FECH and erythropoietic protoporphyria: Similarly, in erythropoietic protoporphyria, an autosomal dominant condition caused by mutations in the ferrochelatase (FECH) gene, the penetrance of the pathogenic FECH allele is influenced by the level of expression of the wild-type FECH allele (Gouya et al. 1999; 2002; Di Pierro et al. 2007).