[Acyl coenzyme A dehydrogenase deficiency of medium-chain fatty acids in a 9-year-old boy with adymia. A rare mitochondrial cytopathy which may be more common than previously assumed].

The medium-chain acyl-CoA dehydrogenase (MCAD) deficiency of mitochondrial beta oxidation has been identified in a nine-year old boy with a very bland course and easy fatigue as the main symptom. Repeated low frequency stimulation test and EMG for excluding a myasthenia gravis, and screening for urinary organic acid excretion were helpful for the diagnosis. The EMG test at the m. trapezius by stimulation of the n. accessorius showed an extreme decrease of muscle power down to 49%. After i.v. injection of Edrophonium the loss of power of 20% was still significant, so that we could exclude a myasthenia gravis, but we had found signs of a generalised defect in cell chemistry. The diagnosis could be confirmed by a positive 3-phenylpropionic acid-test and moleculargenetic proof of the Adenine to Guanine mutation at position 985 in the MCAD cDNA (G985) with the polymerase chain reaction. The incidence of this organic aciduria is probably 1:60,000 in Germany, but with more attention to this disease and diagnosis of cases with bland courses the incidence will be higher. The MCAD-defect should be considered in the differential diagnosis of patients with Reye syndrome-like encephalopathies, non-ketotic hypoglycaemia or sudden unexpected deaths in infancy.