Molecular survey of a prevalent mutation, ⁹⁸⁵A-to-G transition, and identification of five infrequent mutations in the Medium-Chain Acyl-CoA Dehydrogenase (MCAD) gene in 55 patients with MCAD deficiency

Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is an inborn error of fatty-acid oxidation that is characterized by fasting intolerance and recurrent episodes of hypoglycemic coma which can be fatal. Its incidence is one of the highest among genetic metabolic disorders. Using a modified PCR and NcoI digestion method, we have surveyed 46 additional, unrelated MCAD-deficient patients for a prevalent mutation, an ⁹⁸⁵A-to-G transition (⁹⁸⁵A→G), that we previously identified in nine MCAD-deficient patients. Among the total of 55 studied, 44 were homozygous and 10 were heterozygous for the ⁹⁸⁵G allele, whereas one did not carry this mutant allele, indicating that the prevalence of the ⁹⁸⁵G allele is 89.1%. Furthermore, we identified five other types of mutation: one each in three of the compound heterozygotes and two in the single non-⁹⁸⁵G patient. An RFLP study of 12 ⁹⁸⁵G-homozygotes showed that all 24 alleles fell into a single haplotype. A questionnaire regarding the ethnic and national origin of their patients was sent to all referring investigators. All 41 patients for whom this information was provided were Caucasians. Of 29 patients whose country of origin was specified, 19 and five were from the British Isles and Germany, respectively. These data suggest that ⁹⁸⁵A→G may have occurred in a single person in an ancient Germanic tribe.