CYBRD1 and porphyria cutanea tarda: Additionally, other genes important for iron regulation could be involved, as indagated in a population of 74 PCT South African patients, who underwent sequencing analysis of the promoter region of four genes that are involved in iron metabolism (ceruloplasmin (CP), cytochrome b reductase 1 (CYBRD1), hepcidin antimicrobial peptide (HAMP) and ferroportin or solute carrier family 40 member A1 (SLC40A1)).