FECH and autosomal erythropoietic protoporphyria: The AF of the FECH low-expression SNP locus c.315-48T>C in the Chinese population was 0.317907, and the predicted prevalence of EPP was 7.51 × 10−5 (7.51 × 10−5, 1.902 × 10−6–4.184 × 10−4).