Hereditary coproporphyria

Hereditary coproporphyria, abbreviated HCP, is a disorder of heme biosynthesis and is classed as an acute hepatic porphyria. It results from a deficiency of the enzyme coproporphyrinogen oxidase, which is coded by the CPOX gene, and it is inherited in an autosomal dominant fashion, although a few people with two affected copies have been identified. People with HCP can have the acute attacks seen in other acute porphyrias, which involve abdominal pain, vomiting and neurological dysfunction, and unlike acute intermittent porphyria they may also show skin findings resembling porphyria cutanea tarda. Attacks can be triggered by certain drugs, environmental stressors or changes in diet. Biochemical and molecular testing are used to confirm a porphyria and identify the specific genetic defect. Porphyrias are rare overall, with a combined incidence estimated at about one in 20,000, and the exact incidence of HCP is hard to pin down because of its reduced penetrance.