Porphyrias are rare diseases, and most clinicians will see only a few cases during their professional lives. Each of the seven types is caused by partial deficiency of a different enzyme in the heme biosynthesis pathway (1). Disease-specific mutations in the genes encoding these enzymes have been identified in all of the inherited porphyrias (2). The current repertoire of investigations for porphyria includes measurement of metabolites (heme precursors) that accumulate secondary to the enzyme deficiencies as well as enzyme assays and DNA analyses. Four porphyrias can present with life-threatening acute neurovisceral attacks: [delta]-aminolevulinic acid dehydratase deficiency porphyria, acute intermittent porphyria (AIP), variegate porphyria (VP), and hereditary coproporphyria (HCP) (1). Attacks are often provoked by drugs, endocrine factors, alcohol, fasting, infection, or stress. In VP and HCP, skin lesions, typically erosions and bullae in sun-exposed areas, may accompany an acute attack or, particularly in VP, be the sole presenting symptom. [delta]-Aminolevulinic acid dehydratase deficiency porphyria is a very rare, autosomal recessive disease (3) and will not be discussed here. AIP, VP, and HCP are autosomal dominant disorders that show incomplete penetrance with symptoms developing in only ~30% of individuals who carry a gene with a disease-causing mutation. Screening families to identify such individuals is important because their risk of an acute attack can be decreased by counseling on avoiding potential precipitants (1, 4).
