bowang0911/MedQuAD huggingface dataset:
X-linked infantile spasm syndrome can have different inheritance patterns depending on the genetic cause.  When caused by mutations in the ARX gene, this condition is inherited in an X-linked recessive pattern. The ARX gene is located on the X chromosome, which is one of the two sex chromosomes. In males (who have only one X chromosome), one altered copy of the gene in each cell is sufficient to cause the condition. Usually in females (who have two X chromosomes), a mutation would have to occur in both copies of the gene to cause the disorder. However, in some instances, one altered copy of the ARX gene is sufficient because the X chromosome with the normal copy of the ARX gene is turned off through a process called X-inactivation. Early in embryonic development in females, one of the two X chromosomes is permanently inactivated in somatic cells (cells other than egg and sperm cells). X-inactivation ensures that females, like males, have only one active copy of the X chromosome in each body cell. Usually X-inactivation occurs randomly, such that each X chromosome is active in about half of the body cells. Sometimes X-inactivation is not random, and one X chromosome is active in more than half of cells. When X-inactivation does not occur randomly, it is called skewed X-inactivation. Some ARX gene mutations may be associated with skewed X-inactivation, which results in the inactivation of the X chromosome with the normal copy of the ARX gene in most cells of the body. This skewed X-inactivation causes the chromosome with the mutated ARX gene to be expressed in more than half of cells, causing X-linked infantile spasm syndrome.  When caused by mutations in the CDKL5 gene, this condition is thought to have an X-linked dominant inheritance pattern. The CDKL5 gene is also located on the X chromosome, making this condition X-linked. The inheritance is dominant because one copy of the altered gene in each cell is sufficient to cause the condition in both males and females.  X-linked infantile spasm syndrome caused by CDKL5 gene mutations usually occurs in individuals with no history of the disorder in their family. These mutations likely occur in early embryonic development (called de novo mutations). Because males have only one X chromosome, X-linked dominant disorders are often more severe in males than in females. Male fetuses with CDKL5-related X-linked infantile spasm syndrome may not survive to birth, so more females are diagnosed with the condition. In females, the distribution of active and inactive X chromosomes due to X-inactivation may affect whether a woman develops the condition or the severity of the signs and symptoms. Generally, the larger the proportion of active X chromosomes that contain the mutated CDKL5 gene, the more severe the signs and symptoms of the condition are.  A characteristic of X-linked inheritance is that fathers cannot pass X-linked traits to their sons.
These resources address the diagnosis or management of X-linked infantile spasm syndrome:  - Child Neurology Foundation  - Genetic Testing Registry: Early infantile epileptic encephalopathy 2  - Genetic Testing Registry: West syndrome   These resources from MedlinePlus offer information about the diagnosis and management of various health conditions:  - Diagnostic Tests  - Drug Therapy  - Surgery and Rehabilitation  - Genetic Counseling   - Palliative Care
Knobloch syndrome is a rare condition characterized by severe vision problems and a skull defect.  A characteristic feature of Knobloch syndrome is extreme nearsightedness (high myopia). In addition, several other eye abnormalities are common in people with this condition. Most affected individuals have vitreoretinal degeneration, which is breakdown (degeneration) of two structures in the eye called the vitreous and the retina. The vitreous is the gelatin-like substance that fills the eye, and the retina is the light-sensitive tissue at the back of the eye. Vitreoretinal degeneration often leads to separation of the retina from the back of the eye (retinal detachment). Affected individuals may also have abnormalities in the central area of the retina, called the macula. The macula is responsible for sharp central vision, which is needed for detailed tasks such as reading, driving, and recognizing faces. Due to abnormalities in the vitreous, retina, and macula, people with Knobloch syndrome often develop blindness in one or both eyes.  Another characteristic feature of Knobloch syndrome is a skull defect called an occipital encephalocele, which is a sac-like protrusion of the brain (encephalocele) through a defect in the bone at the base of the skull (occipital bone). Some affected individuals have been diagnosed with a different skull defect in the occipital region, and it is unclear whether the defect is always a true encephalocele. In other conditions, encephaloceles may be associated with intellectual disability; however, most people with Knobloch syndrome have normal intelligence.
Mutations in the COL18A1 gene can cause Knobloch syndrome. The COL18A1 gene provides instructions for making a protein that forms collagen XVIII, which is found in the basement membranes of tissues throughout the body. Basement membranes are thin, sheet-like structures that separate and support cells in these tissues. Collagen XVIII is found in the basement membranes of several parts of the eye, including the vitreous and retina, among other tissues. Little is known about the function of this protein, but it appears to be involved in normal development of the eye.  Several mutations in the COL18A1 gene have been identified in people with Knobloch syndrome. Most COL18A1 gene mutations lead to an abnormally short version of the genetic blueprint used to make the collagen XVIII protein. Although the process is unclear, the COL18A1 gene mutations result in the loss of collagen XVIII protein, which likely causes the signs and symptoms of Knobloch syndrome.  When the condition is caused by COL18A1 gene mutations, it is sometimes referred to as Knobloch syndrome type I. Research indicates that mutations in at least two other genes that have not been identified may cause Knobloch syndrome types II and III. Although they are caused by alterations in different genes, the three types of the condition have similar signs and symptoms.
These resources address the diagnosis or management of Knobloch syndrome:  - American Academy of Ophthalmology: Eye Smart  - Genetic Testing Registry: Knobloch syndrome 1  - JAMA Patient Page: Retinal Detachment  - National Eye Institute: Facts About Retinal Detachment  - Prevent Blindness America: Retinal Tears and Detachments   These resources from MedlinePlus offer information about the diagnosis and management of various health conditions:  - Diagnostic Tests  - Drug Therapy  - Surgery and Rehabilitation  - Genetic Counseling   - Palliative Care
Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN) is a severe skin reaction most often triggered by particular medications. Although Stevens-Johnson syndrome and toxic epidermal necrolysis were once thought to be separate conditions, they are now considered part of a continuum. Stevens-Johnson syndrome represents the less severe end of the disease spectrum, and toxic epidermal necrolysis represents the more severe end.  SJS/TEN often begins with a fever and flu-like symptoms. Within a few days, the skin begins to blister and peel, forming very painful raw areas called erosions that resemble a severe hot-water burn. The skin erosions usually start on the face and chest before spreading to other parts of the body. In most affected individuals, the condition also damages the mucous membranes, including the lining of the mouth and the airways, which can cause trouble with swallowing and breathing. The painful blistering can also affect the urinary tract and genitals. SJS/TEN often affects the eyes as well, causing irritation and redness of the conjunctiva, which are the mucous membranes that protect the white part of the eye and line the eyelids, and damage to the clear front covering of the eye (the cornea).  Severe damage to the skin and mucous membranes makes SJS/TEN a life-threatening disease. Because the skin normally acts as a protective barrier, extensive skin damage can lead to a dangerous loss of fluids and allow infections to develop. Serious complications can include pneumonia, overwhelming bacterial infections (sepsis), shock, multiple organ failure, and death. About 10 percent of people with Stevens-Johnson syndrome die from the disease, while the condition is fatal in up to 50 percent of those with toxic epidermal necrolysis.  Among people who survive, long-term effects of SJS/TEN can include changes in skin coloring (pigmentation), dryness of the skin and mucous membranes (xerosis), excess sweating (hyperhidrosis), hair loss (alopecia), and abnormal growth or loss of the fingernails and toenails. Other long-term problems can include impaired taste, difficulty urinating, and genital abnormalities. A small percentage of affected individuals develop chronic dryness or inflammation of the eyes, which can lead to increased sensitivity to light (photophobia) and vision impairment.
SJS/TEN is a rare disease, affecting 1 to 2 per million people each year. Stevens-Johnson syndrome (the less severe form of the condition) is more common than toxic epidermal necrolysis.  People who are HIV-positive and those with a chronic inflammatory disease called systemic lupus erythematosus are more likely to develop SJS/TEN than the general population. The reason for the increased risk is unclear, but immune system factors and exposure to multiple medications may play a role.
Several genetic changes have been found to increase the risk of SJS/TEN in response to triggering factors such as medications. Most of these changes occur in genes that are involved in the normal function of the immune system.  The genetic variations most strongly associated with SJS/TEN occur in the HLA-B gene. This gene is part of a family of genes called the human leukocyte antigen (HLA) complex. The HLA complex helps the immune system distinguish the body's own proteins from proteins made by foreign invaders (such as viruses and bacteria). The HLA-B gene has many different normal variations, allowing each person's immune system to react to a wide range of foreign proteins. Certain variations in this gene occur much more often in people with SJS/TEN than in people without the condition.  Studies suggest that the HLA-B gene variations associated with SJS/TEN cause the immune system to react abnormally to certain medications. In a process that is not well understood, the drug causes immune cells called cytotoxic T cells and natural killer (NK) cells to release a substance called granulysin that destroys cells in the skin and mucous membranes. The death of these cells causes the blistering and peeling that is characteristic of SJS/TEN.  Variations in several other HLA and non-HLA genes have also been studied as potential risk factors for SJS/TEN. However, most people with genetic variations that increase the risk of SJS/TEN never develop the disease, even if they are exposed to drugs that can trigger it. Researchers believe that additional genetic and nongenetic factors, many of which are unknown, likely play a role in whether a particular individual develops SJS/TEN.  The drugs most frequently associated with SJS/TEN include several medications that are used to treat seizures (particularly carbamazepine, lamotrigine, and phenytoin); allopurinol, which is used to treat kidney stones and a form of arthritis called gout; a class of antibiotic drugs called sulfonamides; nevirapine, which is used to treat HIV infection; and a type of non-steroidal anti-inflammatory drugs (NSAIDs) called oxicams. Other factors may also trigger SJS/TEN. In particular, these skin reactions have occurred in people with an unusual form of pneumonia caused by infection with Mycoplasma pneumoniae and in people with viral infections, including cytomegalovirus. Researchers suspect that a combination of infections and drugs could contribute to the disease in some individuals. In many cases, no definitive trigger for an individual's SJS/TEN is ever discovered.
Benign recurrent intrahepatic cholestasis (BRIC) is characterized by episodes of liver dysfunction called cholestasis. During these episodes, the liver cells have a reduced ability to release a digestive fluid called bile. Because the problems with bile release occur within the liver (intrahepatic), the condition is described as intrahepatic cholestasis. Episodes of cholestasis can last from weeks to months, and the time between episodes, during which there are usually no symptoms, can vary from weeks to years.  The first episode of cholestasis usually occurs in an affected person's teens or twenties. An attack typically begins with severe itchiness (pruritus), followed by yellowing of the skin and whites of the eyes (jaundice) a few weeks later. Other general signs and symptoms that occur during these episodes include a vague feeling of discomfort (malaise), irritability, nausea, vomiting, and a lack of appetite. A common feature of BRIC is the reduced absorption of fat in the body, which leads to excess fat in the feces (steatorrhea). Because of a lack of fat absorption and loss of appetite, affected individuals often lose weight during episodes of cholestasis.  BRIC is divided into two types, BRIC1 and BRIC2, based on the genetic cause of the condition. The signs and symptoms are the same in both types.  This condition is called benign because it does not cause lasting damage to the liver. However, episodes of liver dysfunction occasionally develop into a more severe, permanent form of liver disease known as progressive familial intrahepatic cholestasis (PFIC). BRIC and PFIC are sometimes considered to be part of a spectrum of intrahepatic cholestasis disorders of varying severity.
Mutations in the ATP8B1 gene cause benign recurrent intrahepatic cholestasis type 1 (BRIC1), and mutations in the ABCB11 gene cause benign recurrent intrahepatic cholestasis type 2 (BRIC2). These two genes are involved in the release (secretion) of bile, a fluid produced by the liver that helps digest fats.  The ATP8B1 gene provides instructions for making a protein that helps to control the distribution of certain fats, called lipids, in the membranes of liver cells. This function likely plays a role in maintaining an appropriate balance of bile acids, a component of bile. This process, known as bile acid homeostasis, is critical for the normal secretion of bile and the proper functioning of liver cells. Although the mechanism is unclear, mutations in the ATP8B1 gene result in the buildup of bile acids in liver cells. The imbalance of bile acids leads to the signs and symptoms of BRIC1.  The ABCB11 gene provides instructions for making a protein called the bile salt export pump (BSEP). This protein is found in the liver, and its main role is to move bile salts (a component of bile) out of liver cells. Mutations in the ABCB11 gene result in a reduction of BSEP function. This reduction leads to a decrease of bile salt secretion, which causes the features of BRIC2.  The factors that trigger episodes of BRIC are unknown.  Some people with BRIC do not have a mutation in the ATP8B1 or ABCB11 gene. In these individuals, the cause of the condition is unknown.
Both types of BRIC are inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.  Some people with BRIC have no family history of the disorder. These cases arise from mutations in the ATP8B1 or ABCB11 gene that occur in the body's cells after conception and are not inherited.
These resources address the diagnosis or management of benign recurrent intrahepatic cholestasis:  - Gene Review: Gene Review: ATP8B1 Deficiency  - Genetic Testing Registry: Benign recurrent intrahepatic cholestasis 1  - Genetic Testing Registry: Benign recurrent intrahepatic cholestasis 2  - Merck Manual Home Health Edition: Cholestasis   These resources from MedlinePlus offer information about the diagnosis and management of various health conditions:  - Diagnostic Tests  - Drug Therapy  - Surgery and Rehabilitation  - Genetic Counseling   - Palliative Care
Wilson disease is an inherited disorder in which excessive amounts of copper accumulate in the body, particularly in the liver, brain, and eyes. The signs and symptoms of Wilson disease usually first appear between the ages of 6 and 45, but they most often begin during the teenage years. The features of this condition include a combination of liver disease and neurological and psychiatric problems.  Liver disease is typically the initial feature of Wilson disease in affected children and young adults; individuals diagnosed at an older age usually do not have symptoms of liver problems, although they may have very mild liver disease. The signs and symptoms of liver disease include yellowing of the skin or whites of the eyes (jaundice), fatigue, loss of appetite, and abdominal swelling.  Nervous system or psychiatric problems are often the initial features in individuals diagnosed in adulthood and commonly occur in young adults with Wilson disease. Signs and symptoms of these problems can include clumsiness, tremors, difficulty walking, speech problems, impaired thinking ability, depression, anxiety, and mood swings.  In many individuals with Wilson disease, copper deposits in the front surface of the eye (the cornea) form a green-to-brownish ring, called the Kayser-Fleischer ring, that surrounds the colored part of the eye. Abnormalities in eye movements, such as a restricted ability to gaze upwards, may also occur.
Wilson disease is caused by mutations in the ATP7B gene. This gene provides instructions for making a protein called copper-transporting ATPase 2, which plays a role in the transport of copper from the liver to other parts of the body. Copper is necessary for many cellular functions, but it is toxic when present in excessive amounts. The copper-transporting ATPase 2 protein is particularly important for the elimination of excess copper from the body. Mutations in the ATP7B gene prevent the transport protein from functioning properly. With a shortage of functional protein, excess copper is not removed from the body. As a result, copper accumulates to toxic levels that can damage tissues and organs, particularly the liver and brain.  Research indicates that a normal variation in the PRNP gene may modify the course of Wilson disease. The PRNP gene provides instructions for making prion protein, which is active in the brain and other tissues and appears to be involved in transporting copper. Studies have focused on the effects of a PRNP gene variation that affects position 129 of the prion protein. At this position, people can have either the protein building block (amino acid) methionine or the amino acid valine. Among people who have mutations in the ATP7B gene, it appears that having methionine instead of valine at position 129 of the prion protein is associated with delayed onset of symptoms and an increased occurrence of neurological symptoms, particularly tremors. Larger studies are needed, however, before the effects of this PRNP gene variation on Wilson disease can be established.
These resources address the diagnosis or management of Wilson disease:  - Gene Review: Gene Review: Wilson Disease  - Genetic Testing Registry: Wilson's disease  - MedlinePlus Encyclopedia: Wilson's disease  - National Human Genome Research Institute   These resources from MedlinePlus offer information about the diagnosis and management of various health conditions:  - Diagnostic Tests  - Drug Therapy  - Surgery and Rehabilitation  - Genetic Counseling   - Palliative Care
Beta thalassemia is a blood disorder that reduces the production of hemoglobin. Hemoglobin is the iron-containing protein in red blood cells that carries oxygen to cells throughout the body.  In people with beta thalassemia, low levels of hemoglobin lead to a lack of oxygen in many parts of the body. Affected individuals also have a shortage of red blood cells (anemia), which can cause pale skin, weakness, fatigue, and more serious complications. People with beta thalassemia are at an increased risk of developing abnormal blood clots.  Beta thalassemia is classified into two types depending on the severity of symptoms: thalassemia major (also known as Cooley's anemia) and thalassemia intermedia. Of the two types, thalassemia major is more severe.  The signs and symptoms of thalassemia major appear within the first 2 years of life. Children develop life-threatening anemia. They do not gain weight and grow at the expected rate (failure to thrive) and may develop yellowing of the skin and whites of the eyes (jaundice). Affected individuals may have an enlarged spleen, liver, and heart, and their bones may be misshapen. Some adolescents with thalassemia major experience delayed puberty. Many people with thalassemia major have such severe symptoms that they need frequent blood transfusions to replenish their red blood cell supply. Over time, an influx of iron-containing hemoglobin from chronic blood transfusions can lead to a buildup of iron in the body, resulting in liver, heart, and hormone problems.  Thalassemia intermedia is milder than thalassemia major. The signs and symptoms of thalassemia intermedia appear in early childhood or later in life. Affected individuals have mild to moderate anemia and may also have slow growth and bone abnormalities.
Mutations in the HBB gene cause beta thalassemia. The HBB gene provides instructions for making a protein called beta-globin. Beta-globin is a component (subunit) of hemoglobin. Hemoglobin consists of four protein subunits, typically two subunits of beta-globin and two subunits of another protein called alpha-globin.  Some mutations in the HBB gene prevent the production of any beta-globin. The absence of beta-globin is referred to as beta-zero (B0) thalassemia. Other HBB gene mutations allow some beta-globin to be produced but in reduced amounts. A reduced amount of beta-globin is called beta-plus (B+) thalassemia. Having either B0 or B+ thalassemia does not necessarily predict disease severity, however; people with both types have been diagnosed with thalassemia major and thalassemia intermedia.  A lack of beta-globin leads to a reduced amount of functional hemoglobin. Without sufficient hemoglobin, red blood cells do not develop normally, causing a shortage of mature red blood cells. The low number of mature red blood cells leads to anemia and other associated health problems in people with beta thalassemia.
Thalassemia major and thalassemia intermedia are inherited in an autosomal recessive pattern, which means both copies of the HBB gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition. Sometimes, however, people with only one HBB gene mutation in each cell develop mild anemia. These mildly affected people are said to have thalassemia minor.  In a small percentage of families, the HBB gene mutation is inherited in an autosomal dominant manner. In these cases, one copy of the altered gene in each cell is sufficient to cause the signs and symptoms of beta thalassemia.
These resources address the diagnosis or management of beta thalassemia:  - Gene Review: Gene Review: Beta-Thalassemia  - Genetic Testing Registry: Beta-thalassemia, dominant inclusion body type  - Genetic Testing Registry: beta Thalassemia  - MedlinePlus Encyclopedia: Thalassemia   These resources from MedlinePlus offer information about the diagnosis and management of various health conditions:  - Diagnostic Tests  - Drug Therapy  - Surgery and Rehabilitation  - Genetic Counseling   - Palliative Care