Porphyria Cutanea Tarda - Causes, Symptoms and Treatment

Definition

The Porphyria cutanea tarda is a term used for group of diseases in which there is a defect somewhere in the complex chain of chemical steps that are required for the synthesis of the molecule known as haem. Familial PCT most often reflects the presence of 1 mutation at the uroporphyrinogen decarboxylase locus. A rare familial type with 2 such mutations has been termed hepatoerythropoietic 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. Several common factors are associated with porphyria cutanea tarda; these include excess iron in body tissues, moderate or heavy alcohol use, taking estrogens such as PREMARIN, infection with hepatitis C virus, and possibly smoking. Infection with the human immunodeficiency virus is a less common precipitating factor.

Causes

1. Porphyria cutanea tarda is due to a defective enzyme in the liver i.e. uroporphyrinogen decarboxylase. This is involved in synthesis of the red pigment in blood cells which is called haem.
2. Each step is controlled by a particular protein enzyme. But in Porphyria cutanea tarda there is a deficiency of these enzymes and so the process is blocked and porphyrins accumulate to toxic levels in the body.
3. It generally begins in mid-adult life after exposure to certain chemicals that increase the production of porphyrins in the liver. These substances may include alcohol, oestrogen or polychlorinated aromatic hydrocarbons etc.
4. Other causes are due to excessive intake, viral infections or chronic blood disorders such as thalassaemia.

Symptoms

1. You may have red or brown urine.
2. Affected people get blisters on areas of the skin which are exposed to the sun. It also makes the skin sensitive to minor trauma.
3. Crusting and scarring may also occur and will take a long time to heal.
4. Porphyria cutanea tarda can also cause liver damage, including liver cancer and cirrhosis of the liver.
5. There may occur skin swelling on exposure to sunlight.
6. Porphyria cutanea tarda may lead to Photo dermatitis.
7. Constipation may occur
8. Other symptoms are vomiting, pain in limbs, personality change, numbness or tingling, muscle pain, muscle weakness or paralysis.

Treatment

1. Sunlight avoidance is the main defense for photosensitivity until clinical remission can be induced.
2. Estrogen use should be discontinued unless its need outweighs its adverse effects on porphyrin metabolism.
3. Therapeutic phlebotomy reduces iron stores, which improves heme synthesis disturbed by ferroinhibition of uroporphyrinogen decarboxylase. The goal of therapy is to reduce serum ferritin levels to the lower limit of the reference range.
4. Alcohol should be strictly avoided.
5. Venisection, the removal of 500 ml of blood q 2 weeks, gradually results in remission.
6. Oral cloroquine, starting at very low doses to avoid an acute exacerbation of symptoms, can also be highly effective.
7. For patients with pseudoporphyria secondary to dialysis, erythropoietin in combination with venisection may be helpful.