The Porphyrias

The porphyrias are metabolic diseases caused by altered activities of enzymes in the heme biosynthetic pathway. Signs and symptoms of porphyria result from overproduction and accumulation of pathway intermediates. Recognizing the different types of porphyrias can be challenging due to similarities in presentation but etiology, pathogenesis, methods for diagnosis and treatment for each are distinct. In this overview of the porphyrias, we describe the eight enzymes in the heme biosynthetic pathway associated with each type of porphyria. We classify these diseases by their erythropoietic or hepatic origin and their cutaneous or neurovisceral manifestations. The etiology and pathophysiology specific to the type of porphyria is linked to the specific enzyme in the heme biosynthetic pathway. Emphasis is placed on specific clinical features, relevant diagnostic evaluation and appropriate therapy for each porphyria pertinent to treating physicians and clinicians.