Inherited disorders of mitochondrial fatty acid oxidation: a new responsibility for the neonatologist.

The disorders of mitochondrial fat oxidation present clinically with three major clinical phenotypes: hypoketotic hypoglycemia, cardiomyopathy, and myopathy. Although these features can present together in some of the disorders, one will be the dominant clinical problem. This review will describe these clinical phenotypes while addressing the diagnostic value of various clinical and laboratory studies which are often used for making these diagnoses. With knowledge of the clinical presentation, these diagnoses can often be made very rapidly and at relatively low cost by more specific laboratory tests. The increasing availability of expanded newborn screening by tandem mass spectrometry as well as prenatal diagnosis for these often fatal disorders now provides the opportunity for pre-symptomatic diagnosis. The neonatologist is now in the unique position of identifying these inherited disorders prior to or during severe symptom onset and has the earliest opportunity to provide successful treatment intervention.