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Porphyria cutanea tarda is the most common porphyria and causes blistering and fragility of skin exposed to sunlight.
Porphyria cutanea tarda occurs throughout the world. As far as is known, one form of this porphyria is the only one that can occur in people who do not have an inherited deficiency of an enzyme involved in heme production.
Porphyria cutanea tarda results from underactivity of the enzyme uroporphyrinogen decarboxylase, which leads to accumulation of porphyrins in the liver. Skin damage occurs because of overproduction of porphyrins in the liver being transported by the blood to the skin.
Porphyria cutanea tarda has several common precipitating factors. These factors include excess iron in the liver, moderate or heavy alcohol use, taking estrogens, and infection with hepatitis C virus. Infection with the human immunodeficiency virus (HIV) is a less common precipitating factor. These factors are thought to interact with iron and oxygen in the liver and thereby inhibit or damage the enzyme uroporphyrinogen decarboxylase.
In about 80% of people with porphyria cutanea tarda, the disorder does not appear to be hereditary and is called sporadic. In the remaining 20%, the disorder is hereditary and is called familial.
Symptoms and Diagnosis
People with porphyria cutanea tarda experience chronic, recurring blisters of various sizes on sun-exposed areas such as the arms, face, and especially the backs of the hands. Crusting and scarring follow the blisters and take a long time to heal. The skin, especially on the hands, is also sensitive to minor injury. Hair growth on the face and other sun-exposed areas may increase. Liver damage usually occurs, and cirrhosis and even liver cancer may eventually develop.
To diagnose porphyria cutanea tarda, doctors test urine and stool for unusually high levels of porphyrins. The specific porphyrins that are increased provide a pattern that allows doctors to distinguish porphyria cutanea tarda from other porphyrias.
Treatment
Porphyria cutanea tarda is the most readily treated porphyria. Avoiding alcohol and other precipitating factors is beneficial.
A procedure called phlebotomy, in which a pint (almost half a liter) of blood is removed, is the most widely recommended treatment. With phlebotomy, the excess iron is gradually removed, the activity of uroporphyrinogen decarboxylase in the liver returns toward normal, and porphyrin levels in the liver and blood fall gradually. The skin symptoms resolve, and the skin eventually returns to normal. Phlebotomy sessions are stopped when people become slightly iron deficient. Anemia may develop if too many phlebotomy sessions are done or if sessions are done too frequently.
Very low doses of chloroquine or hydroxychloroquine are also effective in treating porphyria cutanea tarda. These drugs remove excess porphyrins from the liver. However, doses that are too high cause porphyrins to be removed too rapidly, resulting in a temporary worsening of the disorder and damage to the liver.
Combining phlebotomy and chloroquine treatments accelerates improvement.
For women taking estrogen, doctors stop the estrogen therapy (because it is a precipitating factor of the porphyria) until phlebotomy has been completed and porphyrin levels are normal. The estrogen is then restarted and seldom causes a recurrence of the porphyria.
Last full review/revision August 2008 by Stig Thunell, MD, PhD
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