Diagnosis of mitochondrial fatty acid oxidation defects.

Inherited defects of mitochondrial beta-oxidation of fatty acids lead to hypoketotic hypoglycemia during prolonged fasting. Affected patients may present with episodes of a Reye-like illness or even sudden child death. The number of currently detected patients with medium-chain acyl-CoA dehydrogenase deficiency--the most common disease in this area--is indicative of a high frequency, possibly comparable to that of phenylketonuria. A comprehensive system of biochemical analyses is described, which enables the differential diagnosis of the various defects. An indispensable part of the diagnostic system is the gas chromatographic/mass spectrometric analysis of plasma and urinary organic acids. A correct diagnosis is a prerequisite for the installment of specific treatment.