Inborn errors of metabolism diagnosed in sudden death cases by acylcarnitine analysis of postmortem bile

Fatty acid oxidation (FAO) disorders represent a frequently misdiagnosed group of inborn errors of metabolism. Some patients die at the first episode of fasting intolerance and, if appropriate investigations are not undertaken, often meet the criteria of sudden infant death syndrome (SIDS). To expand existing protocols for the postmortem diagnosis of FAO and other metabolic disorders, we tested the hypothesis that analysis for acylcarnitine in bile, a specimen readily available at autopsy, may be utilized for diagnostic purposes. Using electrospray/tandem mass spectrometry, we analyzed for acylcarnitine postmortem bile specimens from two infants with long-chain 3- hydroxyacyl-CoA dehydrogenase deficiency, one infant with glutaryl-CoA dehydrogenase deficiency, and 17 uninformative SIDS cases as controls. The affected cases, and none of the controls, showed marked accumulation of C¹⁰-C¹⁸ acylcarnitines or glutarylcarnitine (acyl/free carnitine ratio: 5.2, 2.7, and 1.9, respectively; controls 0.2 ± 0.1). In one patient, all other diagnostic methods were uninformative, suggesting that bile acylcarnitine profiling could lead to identification of previously overlooked cases.