Mild variant of maple syrup urine disease.

The case of a three-year-old boy with mental retardation, moderate muscular hypotony and speech delay is presented. The mild form of maple syrup urine disease was suspected at the first blood screening test by means of ion-exchange thin-layer chromatography. The diagnosis was confirmed by quantitative serum amino acid analysis and protein loading. On a low protein (2 g/kg body weight) diet completed with leucine-isoleucine-valine free formula prompt and lasting normalization of the serum amino acid level ensued with steady improvement of the clinical and neurological status.