FECH and autosomal erythropoietic protoporphyria: EPP can be caused by three different genetic aberrations (Lecha et al., 2009): (1) an activating mutation in ALAS2; (2) compound heterozygous or homozygous FECH mutations resulting in a recessive form; and (3) the combination of a strongly hypomorphic or null mutation of one FECH allele in trans to a C-polymorphism (instead of T) at position −48 with respect to the 3′ splice site of exon 4 (c.315-48C).