Identification of a novel compound heterozygous genotype of hereditary methemoglobinemia type I

Objective To identify the mutation in NADH-cytochrome b5 reductase (b5R) gene in a patient with hereditary methemoglobinemia type I.Methods The cDNA of b5R gene coding sequence from the patient was analyzed by directly sequencing the RT-PCR product and the result was further confirmed by restriction endonuclease digestion of the genomic DNA fragments from the patient, his parents and a normal control.Results A CTC →CCC mutation was found in one b5R allele of the patient,at codon 72 in exon 3,causing the replacement of Leu by Pro.In another b5R allele of the patient,at codon 203 (TGC→TAC) in exon 7,leading to the substitution of Tyr for Cys.Conclusion A novel genotype,L72P/C203Y,was determined in a Chinese patient with hereditary methemoglobinemia type I.