The genetic cause of the disease, in the majority of patients, is a partial deficiency in ferrochelatase, the last enzyme in the heme biosynthetic pathway.47 The inheritance of ferrochelatase deficiency EPP is complex and is usually associated with an inheritance of a mutated ferrochelatase (FECH) allele from one parent, and a low-expression allele (IVS-48T/C) from the other.48 Consequently, the residual activity of ferrochelatase is decreased below a critical threshold, leading to an overt disease of EPP. This evidence concerns the gene FECH and autosomal erythropoietic protoporphyria.