Intellectual performance of children with maple syrup urine disease.

The intellectual performance of 22 children aged 3-16 years with maple syrup urine disease (MSUD) was assessed and compared to a group of early treated phenylketonuria (PKU) children and normal subjects matched by age, sex, nationality, and socio-economic status. All subjects were tested by one examiner only using the age related versions of the non-verbal Snijders-Oomen intelligence test. The mean IQ (+/- SD) score was 74 +/- 14 (range 50-103) in patients with MSUD, 101 +/- 12 (range 87-125) in early treated PKU patients, and 107 +/- 9 (range 90-122) in normal subjects. Intercorrelations indicated that length of time after birth that plasma leucine concentration remained > 1 mmol/l and quality of long-term metabolic control have important influences on IQ.