Studies of laminin and type IV collagen in blisters of porphyria cutanea tarda and drug-induced pseudoporphyria.

Abstract

Blisters from five patients with porphyria cutanea tarda and two patients with drug-induced pseudoporphyria were examined by direct immunofluorescence and by immunofluorescence mapping with antibodies against laminin and type IV collagen to determine the level of subepidermal separation. Primary screening by direct immunofluorescence revealed the characteristic immune deposits in the vessel walls of the upper dermal plexus in all cases and at the dermoepidermal junction in five of seven cases. Type IV collagen and laminin were reactive in six and five cases, respectively, and appeared in the floor of the bulla. The findings were identical in porphyria and pseudoporphyria. In one case in which the bullous pemphigoid antigen could be detected, it appeared in the epidermal roof of the bulla. These findings indicate that the split in porphyria and pseudoporphyria occurs in the lamina lucida. We propose that a multistep mechanism involved in the induction of blisters may be similar in porphyria and pseudoporphyria.