Pseudoporphyria or porphyria cutanea tarda? Diagnostic and treatment difficulties.

Fig. 1. Erosions on the forehead. Fig. 2. Erosions, milia and scarring on the dorsum of the hand. Sir, Porphyria cutanea tarda (PCT) is a vesiculobullous skin disorder of heme biosynthesis in which there is an enzyme defect of uroporphyrinogen decarboxylase (Uro-D), leading to accumulation of porphyrins mainly in urine but also in stool and plasma. Pseudoporphyria is clinically similar to PCT, but usually lacks the biochemical abnormalities, and is difficult to distinguish clinically and histologically. This case report shows how challenging differential diagnosis between PCT and pseudoporphyria can be, especially in the setting of renal failure and haemodialysis, and it emphasizes the treatment difficulties with renal failure patients and pseudoporphyria. A qualitative and quantitative examination of urine, plasma and stool porphyrins and Uro-D enzyme test in red blood cells is required.