A case of methemoglobinemia type II due to NADH-cytochrome b5 reductase deficiency: Determination of the molecular basis

Clinical, biochemical and molecular findings in a patient with methemoglobi nemia type II are described. Furthermore, a comparison between methemoglobi nemia type I and type II, both caused by a deficiency of NADH-cytochrome b5 reductase (b5R), is made. Although the clinical pictures of type I and II are strikingly different, mutations in the diaphorase (DIA1) gene located o n chromosome 22 have been described in both types. In the present patient, two newly identified mutations, both leading to a stop codon in exon 4 (Gln 77Ter) and in exon 6 (Arg160Ter), were found. Identification of different m utations at different positions in the DIA1 gene might shed light on the cl inical and biochemical differences between methemoglobinemia type I and typ e II. Hum Mutat 16:18-22, 2000. (C) 2000 Wiley-Liss, Inc.