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PORPHYRIA CUTANEA TARDA

Porphyria cutanea tarda  is the most common and readily treated form of porphyria and is caused by a deficiency of uroporphyrinogen decarboxylase in the liver. It is most common in men but has become more frequent in women in association with alcohol.

Both acquired and inherited factors can play causative roles in porphyria cutanea tarda. Individual cases can be classified as "sporadic" (type I) or "familial" (type II). The majority of cases are type I, in which uroporphyrinogen decarboxylase mutations are not found and the enzyme is deficient in the liver but not in erythrocytes and other tissues. The amount of hepatic uroporphyrinogen decarboxylase protein.

Most patients with porphyria cutanea tarda have a history of moderate or heavy alcohol intake. The disease may develop in men treated with estrogens for prostate cancer and in women taking oral contraceptives or replacement estrogens. Cutaneous photosensitivity is the major clinical feature. Vesicles and bullae develop on the face, dorsum of the hands and feet, forearms.

Liver histopathology is not usually diagnostic of alcoholic liver disease. Cirrhosis and hepatocellular carcinomas are most common in older patients and at autopsy. In some locations as many as 80% of patients with porphyria cutanea tarda are PCT sometimes occurs in patients with advanced renal disease. Skin lesions may be more severe and plasma porphyrin levels much higher in this setting because urinary excretion of porphyrins is not possible and they are poorly dialyzed.

Very rarely, hepatic tumors themselves contain and presumably produce excess porphyrins. Some of these cases have resembled PCT.

Skin lesions in PCT, VP, and HCP are indistinguishable clinically and histologically. It is important to differentiate these conditions by laboratory testing before starting therapy. A predominance of uroporphyrin and heptacarboxyl porphyrin in urine.

TREATMENT.

A course of phlebotomies is the preferred treatment and almost always produces a remission. Patients are also advised to discontinue the use of alcohol, estrogens, iron supplements, or other contributing factors. Because iron stores in PCT are seldom markedly increased and may be normal, removal of only 5 to 6 U of blood at 1- to 2-week intervals is usually sufficient.

A course of low-dose chloroquine, 125 mg twice weekly, or hydroxychloroquine, 100 mg twice weekly for several months, is usually effective when repeated phlebotomies are contraindicated. The mechanism of their effects in PCT has not been established. One hypothesis is that chloroquine forms complexes with porphyrins and promotes their removal from the liver.

Therapy is more difficult when PCT occurs with advanced renal disease because phlebotomy is usually contraindicated by anemia (usually because of erythropoietin deficiency). Recent studies indicate that genetic recombinant erythropoietin.