Aarskog syndrome Facial-digital-genital syndrome Causes, incidence, and risk factors: Aarskog syndrome is a genetic disorder that is linked to the X chromosome. It affects mainly males, but females may have a milder form. The condition is caused by changes (mutations) in a gene called "faciogenital dysplasia" ( FGD1 ).
Aase syndrome Aase-Smith syndrome; Hypoplastic anemia/Triphalangeal thumb syndrome Causes, incidence, and risk factors: Most cases of Aase syndrome occur without a known reason and are not passed down through families (inherited). However, some cases have been shown to be inherited. The anemia in Aase syndrome is caused by poor development of the bone marrow, which is where blood cells are formed.
Abdominal aortic aneurysm Aneurysm - aortic; AAA Causes, incidence, and risk factors: The exact cause is unknown, but risk factors for developing an abdominal aortic aneurysm include: Emphysema Genetic factors High blood pressure High cholesterol Male gender Obesity Smoking An abdominal aortic aneurysm can develop in anyone, but is most often seen in males over age 60 who have one or more risk factors.
ABO incompatibility A, B, and O are the three major blood types. The types are based on small substances (molecules) on the surface of the blood cells. When people who have one blood type receive blood from someone with a different blood type, it may cause their immune system to react. This is called ABO incompatibility. Causes, incidence, and risk factors: The different blood types are: Type A Type B Type AB Type O People who have one blood type may form proteins (antibodies) that cause their immune system to react against one or more of the other blood types.
Abscess An abscess is a collection of pus in any part of the body that, in most cases, causes swelling and inflammation around it. Causes, incidence, and risk factors: Abscesses occur when an area of tissue becomes infected and the body's immune system tries to fight it. White blood cells move through the walls of the blood vessels into the area of the infection and collect in the damaged tissue. During this process, pus forms. Pus is the buildup of fluid, living and dead white blood cells, dead tissue, and bacteria or other foreign substances.
Absent pulmonary valve Absent pulmonary valve syndrome; Congenital absence of the pulmonary valve; Pulmonary valve agenesis Causes, incidence, and risk factors: Absent pulmonary valve occurs when the pulmonary valve doesn't form or develop properly while the baby is in the mother's womb.
Acanthosis nigricans Acanthosis nigricans is a skin disorder in which there is darker, thick, velvety skin in body folds and creases. Causes, incidence, and risk factors: Acanthosis nigricans can affect otherwise healthy people, or it can be related to medical problems. Some cases are genetically inherited. The condition is most commonly seen among people of African descent, in part because it is easier to see in darker skin. Obesity can lead to acanthosis nigricans, as can some endocrine disorders.
Achalasia Esophageal achalasia Causes, incidence, and risk factors: A muscular ring at the point where the esophagus and stomach come together (lower esophageal sphincter) normally relaxes during swallowing. In people with achalasia, this muscle ring does not relax as well. The reason for this problem is damage to the nerves of the esophagus.
Achilles tendinitis Tendinitis of the heel Causes, incidence, and risk factors: There are two large muscles in the calf. These muscles are important for walking. They create the power needed to push off with the foot or go up on the toes.
Achondrogenesis Achondrogenesis is a rare type of growth hormone deficiency in which there is a defect in the development of bone and cartilage. Causes, incidence, and risk factors: Achondrogenesis is inherited, which means it is passed down through families. Some types are known to be recessive, meaning both parents carry the defective gene and the chance for a subsequent child to be affected is about 25%. Symptoms: Very short trunk, arms, legs, and neck Head appears large in relation to the trunk Small lower jaw Narrow chest Signs and tests: X-rays show bone problems associated with the condition.