Juvenile multiple sclerosislike episodes associated with a defect of mitochondrial beta oxidation

We describe a young girl who presented with recurrent episodes of central nervous system (CNS) demyelination mimicking multiple sclerosis. Metabolic evaluations and decreased oxidation of [9,10(n)−3H] palmitate demonstrated defective mitochondrial beta oxidation, but complementation studies of the patient's cells, fused with cell lines with known defects of beta oxidation, failed to identify a known disorder. While progressive CNS demyelination has occurred in patients with defective peroxisomal very long-chain fatty acid oxidation, this is the 1st time it has occurred with defective mitochondrial beta oxidation. This patient appears to represent a novel disorder of beta oxidation producing intermittent demyelination with profound CNS symptoms. Recognition of the defect led to appropriate therapy, which caused marked clinical improvement.