Pseudoporphyria Cutanea Tarda

In patients with chronic renal failure who are receiving maintenance hemodialysis, an eruption indistinguishable from that of porphyria cutanea tarda may develop on the dorsa of the hands and fingers during the summer months . Rarely, blisters are seen also on the face, and atrophic scarring develops . In a series of 180 patients receiving hemodialysis, 28 (16%) showed this type of eruption . Normal porphyrin levels in urine, stool, and plasma are the rule in hemodialyzed patients developing clinical signs of porphyria cutanea tarda. However, in a few patients receiving hemodialysis for chronic renal failure, a true porphyria cutanea tarda coexists . In such patients, if a certain degree of diuresis persists, urinalysis may not be representative of the porphyria metabolism, and the plasma and fecal porphyrins should always be measured .

Pseudoporphyria cutanea tarda may also occur following the ingestion of certain drugs, such as furosemide, nalidixic acid, tetracycline hydrochloride, and naproxen (135). Because many patients on hemodialysis for renal failure also are receiving furosemide, withdrawal of the drug can determine whether the dialysis or the medication is the cause of the pseudoporphyria, because in drug-induced cases, withdrawal of the drug is curative .

Histopathology. In patients with pseudoporphyria, the histologic picture is indistinguishable from that seen in mild cases of porphyria. The superficial blood vessels show thickened walls, and the PAS-positive basement membrane zone is often thickened as well. Blisters are subepidermal, with festooned dermal papillae. The blisters usually are situated above the PAS-positive basement membrane zone .

immunoglobulins are often observed in vessel walls and at the dermal-epidermal junction. Complement is also occasionally present .