Skin morphology in porphyria cutanea tarda does not improve despite clinical remission

Five patients with porphyria cutanea tarda (PCT) were treated with a prolonged, low-dose chloroquine regimen (250 mg twice weekly). Their skin symptoms disappeared, and the abnormal urinary porphyrin excretion normalized during treatment periods ranging from 6 to 17 (mean 11.8) months. The morphology of the skin was studied by light and electron microscopy methods before treatment, at the onset of remission, and 6-12 months later. In samples taken during remission, the PAS-positive thickening of the superficial dermal vessels was comparable to that before treatment. In electron microscopy, the vessels showed thickening because of reduplication of the basal lamina and perivascular deposition of amorphous material; no consistent changes were found during remission. The results show that the histopathological changes of the skin in PCT are of chronic nature, and are probably irreversible.