New mutation identified in two sisters with adult-onset erythropoietic protoporphyria.

BACKGROUND: Erythropoietic protoporphyria (EPP; OMIM #177000) is a rare disease that usually presents in infancy or early childhood. The uncommon adult-onset EPP is often associated with acquired somatic mutations of the FECH gene, secondary to blood dyscracias. METHODS: We investigated two sisters with adult-onset EPP. RESULTS: We found a novel germline mutation in the FECH gene, in trans with the common hypomorphic IVS3-48C allele. CONCLUSIONS: The adult presentation and identical genotypes of the two sisters suggests that the late development of the condition is to an extent a function of the mutation. The exact mechanism for this delayed penetrance is not clear, although these atypical cases raise the possibility of other genetic or nongenetic disease-modifying factors.