Porphyria cutanea tarda and chronic renal failure.

Bullous dermatosis developed in a patient with renal failure who was on hemodialysis. The results of standard tests for porphyria cutanea tarda--quantitation of urinary and fecal porphyrins by fluorometric assay--were within normal limits or were nondiagnostic. Assay of plasma using high-pressure liquid chromatography, however, revealed that this patient had a porphyrin profile consistent with porphyria cutanea tarda. A porphyria-like bullous eruption may occur in patients with chronic renal failure; however, in only a few cases have laboratory studies confirmed the diagnosis of porphyria cutanea tarda. Our experience suggests that, in patients with renal failure, a plasma assay may be more reliable than tests of the urine and feces in establishing a diagnosis in those patients who actually have disorders of porphyrin metabolism. We also report the results of assay of erythrocyte uroporphyrinogen decarboxylase activity and fecal isocoproporphyrin.