Atrichia with papular lesions (APL) is a rare genetic disorder characterized by the absence of scalp hair (atrichia) and the presence of small, raised bumps (papules) on the skin. It is caused by mutations in the FOXL2 gene. Symptoms may include t...

Atrioventricular defect-blepharophimosis-radial and anal defect syndrome (AVBRAD) is a rare genetic disorder characterized by a combination of heart defects, blepharophimosis (a condition in which the eyelids are abnormally narrow), radial and ana...

Atrioventricular septal defect (AVSD) is a congenital heart defect in which there is an abnormal connection between the two upper chambers of the heart (the atria) and the two lower chambers of the heart (the ventricles). This defect can cause blo...

Atrophic lichen planus is a rare form of lichen planus, a chronic inflammatory skin condition. It is characterized by thin, atrophic (thinning) patches of skin that are usually lighter in color than the surrounding skin. The patches may be itchy o...

Atrophoderma vermiculata is a rare skin condition characterized by small, pitted, and slightly raised patches on the skin. It is most commonly found on the face, neck, and upper chest, and is thought to be caused by a combination of genetic and en...

Attention deficit hyperactivity disorder (ADHD) is a mental-health condition that has characteristics of difficulty concentrating, controlling impulses, and/or excessive activity. Though there is no particular cause of ADHD, there a...

Attention deficit hyperactivity disorder is a behavioral condition characterized by distractibility, impulsivity, and/or hyperactivity. Although there is no single cause for ADHD, there are a number of biological and social factors ...

Attention deficit hyperactivity disorder (ADHD) is one of the most common chronic disorders affecting school-age children. Current research indicates prevalence rates of 3% to 5% with males being diagnosed with this disorder two and a half times m...

Attenuated Chediak-Higashi syndrome (A-CHS) is a rare, inherited disorder that affects the immune system. It is caused by a mutation in the CHS1 gene, which is responsible for producing a protein that helps the body fight off infections. People wi...

ATTRV122I amyloidosis is a rare, inherited form of amyloidosis caused by a mutation in the transthyretin (TTR) gene. It is characterized by the buildup of abnormal proteins in the body's organs and tissues, leading to organ damage and other seriou...

ATTRV30M amyloidosis is a rare, progressive, and fatal genetic disorder caused by a mutation in the transthyretin (TTR) gene. It is characterized by the buildup of abnormal proteins called amyloid in the body's organs and tissues, which can lead t...

Atypical autism is a form of autism that is characterized by milder symptoms than those seen in other forms of autism. People with atypical autism may have difficulty with social interaction, communication, and repetitive behaviors, but these diff...

Atypical chronic myeloid leukemia (aCML) is a rare form of chronic myeloid leukemia (CML) that is characterized by an abnormal number of white blood cells, an abnormal number of immature cells, and an abnormal number of blasts in the bone marrow. ...

Atypical coarctation of the aorta is a rare congenital heart defect in which the aorta is narrowed in an abnormal location. It is usually located in the descending aorta, just beyond the left subclavian artery. This condition can cause a decrease ...

Atypical dentin dysplasia due to SMOC2 deficiency is a rare genetic disorder that affects the development of teeth. It is caused by mutations in the SMOC2 gene, which is responsible for producing a protein that is essential for the formation of de...

Atypical Fanconi syndrome-neonatal hyperinsulinism syndrome is a rare genetic disorder that affects the body’s ability to regulate insulin levels. It is characterized by an abnormally high level of insulin in the blood, which can lead to a varie...

Atypical Gaucher disease due to saposin C deficiency is a rare, inherited disorder caused by a mutation in the GBA gene. This mutation results in a deficiency of the enzyme saposin C, which is responsible for breaking down certain fats in the body...