Laboratory diagnosis of medium-chain acyl-coenzyme A dehydrogenase deficiency by the amplification refractory mutation system.

We used the amplification refractory mutation system (ARMS)--a polymerase-chain-reaction-based method--to detect the 985 A-to-G mutation of the gene coding for the enzyme medium-chain acyl-CoA dehydrogenase (MCAD). The 985 A-to-G allele is thought to account for approximately 89% of the mutant alleles in this disorder and at least one copy was reported to be present in 98% of affected individuals. ARMS provided a simple and robust method that reliably identified the 985 A-to-G mutant allele in patients either homozygous or heterozygous for this allele. Combined with organic acid analysis, ARMS can provide definitive diagnosis for the great majority of the patients with MCAD deficiency. The method, therefore, should be useful in clinical laboratories involved with the diagnosis of inborn errors of metabolism.