Intellectual and school performances in early-treated classical PKU patients. The French collaborative study.

Abstract

We did not observe any loss of mean IQ scores measured at 11 when PKU diet was stopped as early as 5 years of age compared to 8 years. Nevertheless, 44% of these children presented learning disabilities and repeated one or more school years. These difficulties appear before or at early elementary school level and are independent of the age of diet discontinuation between 5 and 8 years. They seem to be related to perceptual motor dysfunction, suggesting the possibility of a specific deficit that could seriously interfere with academic progress but which is not accompanied by obvious impairment of overall intellectual functioning [1, 4–7, 9]. Among the children who repeated at least 1 year, there was a much higher percentage of pupils who repeated 2 or more school years than in the scholar national average population. The most important factor related to these difficulties seems to be the parents' socioeconomic status, which is also correlated with the children's IQ scores. This influence is not due to the quality of the diet, which is roughly similar for all the patients whatever their school performance. PKU seems to amplify learning difficulties already present in unaffected siblings. Whether the difficulties would be avoided by continuing the diet throughout elementary school remains undemonstrated.