is 121/81 mmHg, pulse is 70/min, and respirations are 16/min. On exam, she has an indurated non-tender ulcer on the left labia majora. There is no appreciable inguinal lymphadenopathy. Multiple tests are ordered and pending. This patient's condition is most likely caused by a pathogen with which of the following characteristics on histologic imaging?

usmle-12760

A 65-year-old Asian male presents to the emergency department complaining of shortness of breath. He reports a three-month history of progressively worsening shortness of breath and cough. One week ago, he started noticing blood in his handkerchief whenever he coughed. The patient immigrated from China ten years ago and has a history of tuberculosis as an adolescent. His medical history is also notable for alcohol abuse and alcoholic liver disease. He worked for many years as a dockworker in China. His temperature is 101.5°F (38.7°C), blood pressure is 130/70 mmHg, pulse is 115/min, and respirations are 20/min. Physical examination reveals rales in the right middle lung field. A chest CT of the patient is shown in Figure A. A biopsy of this lesion would likely reveal which of the following?

usmle-12761

A 61-year-old woman presents to her primary care doctor with her son who reports that his mother is not acting like herself. She has gotten lost while driving several times in the past 2 months and appears to be talking to herself frequently. Of note, the patient’s husband died from a stroke 4 months ago. The patient reports feeling sad and guilty for causing so much trouble for her son. Her appetite has decreased since her husband died. On examination, she is oriented to person, place, and time. She is inattentive, and her speech is disorganized. She shakes her hand throughout the exam without realizing it. Her gait is slow and appears unstable. This patient’s condition would most likely benefit from which of the following medications?

usmle-12762

A 36-year-old man presents to his primary care physician because of shortness of breath. He is an office worker who has a mostly sedentary lifestyle; however, he has noticed that recently he feels tired and short of breath when going on long walks with his wife. He also has had a hacking cough that seems to linger, though he attributes this to an upper respiratory tract infection he had 2 months ago. He has diabetes that is well-controlled on metformin and has smoked 1 pack per day for 20 years. Physical exam reveals a large chested man with wheezing bilaterally and mild swelling in his legs and abdomen. The cause of this patient's abdominal and lower extremity swelling is most likely due to which of the following processes?

usmle-12763

A 34-year-old male with a history of alcohol use is brought to the emergency department by ambulance after being found down on a Saturday night. He is difficult to arouse and has slurred speech when awake. He is febrile to 102°F (38.9 °C) and complains of right upper quadrant pain. Physical exam reveals shifting dullness in the abdomen and a palpable, tender liver edge. Lab tests show: Aspartate aminotransferase (AST): 247 U/L Alanine aminotransferase (ALT): 112 U/L Alkaline phosphatase (ALP): 70 U/L Hepatitis B surface antigen (HBsAg): Negative Hepatitis C antibody: Negative A liver biopsy is obtained and the results are displayed in Figure A. This patient’s most likely diagnosis primarily affects the same hepatic zone as which of the following disorders?

usmle-12764

A 72-year-old woman presents to the emergency room with dark stools. She first noticed that her stool appeared dark and tarry the day prior to presentation. She had 3 similar bowel movements over the past 24 hours. Her bowels movements are normally brown, solid, and occur once per day. Her past medical history is notable for gastroesophageal reflux disease, hypertension, hyperlipidemia, diabetes, and stage 3 chronic kidney disease. She takes omeprazole, enalapril, atorvastatin, and insulin. She does not smoke, and she drinks 6-8 glasses of wine per week. Her family history is notable for Bernard-Soulier disease in her paternal uncle and rectal cancer in her father. Her temperature is 98.6°F (37°C), blood pressure is 108/61 mmHg, pulse is 105/min, and respirations are 21/min. A fecal occult blood test is positive. Chest auscultation reveals normal breath sounds bilaterally and a harsh 3/6 crescendo-decrescendo murmur best heard at the upper right sternal border. Laboratory analysis is shown below: Hemoglobin: 10.4 g/dL Hematocrit: 30% Leukocyte count: 7,000/mm^3 with normal differential Platelet count: 240,000/mm^3 A notable finding on colonoscopy is shown in Figure A. Which of the following is the underlying cause of this patient's symptoms?

usmle-12765

A 25-year-old male presents to the general practitioner with a blood pressure of 150/100 mmHg that has remained elevated secondary to pharmacologic treatment. The physician orders a renal artery ultrasound which is given in Figure A. Which of the following mathematical equations explains the color findings on this ultrasound?

usmle-12766

A 39-year-old man presents to his primary care physician because he has been having severe headaches and fever for the last 2 days. He also says his right eyelid has been painlessly swelling and is starting to block his vision from that eye. He recently returned from a tour of the world where he visited Thailand, Ethiopia, and Brazil. Otherwise his past medical history is unremarkable. On presentation, his temperature is 102°F (38.8°C), blood pressure is 126/81 mmHg, pulse is 125/min, and respirations are 13/min. Physical exam reveals a nontender swelling of the right eyelid, lymphadenopathy, and an indurated red patch with surrounding erythema and local swelling on his left leg. Which of the following drugs should be used to treat this patient's condition?

usmle-12767

A 14-year-old male who is a recent immigrant from India visits your office complaining of difficulty walking. Physical examination reveals weakness upon right leg extension and absent right patellar tendon reflex. PCR of a stool sample and a swab of the pharynx both yield viral RNA. Which of the following best describes the likely causal virus of this patient’s symptoms?

usmle-12768

A 72-year-old woman presents to her primary care physician because she is coughing pink sputum and has difficulty breathing. She says that she was feeling pretty good until she traveled to her grandson's wedding last week. Since then she has had increasing difficulty sleeping and walking due to her shortness of breath. Physical exam reveals swollen ankles, basilar crackles bilaterally, and a murmur best heard in the left lateral decubitus position. She is already taking several medications for this condition; however, given the recent worsening of symptoms she is started on an additional medication. Which of the following is the most likely mechanism of action for the medication that was started in this patient?

usmle-12769

A 2-year-old boy is brought in to his pediatrician for a routine checkup. The parents mention that the child has been developing appropriately, although they have been noticing that the child appears to have chronic constipation. The parents report that their child does not routinely have daily bowel movements, and they have noticed that his abdomen has become more distended recently. In the past, they report that the patient was also delayed in passing meconium, but this was not further worked up. On exam, his temperature is 98.6°F (37.0°C), blood pressure is 110/68 mmHg, pulse is 74/min, and respirations are 14/min. The patient is noted to have a slightly distended abdomen that is nontender. Eventually, this patient undergoes a biopsy. Which of the following layers most likely reveals the causative pathologic finding of this disease?

usmle-12770

A 38-year-old female presents to the emergency room complaining of jaw pain and an inability to swallow. She reports that she is unable to fully open her mouth. She recently went on a multi-day hike in the mountains where she stepped on a nail sticking out of a piece of rotting wood. She also had several insect bites on the hike. She received all of her childhood vaccinations but has not received any vaccinations since she was in college. Her temperature is 99°F (37.2°C), blood pressure is 115/75 mmHg, pulse is 100/min, and respirations are 18/min. On examination, she has limited range of motion in her jaw. She has a 1 cm x 1 cm erythematous puncture wound on the sole of her right foot. A Gram stain of a wound culture is shown in Figure A. Immunohistochemical staining is positive for dipicolinic acid. Which of the following diseases is caused by an organism that produces a similar structure to the one seen on staining?

usmle-12771

A 14-year-old male of eastern European descent presents to the free clinic at a university hospital for a respiratory infection, which his mother explains occurs quite frequently. The male is noted to be of short stature, have a gargoyle-like facies, clouded corneas, poor dentition, and is severely mentally retarded. A urinalysis revealed large amounts of heparan and dermatan sulfate. Which of the following is the most likely diagnosis?

usmle-12772

A 24-year-old male presents to the emergency room with a cough and shortness of breath for the past 3 weeks. You diagnose Pneumocystis jiroveci pneumonia (PCP). An assay of the patient's serum reveals the presence of viral protein p24. Which of the following viral genes codes for this protein?

usmle-12773

A 42-year-old woman comes to the clinic complaining of upper abdominal pain. Her symptoms started 1 month ago with vague abdominal discomfort following a meal at a steakhouse. Since then the pain has progressed to the point that she has more than 5 episodes a week. The pain is worse with eating but has not affected her appetite. She also reports a burning sensation in her chest when she lies down at night after dinner. She denies weight loss or dysphagia. She takes no medications except daily calcium supplements. She drinks 2 glasses of wine per week and denies tobacco use. Her blood pressure is 110/78, pulse is 72/min, and respirations are 13/min. On physical examination, the patient’s abdomen is soft and non-distended. Normal bowel sounds are appreciation. There is mild epigastric tenderness but no guarding and no rebound. Fecal occult blood is negative. Which of the following is the next best step in management?

usmle-12774

You are seeing an otherwise healthy 66-year-old male in clinic who is complaining of localized back pain and a new rash. On physical exam, his vital signs are within normal limits. You note a vesicular rash restricted to the upper left side of his back. In order to confirm your suspected diagnosis, you perform a diagnostic test. What would you expect to find on the diagnostic test that was performed?

usmle-12775

A 51-year-old gentleman presents with new onset bilateral paresthesias of his feet. He also admits that he has not been able to exercise as much as previously and his friends have commented that he looks pale. Upon physical exam you find that he has conjunctival pallor and mildly decreased sensation and proprioception on his feet bilaterally. Based on your suspicions you decide to obtain a blood smear where you see megaloblasts as well as hypersegmented neutrophils. Given these findings you decide to investigate the cause of his disorder by injecting an intramuscular vitamin, then feeding him a radiolabeled version of the same vitamin orally. After waiting 24 hours you see that no radiolabeled vitamin appears in the urine so you repeat the test with intrinsic factor added to the oral mixture, at which point 20% of the radiolabeled vitamin appears in the urine. Which of the following is the most likely etiology of this gentleman's symptoms?

usmle-12776

A 76-year-old man is brought to his physician's office by his wife due to progressively worsening hearing loss. The patient reports that he noticed a decrease in his hearing approximately 10 years ago. His wife says that he watches television at an elevated volume and appears to have trouble understanding what is being said to him, especially when there is background noise. He states that he also experiences constant ear ringing and episodes of unsteadiness. On physical examination, the outer ears are normal and otoscopic findings are unremarkable. The patient is unable to repeat the sentence said to him on whisper testing. When a vibrating tuning fork is placed in the middle of the patient's forehead, it is heard equally on both ears. When the vibrating tuning fork is placed by the ear and then on the mastoid process, air conduction is greater than bone conduction. Which of the following structures is most likely impaired in this patient?

usmle-12777

A 13-year-old girl is brought to the clinic by her parents for joint pain for the past 4 days. She reports a 6/10, intermittent, dull pain in her knees and ankles. The pain does not stay in one place and over the past day, her right knee has become red and swollen. She endorses subjective fever and fatigue but denies chest pain, dizziness, abdominal pain, gastrointestinal signs, or urinary changes. Her past medical history is unremarkable except for an episode of sore throat 3 weeks ago. A physical examination demonstrates an erythematous, swollen right knee that is tender upon palpation and skin findings on the upper left arm shown in Figure A. What finding would you expect in this patient?

usmle-12778

A 27-year-old medical student travels to Haiti to complete a research project in a local hospital. Upon her return, she reports feeling perfectly healthy but is found to have a type IV hypersensitivity reaction to a particular purified protein derivative as seen in Figure A. Her primary care physician prescribes her one drug. Which of the following is a characteristic of the drug she is most likely prescribed?

usmle-12779

A seven-year old recent immigrant from Haiti presents to a primary care clinic to establish care. Per his mother, the child has no known health concerns and an unremarkable birth history. He and two of his siblings have several crusted, pyodermic, weeping skin lesions, mainly on the face and the arms, as seen in Figure A. Today his temperature is 97°F (36°C), blood pressure is 100/60 mmHg, pulse is 95/min, and respirations are 17/min. Of the following descriptions, which is most likely to describe an organism that could result in this patient's presentation?

usmle-12780

A 35-year-old female presents to her primary care physician with dull left flank pain that has increased in intensity over the last several weeks. She denies any associated symptoms, including nausea/vomiting, dizziness, fevers, or dysuria. Her vital signs are stable and within normal limits. Physical examination reveals an abnormal mass on palpation of the left flank. A CT scan of the abdomen is obtained and shown in Figure A (The arrows were placed by the radiologist to note the findings of interest). To confirm the diagnosis, percutaneous renal biopsy is carried out and shows renal angiomyolipoma. Which of the following diseases is most commonly associated with this patient's findings?

usmle-12781

A 1-year-old girl is brought to her pediatrician because she has not been feeding for the last 2 days. Specifically, her parents are worried that she appears listless and doesn't respond to stimuli as she did previously. She appeared to be healthy at birth though she has been missing developmental milestones since then. For example, she cannot sit unaided and does not repeat sounds or actions. Physical exam reveals hepatosplenomegaly and cherry red spots on her macula. Examination of a peripheral blood smear reveals cells that appear as in Figure A. Which of the following enzymes is most likely defective in this patient?

usmle-12782

An 81-year-old woman presents to your office accompanied by her husband. She has been doing well except for occasional word finding difficulty. Her husband is concerned that her memory is worsening over the past year. Recently, she got lost twice on her way home from her daughter’s house, was unable to remember her neighbor’s name, and could not pay the bills like she usually did. She has a history of hypertension and arthritis. She has no significant family history. Her medications include a daily multivitamin, hydrochlorothiazide, and ibuprofen as needed. Physical exam is unremarkable. Which of the following is associated with an increased risk of this patient’s disease?

usmle-12783

A 45-year-old executive travels frequently around the world. He often has difficulty falling asleep at night when he returns home. You suspect a circadian rhythm disorder is responsible for his pathology. Which of the following regulates the circadian rhythm?

usmle-12784

A 9-year-old boy is getting fitted for leg braces because he has become too weak to walk without them. He developed normally until age 3 but then he began to get tired more easily and fell a lot. Over time he started having trouble walking and would stand up by using the Gower maneuver. Despite this weakness, his neurologic development is normal for his age. On exam his calves appeared enlarged and he was sent for genetic testing. Sequence data showed that he had a mutation leading to a string of incorrect amino acids. Which of the following types of mutations is most likely the cause of this patient's disorder?

usmle-12785

A 5-year-old boy is brought to an urgent care clinic by his mother. The boy has had a fever and flu-like symptoms for 7 days. Last evening, he developed a rash as shown in Figure A. This morning, his mother noted the findings shown in Figure B, which prompted her to bring him for evaluation. All of his vaccinations are up to date. Which of the following is the most likely cause of his presentation?

usmle-12786

A 36-year-old male is brought to the emergency department for severe chest pain and vomiting. He reports sudden onset 10/10 pain concentrated along his lower chest/epigastric region that radiates to his back for the past 3 hours. He denies any precipitating event, alcohol use, exertion, biliary colic, or family history of coronary artery disease. Medical history is significant for hypertension for which he recently started taking a “water pill.” Electrocardiogram (ECG) demonstrates normal sinus rhythm, and troponins are negative. Additional laboratory findings are shown below: Serum: Na+: 138 mEq/L K+: 3.9 mEq/L Cl-: 101 mEq/L Ca2+: 8.5 mg/dL Total cholesterol: 210 mg/dL (Normal: < 200 mg/dL) Triglycerides: 1,528 mg/dL (Normal: < 150 mg/dL) CRP: 28 mg/dL (Normal: < 3 mg/dL) Amylase: 582 U/L (Normal: 23-85 U/L) Lipase: 1,415 U/L (Normal: 0-160 U/L) What is the best medication for this patient in the long-term following initial stabilization?

usmle-12787

A 3-year-old girl is brought by her mother to her pediatrician. Her mother reports that the child has had frequent headaches over the past month. She has also vomited every day over the past 2 weeks and has been increasingly fatigued to the point that she has been unable to attend preschool. The child was born at 39 weeks gestation and was previously healthy. She was previously able to walk up and down stairs with alternating feet, ride a tricycle, dress herself, and use 3 word sentences in speech. On examination, the child is lethargic and complaining of a holocranial headache. Her pupils are equally round and reactive to light. Cranial nerves II-XII are intact. Strength is 5/5 in the bilateral upper and lower extremities. Results of a brain MRI are shown in Figure A. Which of the following will most likely be seen on biopsy of the lesion?

usmle-12788

A 43-year-old woman is found in the hospital to have a plasma sodium concentration of 126 mg/dL. She was hospitalized after she expressed suicidal ideations and was started on a medication for major depressive disorder. Her past medical history is significant for diabetes for which she is currently taking metformin. Her blood pressure while in the hospital has been around 130/85 mmHg and she is not taking any other medications. Urinalysis shows a serum osmolality of 1085 mOsm/L. Which of the following best describes the cell bodies of the cells that are behaving abnormally in this patient?

usmle-12789

A previously healthy 28-year-old man presents to the physician complaining of recent unintentional weight loss, flatulence, and foul-smelling stools. He reports having severe abdominal cramping that is worse in his right upper abdomen as well as intermittent bloody stools. He has experienced these symptoms since his return from a backpacking trip in Australia, one month ago. He is prescribed a medication and advised to refrain from alcohol consumption to avoid adverse effects of the drug. Which of the following findings on pathology would most likely correspond to the patient’s diagnosis?

usmle-12790

A 73-year-old man presents to your office accompanied by his wife. He has been experiencing a tremor in his right hand for the last several months that seems to be worsening. He does not have any other complaints and says he’s “fine.” His wife thinks that he has also had more difficulty walking. His history is significant for hypertension and an ischemic stroke of the right middle cerebral artery 2 years ago. His medications include hydrochlorothiazide and daily aspirin. On physical exam you note that the patient speaks with a soft voice and has decreased facial expressions. He has a resting tremor that is worse on the right side. He has increased resistance to passive movement when you flex and extend his relaxed wrist. He has 5/5 strength bilaterally. Neuronal degeneration in which of the following locations is most likely responsible for the progression of this disease?

usmle-12791

A 45-year-old male who recently returned from a business trip abroad presents to the emergency room complaining of several days of diarrhea. He has up to 10 voluminous watery stools per day accompanied by mild nausea and abdominal cramps. In addition, he recently noticed blood on his toilet paper after wiping but not in the toilet. His past medical history is notable for gout, peptic ulcer disease, and gastroesophageal reflux disease. He takes allopurinol and omeprazole. His temperature is 100.6°F (38.1°C), blood pressure is 120/75 mmHg, pulse is 105/min, and respirations are 18/min. On examination, he has dry mucous membranes and delayed capillary refill. He demonstrates mild tenderness to palpation in all quadrants of his abdomen. Figure A shows the gram stain for the organism that is isolated from stool culture. These organisms were also found to ferment lactose quickly. The mechanism that is most likely responsible for this patient's diarrhea is similar to that used by an organism with which of the following characteristics?

usmle-12792

A 7-year-old boy is brought to the hospital for evaluation, he is accompanied by agents from child protective services after he was rescued from a home where he was being neglected. He was found locked in a closet and says that he was fed only once every 2 days for the past month. On presentation, he is found to be extremely emaciated with protruding ribs and prominent joints. He is provided with an appropriate rehydration and nourishment therapy. Despite his prolonged nutritional deprivation, the patient demonstrates appropriate cognitive function for his age. The transporter responsible for preventing cognitive decline in this malnourished patient has which of the following characteristics?

usmle-12793

A 61-year-old female presents to the emergency room for a headache and vision loss. She reports a 3-hour history of acute-onset dull headache. She also says she cannot see out of part of her eye. Her past medical history is notable for hypertension, hyperlipidemia, and a prior myocardial infarction. She takes enalapril, atorvastatin, aspirin, and metoprolol. On exam, she is alert and oriented to person, place, and time. She has 5/5 strength and full sensation to light touch in her bilateral upper and lower extremities. Her brachioradialis, triceps, patellar, and Achilles reflexes are symmetric and 2+ bilaterally. Fundoscopic examination reveals a normal retina. Visual field examination demonstrates an inability to see in the superior right visual field. This patient’s condition is likely due to a lesion in which of the following locations?

usmle-12794

A 10-year-old boy is brought to the emergency department following a seizure episode. His father reports that he was practicing piano when his whole body started to jerk uncontrollably. He did not respond to verbal stimuli during the episode, which lasted about 30 seconds. The patient denies any memory of the event. His father denies trauma to the head, bleeding, loss of continence, recent fever, or infections. The patient reports that since 4 months ago, he has been experiencing intermittent, sudden jerks of his right foot that he cannot control. Subsequent workup via a muscle biopsy is shown in Figure A. From which family member did this patient most likely inherit the disease?

usmle-12795

A 36-year-old woman with a past medical history of diabetes comes to the emergency department for abdominal pain. She reports that a long time ago her gynecologist told her that she had “some cysts in her ovaries but not to worry about it.” The pain started last night and has progressively gotten worse. Nothing seems to make it better or worse. She denies headache, dizziness, chest pain, dyspnea, diarrhea, or constipation; she endorses nausea, dysuria for the past 3 days, and chills. Her temperature is 100.7°F (38.2°C), blood pressure is 132/94 mmHg, pulse is 104/min, and respirations are 14/min. Physical examination is significant for right lower quadrant and flank pain with voluntary guarding. What is the most likely pathophysiology of this patient’s condition?

usmle-12796

A 6-year-old Russian boy who recently immigrated to the United States presents to your office with fever and dyspnea. On examination of the oropharynx, you note a grayish-white pseudomembrane and uneven elevation of the soft palate. The patient displays marked enlargement of the cervical lymph nodes. Which of the following describes the organism responsible for this patient's disease?

usmle-12797

A 65-year-old Caucasian gentleman presents to the clinic with an ulcerated lesion on his nose that has been present for four months. He recalls picking at the lesion when it first developed and reports that it never completely healed since then. The patient is a retired school bus driver and now spends most of his time gardening at home. He has no known family history of skin cancer. On exam, the patient has stable vital signs and is afebrile. Physical exam findings are shown in Figure A. Which of the following would be seen on histological studies of a biopsy specimen?

usmle-12798

A 32-year-old male presents to the emergency department because of fever and diarrhea. He was in his normal state of health until 2 weeks ago when he went abroad on a vacation. During his trip he went kayaking, visited spas, interacted with local animals, and ate local foods. Since returning he has had 3-day history of fever, cough, headache, and diarrhea. He drinks socially and has a 15-pack-year history of smoking. On presentation his temperature is 102.3°F (39.1°C), blood pressure is 105/62 mmHg, pulse is 91/min, respirations are 18/min, and O2 saturation is 91% on room air. Chest exam reveals fine crackles on auscultation. Chest radiograph reveals patchy infiltrates in both lungs and labs reveal mild hyponatremia and mild elevation of AST/ALT levels. The organism that is most likely responsible for this patient's symptoms is associated with which of the following characteristics?

usmle-12799

A 82-year-old woman is brought to the emergency department from a retirement community after she was found down during the evening. On presentation, she complains that she experienced several hours of nausea, vomiting, crampy abdominal pain, and diarrhea prior to blacking out. She said that she cannot recall any factors that may have triggered her symptoms; however, she recalls that some of her friends with whom she eats also had similar symptoms earlier in the day and were brought to the hospital. They often go for walks and occasionally cook for themselves from a garden that they keep in the woods behind the facility. One of the residents on the team recalls seeing other patients from this facility earlier today, one of whom presented with kidney failure and scleral icterus prior to passing away. The enzyme most likely affected in this case has which of the following functions?

usmle-12800

A 55-year-old Caucasian male with a history of hypertension who had just emigrated from Scotland to the United States comes in to your office to establish care. He has not seen a medical provider in almost fifteen years. His father had cirrhosis and died of liver cancer at age 61 while his mother is still alive and healthy. He does not smoke tobacco and has one alcoholic beverage per week. He takes multivitamins and herbal supplements for sleep. His review of systems is positive for fatigue and weakness, joint pain in his hands, decreased libido and states that he tans easily. His vital signs are within normal limits and his physical exam is notable for obesity, MCP joint swelling and tenderness bilaterally. He also has generalized skin hyperpigmentation (Figure A). His laboratory results are notable for a hemoglobin A1c of 7.9%, AST 156 U/L and ALT 190 U/L. What is the most likely underlying mechanism for this patient’s presenting symptoms?

usmle-12801

A 56-year-old immigrant from Haiti arrives in the hospital with a three week history of cough and fever. He has a history of hypertension, hyperlipidemia, and has a 30 pack year smoking history. On physical exam, the upper right lung field is dull to percussion. There are no other significant exam findings. Her temperature is 98.7 °F (37 °C), blood pressure is 142/85 mmHg, pulse is 87/min, respirations are 18/min. A chest radiograph is obtained and the result is shown in Figure A. A sputum sample appears as in Figure B. The most likely causative organism in this case can be specifically visualized due to which of the following characteristic properties?

usmle-12802

A 30-year-old man is brought to the doctor's office by his wife. She complains that over the past week there have been 3 episodes where he has fallen asleep while speaking with her. She mentioned that these events began a few months ago and have been increasing in frequency. She also says that his snoring has gotten to the point where she has a hard time sleeping next to him. When asked, the patient says that he frequently falls asleep while reading or watching television in the afternoons and feels refreshed after a short nap. The patient is worried because he sometimes hears people who aren’t in the room as he falls asleep. He is worried he might be “going crazy.” He has noticed that when his friends tell him a joke or he laughs at something on the TV, he drops whatever he’s holding and feels like his legs become weak. These episodes self-resolve in a few seconds. Examination shows a morbidly obese man in no acute distress. Which of the following is the best treatment for the most likely cause for this patient’s illness?

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A 24-year-old man visits his primary care doctor complaining of increasing shortness of breath, lightheadedness, and weight gain. He has no medical problems. He works as a landscaper but has recently been unable to keep up with his duties due to fatigue. He recalls having a large rash on his arm 6 weeks ago but did not seek medical care at that time (Figure A). On physical exam, temperature is 37.1 deg C (98.8 deg F), pulse 40/min and weak, blood pressure is 110/68 mmHg, and respiratory rate is 20/min. He is pale and there is swelling of the lower extremities is noted. A 12-lead EKG is shown (Figure B). What is the most likely cause of the patient’s symptoms?

usmle-12804

A 26-year-old man with no past medical history is brought in to the trauma bay by ambulance after sustaining a motorcycle crash against a parked car. The patient is alert and oriented with no focal neurologic defects. The patient has a few lower extremity abrasions but is otherwise healthy and is discharged. One week later, the patient returns to the emergency department with a 2-day history of high fevers and redness on his left lower leg. On exam, his temperature is 102.0°F (38.9°C), blood pressure is 70/44 mmHg, pulse is 108/min, and respirations are 14/min. The patient appears toxic, and his left lower leg is tense, erythematous, and tender to palpation between the ankle and the knee. The exam is notable for tense bullae developing on the lateral calf. Palpation near the bullae is notable for crepitus. Which of the following toxins is likely responsible for this finding?

usmle-12805

A 3-year-old boy is brought to his pediatrician for evaluation because his parents have been concerned by a number of troubling signs. Specifically, they have noticed that he has been exhibiting aggressive behavior as well as hyperactivity. In addition, he has had intellectual disability and is slow to hit developmental milestones. Physical exam reveals coarse facies, short stature, and joint stiffness. Eye exam reveals no abnormalities of the cornea or lens. Based on these findings, the patient is referred to a geneticist for further evaluation. Which of the following substances would most likely accumulate in the cells of this patient?

usmle-12806

A 66-year-old man presents to the office complaining of abdominal pain. He reports that the pain is mid-epigastric and “gnawing.” It worsens after meals but improves “somewhat” with antacids. The patient’s medical history is significant for hypertension, hyperlipidemia, and gout. He takes aspirin, lisinopril, atorvastatin, and allopurinol. He uses ibuprofen during acute gout attacks and takes over the counter multivitamins. He also started drinking ginkgo tea once a week after his wife saw a news story on its potential benefits. The patient has a glass of whiskey after work 2 nights a week but denies tobacco or illicit drug use. An upper endoscopy is performed that reveals a gastric ulcer. A urease breath test is positive for Heliobacter pylori. The patient is prescribed bismuth subsalicylate, omeprazole, metronidazole, and tetracycline for 2 weeks. At follow-up, the patient continues to complain of abdominal pain. He has taken all his medications as prescribed along with 10-12 tablets of antacids a day. He denies hematemesis, hematochezia, or melena. Biopsy from the previous upper endoscopy was negative for malignancy. A repeat urease breath test is positive. Which of the following is the most likely cause for the patient’s poor treatment response?

usmle-12807

A 52-year-old man presents to his primary care physician for his annual check-up. He says that he has no health concerns; however, his wife is concerned that he has become increasingly forgetful. For example, he has become forgetful during his daily activities and recently has been getting lost during errands like shopping. She says that these symptoms have been occurring for about a year. She says that she became alarmed when he started forgetting the names of their children. Finally, over the last month he has become more irritable, which has led to several confrontations at work. Based on the age of onset for his disease, the patient is referred for genetic testing. Which of the following chromosomes contain genes that may be mutated in this patient's disease?

usmle-12808

A 14-year-old boy presents to his pediatrician with a 5-day history of abdominal pain and bloody stool. He denies having a fever and says that he has not experienced any other symptoms associated with the abdominal pain. He has no past medical history and does not take any medications or supplements. His family history is significant for a grandfather who developed Alzheimer disease at age 80 and a cousin who died at age 21 from colon cancer. Physical exam is unremarkable. Based on clinical suspicion a colonoscopy is obtained showing hundreds of small polyps in the colon. A mutation of a gene on which of the following chromosomes is most likely responsible for this patient's symptoms?

usmle-12809

A 45-year-old man with a history of poorly controlled human immunodeficiency virus (HIV) infection presents to the emergency room complaining of clumsiness and weakness. He reports a 3-month history of worsening balance, asymmetric muscle weakness, and speech difficulties. He recently returned from a trip to Guatemala to visit his family. He has been poorly compliant with his anti-retroviral therapy and his most recent CD4 count was 195. His history is also notable for rheumatoid arthritis and hepatitis C. His temperature is 99°F (37.2°C), blood pressure is 140/90 mmHg, pulse is 95/min, and respirations are 18/min. On exam, he has 4/5 strength in his right upper extremity, 5/5 strength in his left upper extremity, 5/5 strength in his right lower extremity, and 3/5 strength in his left lower extremity. His speech is disjointed with intermittent long pauses between words. Vision is 20/100 in the left eye and 20/40 in his right eye; previously, his eyesight was 20/30 bilaterally. This patient most likely has a condition caused by which of the following types of pathogens?

usmle-12810

A 58-year-old male undergoes a surveillance colonoscopy in which a 2 cm adenoma is identified and removed. Had this adenoma not been excised, the patient would have been at risk of progression to carcinoma. Which of the following is the final mutational step in the progression from adenoma to carcinoma?

usmle-12811

A 24-year-old college student presents to student health with 2 days of developing a sore throat, runny nose, and a cough that started today. He states that he has been getting mild fevers which began yesterday. On exam, his temperature is 102.0°F (38.9°C), blood pressure is 135/76 mmHg, pulse is 95/min, and respirations are 12/min. His physician recommends over-the-counter cold medications and reassures him that his symptoms are due to a viral infection that is self-limited. Which of the following best describes the most likely cause of his illness?

usmle-12812

A 45-year-old man is brought to the emergency department after being found down outside of a bar. He does not have any identifying information and is difficult to arouse. On presentation, his temperature is 101.2°F (38.4°C), blood pressure is 109/72 mmHg, pulse is 102/min, and respirations are 18/min. Physical exam reveals an ill-appearing and disheveled man with labored breathing and coughing productive of viscous red sputum. Lung auscultation demonstrates consolidation of the left upper lobe of the patient. Given these findings, cultures are obtained and broad spectrum antibiotics are administered. Which of the following agar types should be used to culture the most likely organism in this case?

usmle-12813

A 5-year-old boy presents to a pediatric orthopedic surgeon for evaluation of spinal curvature. His primary care physician noticed during an annual checkup that the boy's shoulders were uneven, and radiograph revealed early onset scoliosis. His past medical history is significant for multiple fractures as well as short stature. Based on the early presentation of scoliosis and the unusual history of fractures, the surgeon orders further workup and discovers a genetic mutation in an extracellular protein. This protein exists in two different forms. The first is an insoluble dimer that is linked by disulfide bonds and links integrins to the extracellular matrix. The second is a soluble protein that assists with clotting. Based on these descriptions, which of the following proteins is most likely mutated in this patient?

usmle-12814

A 78-year-old right-handed male is brought in by ambulance after being found down in his home. After being aroused, the patient has difficulty answering questions and appears to be frustrated by his inability to communicate. He is able to speak his name and a few other words but his speech is not fluent. Subsequent neurologic exam finds that the patient is able to comprehend both one and two step instructions; however, he is unable to repeat phrases despite being able to understand them. He also has difficulty writing despite retaining fine motor control. CT reveals an acute stroke to his left hemisphere. Damage to which of the following sets of structures would be most likely to result in this pattern of deficits?

usmle-12815

A 24-year-old man presents to your clinic complaining of a cough that started 3 weeks ago. Over the past two weeks he has had less energy and has developed fevers and chills. Vital signs are as follows: T 102.6 F HR 78 bpm, BP 124/76 mmHg, RR 10 bpm. Chest radiography is seen in Figure A. Sputum sample is obtained and the results are shown in Figure B. What is a common risk factor for this patient's condition?

usmle-12816

A 53-year-old man is brought by his daughter to the clinic. She lives a town away but visits often. She reports that on recent visits, his mood has been volatile, ranging from aggressive at some moments to depressed at others. She has noticed some new jerky movements which she has never seen before and has been quite forgetful. She is concerned that he might be abusing alcohol and drugs. What changes would you expect in the brain of this patient?

usmle-12817

A 55-year-old man is brought to the emergency department for 1 episode of bloody emesis. He reports feeling lightheaded this morning and shortly after breakfast, he felt nauseous and had an episode of bloody emesis. He denies any trauma, fever, abnormal ingestions, or recent infections. He endorses black stools over the past few days. His past medical history is significant for alcohol abuse and cirrhosis. A physical examination demonstrates mild jaundice and ascites. What is the mechanism of action of the medication that can be used in the management of this patient’s condition?

usmle-12818

A 68-year-old asplenic male from Long Island presents with fever and shaking chills for the past two weeks. He attributes his symptoms to a tick bite that he incurred a day or two prior to the onset of symptoms. A blood test reveals normocytic, normochromic anemia with an increase in total bilirubin. A Giemsa-stained thin blood smear was performed (Figure A). Which of the following is the most likely cause of his symptoms and lab results?

usmle-12819

A 43-year-old gentleman with a history of intravenous drug use presents with general fatigue and weakness accompanied by swelling in his ankles and lower legs. Further questions elicit that he has had many infections due to his drug use but has not previously had any cardiac or pulmonary issues. Upon physical examination you notice a holosystolic blowing murmur radiating to the right sternal border, which the patient denies being told about previously. Based on this presentation, what is the most likely cause of the murmur?

usmle-12820

A 25-year-old man with no significant past medical history is brought in by ambulance after a witnessed seizure at home. On physical exam, temperature is 102.3 deg F (39.1 deg C), blood pressure is 90/62 mmHg, pulse is 118/min, and respirations are 25/min. He is unable to touch his chin to his chest and spontaneously flexes his hips with passive neck flexion. Appropriate empiric treatment is begun. CT head is unremarkable, and a lumbar puncture sample is obtained. Gram stain of the cerebrospinal fluid (CSF) reveals gram-positive diplococci. Which of the following would you expect to see on CSF studies?

usmle-12821

A 66-year old man with a 45-pack-year smoking history presents with abdominal pain and constipation. He reports that he has had a worsening cough for several months and has lost 20 pounds over this time period. You order a complete metabolic profile, which demonstrates hypercalcemia. A chest radiograph shows a centrally located mass suspicious for malignancy. Which of the following is the most likely explanation?

usmle-12822

A 21-year-old male presents to the ED with a stab wound to the right neck. The patient is alert and responsive, and vital signs are stable. Which of the following neurologic findings would most likely support the diagnosis of right-sided spinal cord hemisection?

usmle-12823

A 46-year-old man presents to a physician three days after arriving in Morocco. He endorses acute onset of painless, profuse watery diarrhea that appears white and cloudy. The patient denies bloody stool, vomiting, or subjective fevers. Vital signs are T 98.6, HR 120, RR 17, and BP 85/50. On physical exam, the patient has dry mouth, decreased skin turgor, and cold clammy skin. His peripheral pulse is rapid and thready. The toxin responsible for this clinical presentation has a mechanism of action that is most similar to which other toxin?

usmle-12824

A 47-year-old man presents as a new patient at an outpatient clinic. He has never seen a physician before, but was motivated by his 40-year-old brother's recent heart attack and seeks to optimize his health. In particular, he read that uncontrolled atherosclerosis can lead to a heart attack. Which molecule is downregulated in response to the advent of atherosclerosis?

usmle-12825

A 35-year-old female presents to the emergency room complaining of diarrhea and dehydration. She has been experiencing severe watery diarrhea for the past 3 days. She reports that she has been unable to leave the bathroom for more than a few minutes at a time. She noticed earlier today that there was some blood on her toilet paper after wiping. She recently returned from a volunteer trip to Yemen where she worked at an orphanage. Her past medical history is notable for psoriasis for which she takes sulfasalazine. The patient drinks socially and does not smoke. Her temperature is 99°F (37.2°C), blood pressure is 100/55 mmHg, pulse is 130/min, and respirations are 20/min. Mucus membranes are dry. Her eyes appear sunken. Capillary refill is 4 seconds. The patient is started on intravenous fluid resuscitation. Which of the following processes is capable of transmitting the genetic material for the toxin responsible for this patient’s condition?

usmle-12826

A 65-year-old man presents to the emergency department with a complaint of intense pain in his right foot for the past month, along with fever and chills. He denies any traumatic injury to his foot in recent memory. He has a medical history of poorly-controlled type II diabetes and is a former smoker with extensive peripheral vascular disease. On physical exam, the area of his right foot around the hallux is swollen, erythematous, tender to light palpation, and reveals exposed bone. Labs are notable for elevated C-reactive protein and erythrocyte sedimentation rate. The physician obtains a biopsy for culture. What is the most likely causative organism for this patient’s condition?

usmle-12827

A 4-year-old boy presents to the opthalmologist for a down- and inward dislocation of the lens in his left eye. On physical exam, the boy has a marfanoid habitus and mental retardation. Biochemical tests were performed to locate the exact defect in this boy. It was found that there was a significant reduction of the conversion of 5,10-methyltetrahydrofolate to 5-methyltetrahydrofolate. Which of the following is the diagnosis?

usmle-12828

A 55-year-old female is hospitalized following a burn on 60% of her body. She is being treated in the ICU, and her condition remains poor. On rounds one morning, her vitals are as follows: T 38.5 C, HR 100, BP 115/75 mmHg, RR 25. In addition, physical exam shows the findings in Figure A. Which of the following is the most likely diagnosis?

usmle-12829

A 17-year-old male presents to the pediatrician complaining of malaise. He reports a three-day history of fatigue, painful joints, a skin rash, and fevers. He was recently seen by his pediatrician for a sore throat of presumed viral etiology. His past medical history is notable for severe mononucleosis one year ago and poorly controlled asthma. He currently takes inhaled salmeterol and fluticasone. His temperature is 101.0°F (38.3°C), blood pressure is 120/70 mmHg, pulse is 110/min, and respirations are 20/min. Range of motion is full in the bilateral upper and lower extremities; however, the patient reports mild pain in his elbow and knees. A notable physical examination finding is shown in Figure A. Antibodies directed against a protein with which of the following functions are most likely responsible for this patient’s condition?

usmle-12830

A 78-year-old patient arrives at the emergency department after slipping on the ice while shoveling snow. He denies palpitations, diaphoresis, or chest pain. He did not lose consciousness or hit his head during the fall. His past medical history is notable for poorly controlled hypertension and an asymptomatic left bundle branch block. Vitals in the emergency department are temperature is 99.1°F (37.3°C), blood pressure is 168/86 mmHg, pulse is 85/min, respirations are 18/min, and oxygen saturation 99% on room air. Physical exam shows no peripheral edema and lungs clear to auscultation. An EKG is performed in the emergency department and is shown in Figure A. Echocardiogram shows no valvular abnormalities with an ejection fraction of 55%. Troponin-I for this patient is 0.01 ug/L. On cardiac exam, an extra heart sound is auscultated. During which phase of the cardiac cycle would this sound most likely appear based on this patient’s history and EKG?

usmle-12831

A 64-year-old man presents to the clinic complaining of a cough for the past 2 weeks. He reports that it has been getting worse to the point that sometimes it is difficult for him to breath. He denies any symptoms suggestive of an upper respiratory infection (e.g., runny nose, congestion, or headache), heartburn, palpations, weight loss, or rashes but reports “feeling warm” over the past couple of days. His family history is unremarkable. When asked about his past medical history, the patient claims that he “hasn’t seen a doctor since his thirties.” He denies smoking in the past but endorses drinking “1-2 bottles of something” every night. Physical examination demonstrates halitosis, mild scleral icterus, and skin findings shown in Figure A. No right upper quadrant pain or wheezing were detected. What is the most likely explanation for this patient’s symptoms?

usmle-12832

A 21-year-old woman presents to her primary care doctor for an initial visit. She is a Syrian refugee and arrived in the United States 2 weeks ago. She has been living in refugee camps throughout Jordan and Turkey for the past 2 years. She has a 3-year-old son and reports that she has limited her food intake in order to ensure that her son has adequate nutrition. She reports decreased vision most noticeable over the past 6 months that is worse in low-light settings. She also reports severe dry eyes that have not improved with eye drops. She has no known past medical history and takes no medications. Her body mass index is 18.1 kg/m^2. On exam, she appears lethargic but is able to respond to questions appropriately. She has dry mucous membranes and decreased skin turgor. Her conjunctiva appears dry, thickened, and wrinkled. There is a small corneal ulcer on the lateral aspect of the left eye. This patient's symptoms are most consistent with a deficiency in a vitamin that contributes to which of the following processes?

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A 12-year-old boy is brought by his mother to a neurologist for continuing evaluation of seizures. His seizures were previously well-controlled on medication but over the last month he has been having seizures several times per week. The boy is non-verbal and has had severe developmental delays and cognitive disability since birth. On exam, the boy is found to be enthusiastically playing with the toys in the office and laughing at almost any stimulus. Furthermore, his movements are found to be uncoordinated with a wide based gait. Previous genetic testing has revealed an abnormality in an E3 ubiquitin ligase gene. Compared to unaffected individuals, which of the following patterns of gene expression is most likely seen in this patient?

usmle-12834

A 71-year-old woman presents to the emergency department with a headache for the past 30 minutes. She says that this is the worst headache of her life and that it came on suddenly after she hit her head. She says that she has also been experiencing visual problems with double vision when she looks to the left or the right. Visual examination reveals that her right eye cannot move right past the midline and her left eye cannot move left past the midline. Which of the following is most likely responsible for this patient's visual defects?

usmle-12835

A 23-year-old man comes to the emergency department complaining of 10/10 abdominal pain. He describes the pain as sharp, stabbing, intermittent, and concentrated at the left lower quadrant. It started about 3 hours ago with no obvious precipitating factor. He reports multiple similar episodes in the past but they have all resolved within 1 hour or so. He denies fever, weight changes, headaches, nausea/vomiting, or gastrointestinal changes but endorses “red-colored urine” for the past day. He just returned from an extensive hiking trip in Colorado. A radiograph of the abdomen was unremarkable. What is the most likely explanation for this patient’s presentation?

usmle-12836

A healthy 19-year-old man presents to his primary care provider complaining of painless “blisters” in his mouth. He reports that he noticed a white film on his tongue and the sides of his mouth 2 days ago while brushing his teeth. The film was easily brushed off. He also complains of a bitter metallic taste in his mouth but otherwise denies pain, burning, dysphagia, or hoarseness. He is otherwise healthy and takes no medications. He is a competitive swimmer and has had 8 sexual partners in the past year. He intermittently uses barrier protection. On exam, he is well-appearing and in no acute distress. His oral examination demonstrates patches of white pseudomembranes that can be wiped away to reveal erythematous mucosa. A medication with which of the following mechanisms of action is most appropriate in this patient?

usmle-12837

A 6-year-old female from a rural village in Afghanistan presents with her mother to a local health center complaining of leg weakness. Her mother also reports that the patient had a fever, fatigue, and headache a week prior that resolved. The patient has not received any immunizations since being born. Her temperature is 98.6°F (37°C), blood pressure is 110/70 mmHg, pulse is 90/min, and respirations are 18/min. Physical examination reveals 1/5 strength in right hip and knee actions and 0/5 strength in left hip and knee actions. Tone is notably decreased in both lower extremities. Sensation to touch, temperature, and vibration is intact. Patellar and Achilles reflexes are absent bilaterally. The most likely cause of this patient’s condition has which of the following characteristics?

usmle-12838

A 24-year-old woman with no past medical history presents to her PCP for a routine checkup. She feels generally healthy but has noticed a new vaginal discharge that has a strange odor. The patient has been in a long-term relationship and denies any new sexual partners. She denies vaginal itching, abnormal menstruation, or dyspareunia. Vital signs are within normal limits. The physical exam reveals thin, greyish-white vaginal discharge but is otherwise unremarkable. A sample of this discharge is collected. What would be the most likely finding on wet mount?

usmle-12839

A 40-year-old woman comes to the gynecologist with complaints of multiple genital lesions. She first noticed them a few weeks ago and hoped they would go away, but they have persisted. The growths are pruritic but have not bled or caused pain. She is currently sexually active with two men and engages in vaginal and anal intercourse. Genital examination is shown in Figure A. She is concerned that these growths are cancerous. Which of the following is the most likely pathogen associated with these lesions?

usmle-12840

A 9-year-old boy is brought to the clinic by his parents to establish care. The family recently moved from Canada and would like to find a primary care physician to manage his various health concerns. The patient was diagnosed with autism spectrum disorder (ASD) at the age of 4 and has since been undergoing behavioral therapy with moderate success. However, the patient had his first seizure 1 year ago and has been having breakthrough seizures despite treatment with levetiracetam. The mother claims that he has “calcium in his brain” based on past computed tomography scans of the head. A physical examination demonstrates a timid boy with poor interaction and an unremarkable physical exam. A skin finding is present on the lower back and is shown in Figure A. What mutation is responsible for causing this patient’s symptoms?

usmle-12841

A 42-year-old homeless male presents with fever and cough. He was found unconscious on the side of the road and was brought to the emergency room. He is noticeably drunk and is unable to answer any questions. On physical exam his temperature is 103°F (40°C), blood pressure is 130/85 mmHg, pulse is 110/min, respirations are 23/min, and pulse oximetry is 96% on room air. You note decreased breath sounds in the right lower lobe. The pathogen most likely responsible for this patient's symptoms has which of the following features?

usmle-12842

A 36-year-old woman is brought to the emergency room for altered mental status and rapid twitching of her left hand 3 hours ago. The patient is a poor historian given her current mental status, and her husband provided most of the history. He reports that the patient started demonstrating bizarre behavior about 2 weeks ago. She would be up until late into the night working on a “genius project” she had and had elaborate plans to double their joint investments. This morning, she began having speech difficulties, and her left hand jerked uncontrollably for the 10 minutes. He denies loss of consciousness, urinary incontinence, vision changes, or sick contacts. Her past medical history is significant for an adequately treated syphilis infection 10 years ago. Her temperature is 101°F (38.3°C), blood pressure is 118/70 mmHg, pulse is 103/min, respirations are 18/min, and oxygen saturation is 99% on room air. A physical examination demonstrates a lethargic individual with neck stiffness. A computed tomography of the head is unremarkable, and a cerebral spinal fluid (CSF) study is shown below. Cell count: 760/mm3 Cell type: Lymphocytes Glucose: 60 mg/dL Pressure: 100 mmH2O Proteins: 35 mg/dL Erythrocytes: 130/mm^3 What is the most likely explanation for this patient’s symptoms?

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A 60-year-old African American woman presents to her ophthalmologist with blurry vision. She reports a 2-month history of decreased vision primarily affecting her right eye. Her past medical history is notable for type 1 diabetes and hypertension. She takes insulin and enalapril. She has a 40-pack-year smoking history and drinks a glass of wine at dinner each night. Her family history is notable for glaucoma in her mother and severe diabetes complicated by nephropathy and retinopathy in her father. Her temperature is 99°F (37.2°C), blood pressure is 134/82 mmHg, pulse is 88/min, and respirations are 18/min. On exam, she is well-appearing and in no acute distress. The physician asks the patient to look forward and shines a penlight first in one eye, then the other, alternating quickly to observe the pupillary response to the light. When the light is shined in the right eye, both pupils partially constrict. When the light is shined in the left eye, both pupils constrict further. When the light is moved back to the right eye, both eyes dilate slightly to a partially constricted state. Where is the most likely site of this patient’s lesion?

usmle-12844

An 18-year-old female returning from a trip to a developing country presents with diarrhea and pain in the abdominal region. Microscopic evaluation of the stool reveals the presence of RBC's and WBC's. The patient reports poor sewage sanitation in the region she visited. The physician suspects a bacterial infection and culture reveals Gram-negative rods that are non-lactose fermenting. The A subunit of the bacteria's toxin acts to:

usmle-12845

An 8-year-old boy is brought to his pediatrician with a rash as seen in Figure A. He says that the rash is very itchy and bothers him; however, he denies have any other symptoms such as fever or night sweats. He has never had these kinds of symptoms prior to this occurrence. Notably, several of his classmates have had similar symptoms over the course of the last few months. Based on clinical suspicion, a stained smear of the rash is obtained showing the histology in seen in Figure B. Which type of vaccine would most likely have protected this patient from this disease?

usmle-12846

A 35-year-old female presents to the clinic for a red rash over her right thigh for the past 2 days. She reports a bug bite at the area a couple of days ago when she was hiking. It became itchy shortly after and she has been scratching the area ever since. A physical examination demonstrates a clearly-demarcated, erythematous area that is warm and tender upon palpation (Figure A). She is subsequently started on oral amoxicillin. During her follow-up appointment, she reports initial improvement, but that the rash is persisting. A culture of the skin lesion is positive for methicillin-sensitive Staphylococcal aureus (MSSA). She is started on nafcillin. What characteristic of this drug allows for more targeted treatment of this patient’s condition?

usmle-12847

A 35-year-old male is found to be infected with an HIV strain resistant to saquinavir and zidovudine. Which of the following best explains the drug resistance observed in this patient?

usmle-12848

An 8-year-old child with “elfin” facial features is very friendly with strangers. He has a history of mild mental retardation, and a hemizygous deletion on chromosome 7q11.23, that includes a portion of the elastin gene. Which of the following is most likely true in this patient?

usmle-12849

A 31-year-old male traveler in Thailand experiences fever, headache, and excessive sweating every 48 hours. Peripheral blood smear shows trophozoites and schizonts indicative of Plasmodia infection. The patient is given chloroquine and primaquine. Primaquine targets which of the following Plasmodia forms:

usmle-12850

A 29-year-old woman comes to the clinic complaining of headache and cough for the past 3 days. She thought that she had a common cold, but she is feeling progressively worse and decided to come to the emergency room today. She reports a nonproductive cough, sore throat, rhinorrhea, and shortness of breath but denies fever, chills, chest pain, or abdominal pain. Her past medical history is significant for asthma that is well controlled with albuterol. A physical examination demonstrates mild tenderness of the right lower chest upon palpation and mild rales and wheezes in the bibasilar lung fields. A chest radiograph is obtained and its results are shown in Figure A. Laboratory studies are shown below: Hemoglobin: 9.1 g/dL Hematocrit: 39% Leukocyte count: 7,400/mm^3 with normal differential Platelet count: 160,000/mm^3 Serum: Na+: 137 mEq/L Cl-: 97 mEq/L K+: 3.8 mEq/L HCO3-: 25 mEq/L BUN: 8 mg/dL Glucose: 117 mg/dL Creatinine: 0.4 mg/dL Thyroid-stimulating hormone: 4.1 µU/mL Ca2+: 9.2 mg/dL AST: 16 U/L ALT: 15 U/L What is the most likely explanation of this patient’s presentation?