Phosphoglycerate dehydrogenase deficiency is a condition characterized by an unusually small head size (microcephaly); impaired development of physical reactions, movements, and speech (psychomotor retardation); and recurrent seizures (epilepsy). Dif READ MORE

Phosphoglycerate kinase deficiency is a genetic disorder that affects the body's ability to break down the simple sugar glucose, which is the primary energy source for most cells. Researchers have described two major forms of the condition. The most READ MORE

Phosphoglycerate mutase deficiency is a disorder that primarily affects muscles used for movement (skeletal muscles). Beginning in childhood or adolescence, affected individuals experience muscle aches or cramping following strenuous physical activit READ MORE

Phosphoribosylpyrophosphate synthetase superactivity (PRS superactivity) is characterized by the overproduction and accumulation of uric acid (a waste product of normal chemical processes) in the blood and urine. The overproduction of uric acid can l READ MORE

Piebaldism is a condition characterized by the absence of cells called melanocytes in certain areas of the skin and hair. Melanocytes produce the pigment melanin, which contributes to hair, eye, and skin color. The absence of melanocytes leads to pat READ MORE

Pilomatricoma, also known as pilomatrixoma, is a type of noncancerous (benign) skin tumor associated with hair follicles. Hair follicles are specialized structures in the skin where hair growth occurs. Pilomatricomas occur most often on the head or n READ MORE

Pitt-Hopkins syndrome is a condition characterized by intellectual disability and developmental delay, breathing problems, recurrent seizures (epilepsy), and distinctive facial features. People with Pitt-Hopkins syndrome have moderate to severe intel READ MORE

Platyspondylic dysplasia, Torrance type is a severe disorder of bone growth. Infants with this condition have very short arms and legs, severely flattened bones of the spine (platyspondyly), and unusually short fingers and toes (brachydactyly). Affec READ MORE

PLCG2-associated antibody deficiency and immune dysregulation (PLAID) is an immune system disorder characterized by an allergic reaction to cold temperatures. Other immune system problems can also occur. The hallmark feature of PLAID is the developme READ MORE

PMM2 -congenital disorder of glycosylation ( PMM2 -CDG, also known as congenital disorder of glycosylation type Ia) is an inherited condition that affects many parts of the body. The type and severity of problems associated with PMM2 -CDG vary widely READ MORE

Poikiloderma with neutropenia (PN) is a disorder that mainly affects the skin and the immune system. This condition begins with a bumpy rash that usually appears between the ages of 6 and 12 months, gradually spreading from the arms and legs to the t READ MORE

Pol III-related leukodystrophy is a disorder that affects the nervous system and other parts of the body. Leukodystrophies are conditions that involve abnormalities of the nervous system's white matter, which consists of nerve cells (neurons) covered READ MORE