Porphyria cutanea tarda (PCT) is a form of porphyria that primarily affects the skin. People affected by this condition generally experience "photosensitivity," which causes painful, blistering lesions to develop on sun-exposed areas of the skin (i.e. the hands and face). Skin in these areas may also be particularly fragile with blistering and/or peeling after minor trauma. In some cases, increased hair growth as well as darkening and thickening of the affected skin may occur. Liver abnormalities may develop in some people with the condition and PCT, in general, is associated with an increased risk of liver cirrhosis and liver cancer. In most cases, PCT is a complex or multifactorial condition that is likely associated with the effects of multiple genes in combination with lifestyle and environmental factors. For example, factors such as excess iron, alcohol, estrogens, smoking, chronic hepatitis C, HIV and genetic changes in the HFE gene (which is associated with the disease hemochromatosis) can all contribute to the development of PCT. Less commonly, PCT can run in families (called familial PCT). Familial PCT is caused by changes in the UROD gene and is inherited in an autosomal dominant manner.