Abstract
A 6-day-old baby with a confirmed diagnosis of maple syrup urine disease has been treated with a diet containing the minimum amounts of leucine, isoleucine and valine required for maintenance of normal or only slightly raised plasma levels. At 1 year of age the mental and neurological status of the child is normal, and it is believed that the controlled diet has prevented the onset of the serious cerebro-degenerative changes that occur with the disease when left untreated. The rapid accumulation in the first few days of the branched-chain amino acids and of their keto acid analogues in the tissue fluids, when the baby was fed on a milk diet, makes it imperative to diagnose the disease as soon as possible and to institute the special diet as rapidly as possible.