Absent radius-anogenital anomalies syndrome is a rare genetic disorder characterized by the absence of the radius bone in the forearm, as well as malformations of the genitals and urinary tract. Other features of the disorder may include short sta...

Absent thumb-short stature-immunodeficiency syndrome (ATSIS) is a rare genetic disorder characterized by the absence of the thumb, short stature, and immunodeficiency. It is caused by a mutation in the gene encoding the transcription factor FOXP2....

Absent tibia-polydactyly-arachnoid cyst syndrome is a rare genetic disorder characterized by the absence of the tibia bone in the lower leg, extra fingers or toes (polydactyly), and the presence of an arachnoid cyst in the brain. It is caused by a...

Acanthocheilonemiasis is a rare parasitic infection caused by the nematode Acanthocheilonema perstans. It is spread by the bite of certain species of mosquitoes and is most commonly found in tropical and subtropical regions. Symptoms of the infect...

Neuroacanthocytosis is a general term for a group of rare progressive disorders characterized by the association of misshapen, spiny red blood cells (acanthocytosis) and neurological abnormalities, especially movement disorders. Chorea, which is c...

Acanthokeratolytic verrucous nevus is a rare skin disorder characterized by the presence of wart-like lesions on the skin. These lesions are usually found on the face, neck, and upper trunk and are composed of thickened, scaly skin. They may be pr...

Epidermolysis bullosa (EB) is a genetic skin disorder characterized clinically by blister formation from mechanical trauma. There are four main types with additional sub-types identified. There is a spectrum of severity, and within each type, one ...

Epidermolysis bullosa (EB) is a genetic skin disorder characterized clinically by blister formation from mechanical trauma. There are four main types with additional sub-types identified. There is a spectrum of severity, and within each type, one ...

Acanthosis nigricans is a skin condition characterized by dark, velvety patches of skin that typically appear in body folds and creases, such as the neck, armpits, and groin. It is most commonly associated with insulin resistance and obesity, but ...

Acanthosis nigricans is a skin condition characterized by areas of dark, velvety discoloration in body folds and creases. The affected skin can become thickened. Most often, acanthosis nigricans affects your armpits, groin and neck. The sk...

Acanthosis nigricans-insulin resistance-muscle cramps-acral enlargement syndrome is not a recognized medical condition. Acanthosis nigricans is a skin condition characterized by dark, velvety patches on the skin, usually in the armpits, neck, and ...

Seborrheic Keratosis is a skin disorder usually characterized by discolored lesions that appear to be "stuck on" the skin surface. Warts may appear and skin is often oily or greasy. These skin lesions are sometimes mistaken for cancerous growths a...

Acatalasemia is a rare genetic disorder in which the body is unable to produce the enzyme catalase. This enzyme is responsible for breaking down hydrogen peroxide, a byproduct of metabolism, into oxygen and water. Without catalase, hydrogen peroxi...

Accessory mitral valve tissue (AMVT) is a rare congenital heart defect in which an extra piece of tissue is present in the heart, usually near the mitral valve. This extra tissue can interfere with the normal flow of blood through the heart, leadi...

Accessory pancreas is a rare congenital anomaly in which an additional, small pancreas is present in the abdomen. It is usually located near the duodenum, the first part of the small intestine. Accessory pancreas is usually asymptomatic and is oft...

Accessory tricuspid valve tissue is an abnormal tissue that is found in the heart. It is located in the right atrium, near the tricuspid valve. This tissue is usually made up of fibrous tissue and can cause obstruction of the tricuspid valve, lead...