Homozygous variegate porphyria (Q96984)

This disease, a very rare variant of variegate porphyria, is a severe skin and neurologic disease manifesting in early infancy, and characterised by markedly reduced levels of the penultimate enzyme in the heme biosynthetic pathway, protoporphyrinogen oxidase. Variegate porphyria is usually inherited as an autosomal dominant trait, displaying incomplete penetrance, as not all persons carrying a mutation in protoporphyrinogen oxidase gene develop the clinical phenotype. Some of the cases of "homozygous" variegate porphyria would be compound heterozygotes for different missense mutations rather than true homozygotes.