3-Hydroxy-3-methylglutaryl-coenzyme A lyase deficiency: initial presentation in a young adult.

3-Hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) lyase deficiency is a rare inborn error affecting leucine catabolism and ketogenesis, usually presenting in the neonatal period. Late forms of the disease have been detected in infancy and childhood, but not in adults. We report a case of HMG-CoA lyase deficiency with initial presentation in a 29-year-old adult with no prior history of the disease, which to our knowledge is the first case described with presentation at this age.