Porphyria cutanea tarda is the most common type of porphyria. The disorder results from low levels of the enzyme responsible for the fifth step in heme production. Heme is a vital molecule for all of the body's organs. It is a component of hemoglobin, the molecule that carries oxygen in the blood. Porphyria cutanea tarda is a subtype of porphyria. When signs and symptoms occur, they usually begin in adulthood and result from the skin becoming overly sensitive to sunlight. Areas of skin exposed to the sun develop severe blistering, scarring, changes in pigmentation, and increased hair growth. Exposed skin becomes fragile and is easily damaged. People with porphyria cutanea tarda also have increased iron levels in the liver. They face a higher risk of developing abnormal liver function and liver cancer. The signs and symptoms of this condition are triggered by nongenetic factors such as alcohol abuse, excess iron, certain hormones, and viral infections.