Porphyria cutanea tarda is the most common type of porphyria. In about 80% of people with porphyria cutanea tarda, the disorder does not appear to be hereditary and is called sporadic. Porphyria may be inherited or acquired during life. There are at least seven types of porphyria. Each is due to a slightly different enzyme deficiency and tends to show a different pattern of symptoms and problems.
The porphyrias may be inherited as either autosomal dominant (caused by inheriting 1 abnormal copy of the gene) or autosomal recessive (requires inheritance of 2 abnormal genes) traits, depending on which type of porphyria is involved.
PCT is caused by a deficiency of the uroporphyrinogen decarboxylase (URO-D) enzyme in the liver. It is usually necessary for an environmental trigger to be present to cause symptoms of either the acquired or inherited type of PCT.
Urine may become red or brown following an attack. Exposure to sunlight can cause reddening, pain, sensations of heat, blistering, and edema in the skin. These lesions heal slowly, often with scarring or pigment changes and may be disfiguring. Some people develop mottled brown patches around the eyes and increased facial hair. Occasionally the skin becomes hardened (sclerodermoid) on the neck, face or chest. There may be small areas of permanent baldness (alopecia) or ulcers.
The treatment of choice for PCT is removal of iron by therapeutic phlebotomy. Successful antiviral therapy of chronic hepatitis C may also produce remission, as may low-dose therapy with anti-malarial drugs such as chloroquine.
Phlebotomy reduces the amount of iron in the patient's system, and since iron inhibits the deficient enzyme this is very helpful. Porphyrin levels in the liver and plasma fall and the skin will become normal. It is usually only necessary to perform this treatment five or six times. One can also take very low doses - even lower than normal clinical dosages - of chloroquine or hydroxychloroquine, which remove excess porphyrins from the liver. The patient should also avoid alchohol.
Therapeutic measures for porphyria cutanea tarda include avoidance of exacerbating factors, especially ultraviolet light, ethanol, and certain medications. Phlebotomy or chloroquine therapy is reserved for patients in whom conservative measures fail.
Usual dosages of these drugs should not be used because they can cause transient but sometimes severe liver damage and worsening of photosensitivity in PCT patients. Recurrences can be treated in the same manner. But PCT usually does not recur after treatment. It is not necessary to continue phlebotomies after a remission has been achieved.