To characterize the mutation in NADH-cytochrome b5 reductase gene in a Chinese hereditary methemoglobinemia patient, and elucidate the molecular basis of the disease.

B5R gene from a propositus was analyzed by sequencing the RT-PCR products as well as cDNA clones; and the results were further confirmed by restriction enzyme analysis of the genomic DNA fragments.

A novel mutation was found at codon 72 of b5R gene from the propositus.

Replacement of Leu with Pro at codon 72 of b5R gene is the molecular basis of the propositus; and the mutant allele located in 5′ part of b5R gene mainly cause hereditary methemoglobinemia type Ⅰ.

Hereditary methemoglobinemia; Cytochrome b5 reductase; Polymerase chain reaction; Gene mutation