A type of porphyria in which affected individuals are sensitive to sunlight. Exposed skin shows abnormalities that range from slight fragility of the skin to persistent scarring and disfiguration. Due to fragility of the skin, minor trauma may induce blister formation. Areas of increased and decreased pigment content may be noted on the skin. Blistering of light exposed skin and increased hair growth are also characteristic.
PCT is caused by a deficiency of the uroporphyrinogen decarboxylase (URO-D) enzyme in the liver. The disorder can be acquired or can be caused by an inherited gene mutation in the UROD gene. The inherited form of PCT is also called familial PCT and follows autosomal dominant inheritance. Many individuals with a UROD gene mutation never experience symptoms of the disease.
PCT becomes active and causes symptoms when triggered by an environmental factor that affects liver cells (hepatocytes). These environmental factors include alcohol, estrogens, hepatitis C, and human immunodeficiency viruses (HIV). Individuals who have disorders that lead to excess iron in tissues such as hemochromatosis also have an increased risk of developing PCT. It is usually necessary for an environmental trigger to be present to cause symptoms of either the acquired or inherited type of PCT.