This disorder results from a deficiency of NADH-cytochrome b5 reductase). The disorder demonstrates very well that the clinical disorders resulting from enzyme deficiencies, i.e., inborn errors of metabolism, are inherited as recessives, whereas structural defects, such as brachydactyly and structural anomalies of nonenzymatic proteins, are usually inherited as dominants. The form of methemoglobin with electrophoretically atypical hemoglobin (of which there are several types) is dominant.  Mental deficiency occurs only with the enzyme-deficient recessive form of the disorderMuller et al. (1963) described 3 sibs with methemoglobinemia. They showed deficient ability of erythrocytes to utilize glucose for methemoglobin reduction, but normal reduction of lactate.