Porphyria cutanea tarda. Don't forget to look at the urine.

Diagnosis of porphyria cutanea tarda is usually fairly straightforward because of the characteristic clinical findings. Blisters and erosions develop acutely on sun-exposed skin, sometimes accompanied by hypertrichosis, abnormal pigmentation, and milia formation. Iron stores are usually elevated, and liver transaminases and blood glucose levels are often above normal as well. Gross examination of the urine can provide a valuable clue, since urine of porphyria cutanea tarda patients is red to brown in natural light and pink to red in fluorescent light. Biopsy of a bullous lesion is useful to rule out other diseases. Confirmation of porphyria cutanea tarda requires measurement of porphyrin levels in a 24-hour urine collection. Once the diagnosis is confirmed, it appears reasonable to screen all patients with porphyria cutanea tarda for hepatitis C and possibly B, but especially those less than 30 years old who have extremely high liver transaminase levels. Therapeutic measures for porphyria cutanea tarda include avoidance of exacerbating factors, especially ultraviolet light, ethanol, and certain medications. Phlebotomy or chloroquine therapy is reserved for patients in whom conservative measures fail.