By Gary M. White, MD
Blisters and fragility on the back of the hands.
Porphyria cutanea tarda is a blistering disease, most common on the back of the hands caused by sun exposure and build up in the blood of porphyrins. Both an inherited (AD) and an acquired type have been described. For both types, uroporphyrinogen decarboxylase functional activity is low, and a history of exposure to alcohol, estrogens (e.g. oral contraceptives for women or estrogen for prostate cancer in men) or a liver toxic agent may be found. In one study, Hepatitis C virus antibodies were found in 79% of patients with acquired PCT and in none with familial PCT. The connection between PCT and Hepatitis C varies tremendously by geographic location. For example, the presence of HC in PCT patients has been reported as follows: Indiana (in the US) 94%, Southern Europe 65%, Australia/New Zealand 20%, Northern Europe 17% [JAAD 1999;41;31]. Hepatocellular carcinoma may cause PCT as a paraneoplastic manifestation [BJD 1997;136;129]. Removing the carcinoma causes resolution of the symptoms. See also induration in PCT.
Vesicles, milia, erosions and fragile skin occur symmetrically on the dorsa of the hands in porphyria cutanea tarda. Look for hypertrichosis along the forehead. In rare cases, usually when the disease goes for a long time untreated, indurated, sclerodermoid plaques may develop on the trunk. In one case, a photodistributed lichenoid dermatitis was associated [BJD 1999;141;123]. The hematocrit is often elevated.
Diagnosis is made by measuring urinary porphyrins and excluding VP through measurement of fecal porphyrins. PCT may develop in the setting of renal failure and dialysis. Finally, a bullous dermatosis mimicking PCT (pseudoporphyria) but without elevated porphyrin levels may also occur in dialysis patients. This type may be related to various drugs (e.g. furosemide, nalidixic acid and tetracycline).
Sun protection is key. The action spectrum appears to be primarily in the UVA range so sunscreens with UVA blockage are mandatory. Those often include the metal-containing sunscreens. Some have theorized that even the visible spectrum plays a role. The damage to the skin occurs over months and thus repair will occur over a similar timeframe.
Hydroxychloroquine 100 mg po twice weekly is an excellent treatment option and may be first line [Clin Gastroenterol Hepatol 2012;Dec 10;1402]. It should be avoided in patients with hepatic or renal dysfunction. Time to remission is about 6 months.
Phlebotomy has been the primary treatment for years, but is expensive, somewhat inconvenient and has the risk of inducing anemia or syncope. A unit of blood is removed every 2-4 weeks to decrease the hematocrit. The CBC should be followed and phlebotomy withheld if the hemoglobin level is < 10 g/dL or the hematocrit level < 33.
For the PCT of renal failure and dialysis, erythropoietin and phlebotomy, deferoxiamine or renal transplantation have been used.
PCT in a patient on peritoneal dialysis.
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