Finasteride-Induced Pseudoporphyria

The article reports a case of a 56-year-old man who presented with asymptomatic tense blisters on his hands and feet of 10 days' duration. The patient had no significant medical history and denied a family history of photosensitivity and bullous diseases. His only medication was finasteride, 1 mg/d, which he began taking 7 months prior to the onset of blisters. Results of serum porphyrin assays and 24-hour urine porphyrin analyses were negative, with the exception of a coproporphyrin level of 2.0 µg/L on serum analysis (normal limit, ≤0.8 µg/L). The results of additional laboratory studies, notably creatinine, blood urea nitrogen, liver function tests, and ferritin levels, were within normal limits. Biopsy specimens analyzed by both hematoxylin-eosin staining and direct immunofluorescence showed cell-poor, subepidermal, vesicular dermatitis consistent with porphyria cutanea tarda (PCT) or pseudoporphyria. A diagnosis of finasteride-induced pseudoporphyria was made, and treatment with the drug was discontinued.