The Porphyrias

Abstract

The porphyrias are uncommon disorders caused by deficiencies in the activities of enzymes of the heme biosynthetic pathway. The enzymatic defects that cause porphyrias are inherited, with the exception of porphyria cutanea tarda, which is primarily acquired. In all porphyrias, there is significant interplay between genetic traits and acquired or environmental factors in the expression of clinical symptoms. This review discusses the classification, pathophysiology, and clinical presentations of the porphyrias. These include those associated with neurovisceral attacks (acute intermittent porphyria, variegate porphyria, hereditary coproporphyria, and δ-aminolevulinic acid dehydratase [alad] deficiency porphyria) and the porphyrias associated with cutaneous photosensitivity (porphyria cutanea tarda, hepatoerythropoietic porphyria, erythropoietic protoporphyria, and congenital erythropoietic porphyria). Specific emphasis on the epidemiology, molecular defects and pathophysiology, clinical features, diagnosis, and treatment are discussed for each of these disorders. A table lists the safe and unsafe drugs for patients with porphyrias. Figures illustrate the genetic pathways of the disorders and the activities of enzymes of the heme biosynthetic pathway. This review contains 2 highly rendered figures, 1 table, and 96 references.