In a black female infant presenting in the neonatal period with persistent hypotonia, Roe et al. (1990) found deficiency of 2,4-dienoyl-coenzyme A reductase. Biochemical studies had shown hyperlysinemia, hypocarnitinemia, a normal organic acid profile, and an unusual acylcarnitine ... In a black female infant presenting in the neonatal period with persistent hypotonia, Roe et al. (1990) found deficiency of 2,4-dienoyl-coenzyme A reductase. Biochemical studies had shown hyperlysinemia, hypocarnitinemia, a normal organic acid profile, and an unusual acylcarnitine species in both urine and blood. The latter metabolite was identified by mass spectrometry as 2-trans,4-cis-decadienoylcarnitine, derived from incomplete oxidation of linoleic acid. In spite of dietary therapy, the patient died of respiratory acidosis at 4 months of age. Samples of liver and muscle taken at autopsy showed that the level of 2,4-dienoyl-coenzyme A reductase activity was 40% of the control value in liver and only 17% of that found in normal muscle. Roe et al. (1990) stated that this was the first report of a patient with unsaturated fatty acid oxidation.