bowang0911/MedQuAD huggingface dataset:
The exact cause of asthma isn't known. Researchers think some genetic and environmental factors interact to cause asthma, most often early in life. These factors include:
                
An inherited tendency to develop allergies, called atopy (AT-o-pe)
                
Parents who have asthma
                
Certain respiratory infections during childhood
                
Contact with some airborne allergens or exposure to some viral infections in infancy or in early childhood when the immune system is developing
                
If asthma or atopy runs in your family, exposure to irritants (for example, tobacco smoke) may make your airways more reactive to substances in the air.
                
Some factors may be more likely to cause asthma in some people than in others. Researchers continue to explore what causes asthma.
                
The "Hygiene Hypothesis"
                
One theory researchers have for what causes asthma is the "hygiene hypothesis." They believe that our Western lifestylewith its emphasis on hygiene and sanitationhas resulted in changes in our living conditions and an overall decline in infections in early childhood.
                
Many young children no longer have the same types of environmental exposures and infections as children did in the past. This affects the way that young children's immune systems develop during very early childhood, and it may increase their risk for atopy and asthma. This is especially true for children who have close family members with one or both of these conditions.
Asthma affects people of all ages, but it most often starts during childhood. In the United States, more than 22 million people are known to have asthma. Nearly 6 million of these people are children.
                
Young children who often wheeze and have respiratory infectionsas well as certain other risk factorsare at highest risk of developing asthma that continues beyond 6 years of age. The other risk factors include having allergies, eczema (an allergic skin condition), or parents who have asthma.
                
Among children, more boys have asthma than girls. But among adults, more women have the disease than men. It's not clear whether or how sex and sex hormones play a role in causing asthma.
                
Most, but not all, people who have asthma have allergies.
                
Some people develop asthma because of contact with certain chemical irritants or industrial dusts in the workplace. This type of asthma is called occupational asthma.
Common signs and symptoms of asthma include:
                
Coughing. Coughing from asthma often is worse at night or early in the morning, making it hard to sleep.
                
Wheezing. Wheezing is a whistling or squeaky sound that occurs when you breathe.
                
Chest tightness. This may feel like something is squeezing or sitting on your chest.
                
Shortness of breath. Some people who have asthma say they can't catch their breath or they feel out of breath. You may feel like you can't get air out of your lungs.
                
Not all people who have asthma have these symptoms. Likewise, having these symptoms doesn't always mean that you have asthma. The best way to diagnose asthma for certain is to use a lung function test, a medical history (including type and frequency of symptoms), and a physical exam.
                
The types of asthma symptoms you have, how often they occur, and how severe they are may vary over time. Sometimes your symptoms may just annoy you. Other times, they may be troublesome enough to limit your daily routine.
                
Severe symptoms can be fatal. It's important to treat symptoms when you first notice them so they don't become severe.
                
With proper treatment, most people who have asthma can expect to have few, if any, symptoms either during the day or at night.
                
What Causes Asthma Symptoms To Occur?
                
Many things can trigger or worsen asthma symptoms. Your doctor will help you find out which things (sometimes called triggers) may cause your asthma to flare up if you come in contact with them. Triggers may include:
                
Allergens from dust, animal fur, cockroaches, mold, and pollens from trees, grasses, and flowers
                
Irritants such as cigarette smoke, air pollution, chemicals or dust in the workplace, compounds in home dcor products, and sprays (such as hairspray)
                
Medicines such as aspirin or other nonsteroidal anti-inflammatory drugs and nonselective beta-blockers
                
Sulfites in foods and drinks
                
Viral upper respiratory infections, such as colds
                
Physical activity, including exercise
                
Other health conditions can make asthma harder to manage. Examples of these conditions include a runny nose, sinus infections, reflux disease, psychological stress, and sleep apnea. These conditions need treatment as part of an overall asthma care plan.
                
Asthma is different for each person. Some of the triggers listed above may not affect you. Other triggers that do affect you may not be on the list. Talk with your doctor about the things that seem to make your asthma worse.
You cant prevent asthma. However, you can take steps to control the disease and prevent its symptoms. For example:
                
Learn about your asthma and ways to control it.
                
Follow your written asthma action plan. (For a sample plan, go to the National Heart, Lung, and Blood Institute's "Asthma Action Plan.")
                
Use medicines as your doctor prescribes.
                
Identify and try to avoid things that make your asthma worse (asthma triggers). However, one trigger you should not avoid is physical activity. Physical activity is an important part of a healthy lifestyle. Talk with your doctor about medicines that can help you stay active.
                
Keep track of your asthma symptoms and level of control.
                
Get regular checkups for your asthma.
                
For more details about how to prevent asthma symptoms and attacks, go to "How Is Asthma Treated and Controlled?"
Patent ductus arteriosus (PDA) is a heart problem that occurs soon after birth in some babies. In PDA, abnormal blood flow occurs between two of the major arteries connected to the heart.
                
Before birth, the two major arteriesthe aorta and the pulmonary (PULL-mun-ary) arteryare connected by a blood vessel called the ductus arteriosus. This vessel is an essential part of fetal blood circulation.
                
Within minutes or up to a few days after birth, the vessel is supposed to close as part of the normal changes occurring in the baby's circulation.
                
In some babies, however, the ductus arteriosus remains open (patent). This opening allows oxygen-rich blood from the aorta to mix with oxygen-poor blood from the pulmonary artery. This can put strain on the heart and increase blood pressure in the lung arteries.
                
Normal Heart and Heart With Patent Ductus Arteriosus
                

                
Go to the "How the Heart Works" section of this article for more details about how a normal heart works compared with a heart that has PDA.
                
Overview
                
PDA is a type of congenital (kon-JEN-ih-tal) heart defect. A congenital heart defect is any type of heart problem that's present at birth.
                
If your baby has a PDA but an otherwise normal heart, the PDA may shrink and go away. However, some children need treatment to close their PDAs.
                
Some children who have PDAs are given medicine to keep the ductus arteriosus open. For example, this may be done if a child is born with another heart defect that decreases blood flow to the lungs or the rest of the body.
                
Keeping the PDA open helps maintain blood flow and oxygen levels until doctors can do surgery to correct the other heart defect.
                
Outlook
                
PDA is a fairly common congenital heart defect in the United States. Although the condition can affect full-term infants, it's more common in premature infants.
                
On average, PDA occurs in about 8 out of every 1,000 premature babies, compared with 2out of every 1,000 full-term babies. Premature babies also are more vulnerable to the effects of PDA.
                
PDA is twice as common in girls as it is in boys.
                
Doctors treat the condition with medicines, catheter-based procedures, and surgery. Most children who have PDAs live healthy, normal lives after treatment.
Patent ductus arteriosus (PDA) is a relatively common congenital heart defect in the United States.
                
The condition occurs more often in premature infants (on average, occurring in about 8 of every 1,000 births). However, PDA also occurs in full-term infants (on average, occurring in about 2 of every 1,000 births).
                
PDA also is more common in:
                
Infants who have genetic conditions such as Down syndrome
                
Infants whose mothers had German measles (rubella) during pregnancy
                
PDA is twice as common in girls as it is in boys.
A heart murmur may be the only sign that a baby has patent ductus arteriosus (PDA). A heart murmur is an extra or unusual sound heard during the heartbeat. Heart murmurs also have other causes besides PDA, and most murmurs are harmless.
                
Some infants may develop signs or symptoms of volume overload on the heart and excess blood flow in the lungs. Signs and symptoms may include:
                
Fast breathing, working hard to breathe, or shortness of breath. Premature infants may need increased oxygen or help breathing from a ventilator.
                
Poor feeding and poor weight gain.
                
Tiring easily.
                
Sweating with exertion, such as while feeding.
In full-term infants, patent ductus arteriosus (PDA) usually is first suspected when the baby's doctor hears a heart murmur during a regular checkup.
                
A heart murmur is an extra or unusual sound heard during the heartbeat. Heart murmurs also have other causes besides PDA, and most murmurs are harmless.
                
If a PDA is large, the infant also may develop symptoms of volume overload and increased blood flow to the lungs. If a PDA is small, it may not be diagnosed until later in childhood.
                
If your child's doctor thinks your child has PDA, he or she may refer you to a pediatric cardiologist. This is a doctor who specializes in diagnosing and treating heart problems in children.
                
Premature babies who have PDA may not have the same signs as full-term babies, such as heart murmurs. Doctors may suspect PDA in premature babies who develop breathing problems soon after birth. Tests can help confirm a diagnosis.
                
Diagnostic Tests
                
Echocardiography
                
Echocardiography (echo) is a painless test that uses sound waves to create a moving picture of your baby's heart. During echo, the sound waves bounce off your childs heart. A computer converts the sound waves into pictures of the hearts structures.
                
The test allows the doctor to clearly see any problems with the way the heart is formed or the way it's working. Echo is the most important test available to your baby's cardiologist to both diagnose a heart problem and follow the problem over time.
                
In babies who have PDA, echo shows how big the PDA is and how well the heart is responding to it. When medical treatments are used to try to close a PDA, echo is used to see how well the treatments are working.
                
EKG (Electrocardiogram)
                
An EKG is a simple, painless test that records the heart's electrical activity. For babies who have PDA, an EKG can show whether the heart is enlarged. The test also can show other subtle changes that can suggest the presence of a PDA.
Abnormal hemoglobin, called hemoglobin S, causes sickle cell disease (SCD).
                
The problem in hemoglobin S is caused by a small defect in the gene that directs the production of the beta globin part of hemoglobin. This small defect in the beta globin gene causes a problem in the beta globin part of hemoglobin, changing the way that hemoglobin works. (See Overview.)
                

                
How Is Sickle Cell Disease Inherited?
                
When the hemoglobin S gene is inherited from only one parent and a normal hemoglobin gene is inherited from the other, a person will have sickle cell trait. People with sickle cell trait are generally healthy.
                
Only rarely do people with sickle cell trait have complications similar to those seen in people with SCD. But people with sickle cell trait are carriers of a defective hemoglobin S gene. So, they can pass it on when they have a child.
                
If the childs other parent also has sickle cell trait or another abnormal hemoglobin gene (like thalassemia, hemoglobin C, hemoglobin D, hemoglobin E), that child has a chance of having SCD.
                
Example of an Inheritance Pattern
                

                
In the image above, each parent has one hemoglobin A gene and one hemoglobin S gene, and each of their children has:
                
A 25 percent chance of inheriting two normal genes: In this case the child does not have sickle cell trait or disease. (Case 1)
                
A 50 percent chance of inheriting one hemoglobin A gene and one hemoglobin S gene: This child has sickle cell trait. (Cases 2 and 3)
                
A 25 percent chance of inheriting two hemoglobin S genes: This child has sickle cell disease. (Case 4)
                
It is important to keep in mind that each time this couple has a child, the chances of that child having sickle cell disease remain the same. In other words, if the first-born child has sickle cell disease, there is still a 25 percent chance that the second child will also have the disease. Both boys and girls can inherit sickle cell trait, sickle cell disease, or normal hemoglobin.
                
If a person wants to know if he or she carries a sickle hemoglobin gene, a doctor can order a blood test to find out.
In the United States, most people with sickle cell disease (SCD) are of African ancestry or identify themselves as black.
                
About 1 in 13 African American babies is born with sickle cell trait.
                
About 1 in every 365 black children is born with sickle cell disease.
                
There are also many people with this disease who come from Hispanic, southern European, Middle Eastern, or Asian Indian backgrounds.
                
Approximately 100,000 Americans have SCD.
Screening Tests
                
People who do not know whether they make sickle hemoglobin (hemoglobin S) or another abnormal hemoglobin (such as C,  thalassemia, E) can find out by having their blood tested. This way, they can learn whether they carry a gene (i.e., have the trait) for an abnormal hemoglobin that they could pass on to a child.
                
When each parent has this information, he or she can be better informed about the chances of having a child with some type of sickle cell disease (SCD), such as hemoglobin SS, SC, S thalassemia, or others.
                
Newborn Screening
                
When a child has SCD, it is very important to diagnose it early to better prevent complications.
                
Every state in the United States, the District of Columbia, and the U.S. territories require that every baby is tested for SCD as part of a newborn screening program.
                
In newborn screening programs, blood from a heel prick is collected in spots on a special paper. The hemoglobin from this blood is then analyzed in special labs.
                
Newborn screening results are sent to the doctor who ordered the test and to the childs primary doctor.
                
If a baby is found to have SCD, health providers from a special follow-up newborn screening group contact the family directly to make sure that the parents know the results. The child is always retested to be sure that the diagnosis is correct.
                
Newborn screening programs also find out whether the baby has an abnormal hemoglobin trait. If so, parents are informed, and counseling is offered.
                
Remember that when a child has sickle cell trait or SCD, a future sibling, or the childs own future child, may be at risk. These possibilities should be discussed with the primary care doctor, a blood specialist called a hematologist, and/or a genetics counselor.
                
Prenatal Screening
                
Doctors can also diagnose SCD before a baby is born. This is done using a sample of amniotic fluid, the liquid in the sac surrounding a growing embryo, or tissue taken from the placenta, the organ that attaches the umbilical cord to the mothers womb.
                
Testing before birth can be done as early as 810 weeks into the pregnancy. This testing looks for the sickle hemoglobin gene rather than the abnormal hemoglobin.
Polycythemia vera (POL-e-si-THEE-me-ah VAY-rah or VE-rah), or PV, is a rare blood disease in which your body makes too many red blood cells.
                
The extra red blood cells make your blood thicker than normal. As a result, blood clots can form more easily. These clots can block blood flow through your arteries and veins, which can cause a heart attack or stroke.
                
Thicker blood also doesn't flow as quickly to your body as normal blood. Slowed blood flow prevents your organs from getting enough oxygen, which can cause serious problems, such as angina (an-JI-nuh or AN-juh-nuh) and heart failure. (Angina is chest pain or discomfort.)
                
Overview
                
Red blood cells carry oxygen to all parts of your body. They also remove carbon dioxide (a waste product) from your body's cells and carry it to the lungs to be exhaled.
                
Red blood cells are made in your bone marrowa sponge-like tissue inside the bones. White blood cells and platelets (PLATE-lets) also are made in your bone marrow. White blood cells help fight infection. Platelets stick together to seal small cuts or breaks on blood vessel walls and stop bleeding.
                
If you have PV, your bone marrow makes too many red blood cells. It also can make too many white blood cells and platelets.
                
A mutation, or change, in the body's JAK2 gene is the major cause of PV. This gene makes a protein that helps the body produce blood cells. What causes the change in the JAK2 gene isn't known. PV generally isn't inheritedthat is, passed from parents to children through genes.
                
PV develops slowly and may not cause symptoms for years. The disease often is found during routine blood tests done for other reasons.
                
When signs and symptoms are present, they're the result of the thick blood that occurs with PV. This thickness slows the flow of oxygen-rich blood to all parts of your body. Without enough oxygen, many parts of your body won't work normally.
                
For example, slower blood flow deprives your arms, legs, lungs, and eyes of the oxygen they need. This can cause headaches, dizziness, itching, and vision problems, such as blurred or double vision.
                
Outlook
                
PV is a serious, chronic (ongoing) disease that can be fatal if not diagnosed and treated. PV has no cure, but treatments can help control the disease and its complications.
                
PV is treated with procedures, medicines, and other methods. You may need one or more treatments to manage the disease.
Primary Polycythemia
                
Polycythemia vera (PV) also is known as primary polycythemia. A mutation, or change, in the body's JAK2 gene is the main cause of PV. The JAK2 gene makes a protein that helps the body produce blood cells.
                
What causes the change in the JAK2 gene isn't known. PV generally isn't inheritedthat is, passed from parents to children through genes. However, in some families, the JAK2 gene may have a tendency to mutate. Other, unknown genetic factors also may play a role in causing PV.
                
Secondary Polycythemia
                
Another type of polycythemia, called secondary polycythemia, isn't related to the JAK2 gene. Long-term exposure to low oxygen levels causes secondary polycythemia.
                
A lack of oxygen over a long period can cause your body to make more of the hormone erythropoietin (EPO). High levels of EPO can prompt your body to make more red blood cells than normal. This leads to thicker blood, as seen in PV.
                
People who have severe heart or lung disease may develop secondary polycythemia. People who smoke, spend long hours at high altitudes, or are exposed to high levels of carbon monoxide where they work or live also are at risk.
                
For example, working in an underground parking garage or living in a home with a poorly vented fireplace or furnace can raise your risk for secondary polycythemia.
                
Rarely, tumors can make and release EPO, or certain blood problems can cause the body to make more EPO.
                
Sometimes doctors can cure secondary polycythemiait depends on whether the underlying cause can be stopped, controlled, or cured.
Polycythemia vera (PV) develops slowly. The disease may not cause signs or symptoms for years.
                
When signs and symptoms are present, they're the result of the thick blood that occurs with PV. This thickness slows the flow of oxygen-rich blood to all parts of your body. Without enough oxygen, many parts of your body won't work normally.
                
The signs and symptoms of PV include:
                
Headaches, dizziness, and weakness
                
Shortness of breath and problems breathing while lying down
                
Feelings of pressure or fullness on the left side of the abdomen due to an enlarged spleen (an organ in the abdomen)
                
Double or blurred vision and blind spots
                
Itching all over (especially after a warm bath), reddened face, and a burning feeling on your skin (especially your hands and feet)
                
Bleeding from your gums and heavy bleeding from small cuts
                
Unexplained weight loss
                
Fatigue (tiredness)
                
Excessive sweating
                
Very painful swelling in a single joint, usually the big toe (called gouty arthritis)
                
In rare cases, people who have PV may have pain in their bones.
                
Polycythemia Vera Complications
                
If you have PV, the thickness of your blood and the slowed blood flow can cause serious health problems.
                
Blood clots are the most serious complication of PV. Blood clots can cause a heart attack or stroke. They also can cause your liver and spleen to enlarge. Blood clots in the liver and spleen can cause sudden, intense pain.
                
Slowed blood flow also prevents enough oxygen-rich blood from reaching your organs. This can lead to angina (chest pain or discomfort) and heart failure. The high levels of red blood cells that PV causes can lead to stomach ulcers, gout, or kidney stones.
                
Some people who have PV may develop myelofibrosis (MY-e-lo-fi-BRO-sis). This is a condition in which your bone marrow is replaced with scar tissue. Abnormal bone marrow cells may begin to grow out of control.
                
This abnormal growth can lead to acute myelogenous (my-eh-LOJ-eh-nus) leukemia (AML), a cancer of the blood and bone marrow. This disease can worsen very quickly.