We performed a histopathological investigation of the bullous lesions in 3 cases of porphyria cutanea tarda. All cases showed subepidermal bullae by light microscopy. PAS positive materials were present on the roof of the bullae and partially present on their bases. Electronmicroscopically, the basal lamina was clearly recognized on the base. From these results, we suggest that the blister in porphyria cutanea tarda occurs initially within the junctional zone; this initial bulla may quickly change into a dermolytic bulla with additional stimulation.

Fecal, urinary and erythrocyte porphyrin analyses using the solvent extraction method were performed in 26 patients with porphyria cutanea tarda (PCT) and 144 normal controls. The levels of fecal uroporphyrin (UP) and coproporphyrin (CP) were markedly increased in the PCT group, especially in comparison with the protoporphyrin (PP) level. The values of the UP/PP and CP/PP ratios in the feces were also elevated over those in the control group. It appears that fecal porphyrin excretion is basically similar to urinary porphyrin excretion in PCT. The analysis of fecal porphyrins and the observation of fecal UP/PP and CP/PP ratios may be helpful in the biochemical diagnosis of PCT. In particular, the elevation of CP/PP ratio is characteristic of PCT.

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