• Y Wang, C Huang, Y Wu, F Lan, Y Tang, and Z Zhu.
• Center for Medical Laboratory, Fuzhou General Hospital, Fuzhou 350025, China.
• Chinese Med J Peking. 1999 Nov 1; 112 (11): 103210351032-5.

ObjectiveTo investigate the molecular mechanism of recessive congenital methemoglobinemia (RCM) in Chinese and to establish a gene diagnostic method of polymerase chain reaction-restricted fragment length polymorphism (PCR-RFLP).MethodsTotal RNA was isolated from the peripheral leukocytes of the propositus and b5R cDNA synthesized by reverse transcription-polymerase chain reaction (RT-PCR). The coding region of b5R cDNA was analyzed by sequencing of the RT-PCR products.ResultsBoth propositi A and B were found to be homozygotes for a G to A transition at codon 57 in exon 3, changing a guanine to an adenine. This point mutation was not an artificial occurrence during polymerase chain reaction (PCR), as confirmed by Msp I restriction enzyme analysis of the genomic DNA. Propositus A's mother and propositus B's sister and her nephew were found to be heterozygotes for the mutation.ConclusionA guanine-to-adenine transition at codon 57, replacing arginine with glutamine, was the molecular basis for RCM in two Chinese families.

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