Genetic aspects of porphyria cutanea tarda.

Porphyria cutanea tarda (PCT) is caused by disruption of heme biosynthesis at the step catalyzed by uroporphyrinogen decarboxylase. The patients present with photosensitive cutaneous lesions, hepatic pathology (including elevated porphyrin levels), and increased excretion of porphyrins. Therapy consists of removing the exacerbating factors of PCT (reduced sunlight exposure, abstinence from alcohol use, decreased estrogen exposure, and treatment for viral infections), decreasing body iron stores (by therapeutic phlebotomy or by the use of the new orally active iron chelators), and, in some instances, the use of low-dose antimalarials. Recent advances in genetics and genomics have allowed DNA testing for porphyria cutanea tarda and are likely to be instrumental in developing improved, gene-based treatments and in finding genetic loci (in addition to uroporphyrinogen decarboxylase) involved in the clinical expression of this disease.