Erythropoietic protoporphyria is caused by inherited deficiency of the haem synthetic enzyme ferrochelatase, and is characterized by lifelong photosensitivity. About 5% of patients also develop rapidly progressive liver failure. Inheritance is considered to be autosomal dominant, with transmission of a single ferrochelatase defect from one parent. We describe a family in which two siblings with protoporphyria suffered from severe photosensitivity and developedhepatic failure requiring liver transplantation. Their asymptomatic parents were heterozygousfor distinct ferrochelatase gene mutations (exon 10 donor site a(+3)→g and 1088T→G). Both mutations disrupt splicing of the transcript and causepartial deficiency of ferrochelatase. The affected offspring were compound heterozygotes for these mutations. These patientssuffered from an autosomal recessive form of protoporphyria characterized by severe photosensitivity and cholestatic liver disease in adolescence. We postulate that hepatic failure in erythropoietic protoporphyria may in some cases represent an autosomal recessive type of ferrochelatase deficiency distinct from the purely dermatological disorder. Studies of disease inheritancein families affected by protoporphyria may help identify those predisposed to develop severe liver complications, a distinction not currently possible.