GLOBAL INTELLECTUAL DEFICITS IN CYSTINOSIS

Fourteen families of children with infantile nephropathic cystinosis w ere evaluated using the Stanford-Binet Intelligence Scale, Fourth Edit ion [Thorndike et al., 1986: Stanford-Binet Intelligence Scale, Fourth Ed.]. The IQs of 15 children with cystinosis, their 23 sibs and 24 pa rents were compared in order to evaluate a potential effect of cystino sis on intelligence. Children with cystinosis had a significantly lowe r mean IQ than their sibs and their parents (P = .001). Thus, even tho ugh the mean IQ of the children with cystinosis (94.4 +/- 10) was with in the average range, there is evidence that these children have a mil d global intellectual deficit relative to their expected IQ based upon the IQs of other relatives. In addition, to a subset of the subjects we administered a measure of scholastic ability, the Wide Range Achiev ement Test-Revised [Jastak and Wilkinson, 1984: The Wide Range Achieve ment Test-Revised], which consists of spelling, reading, and arithmeti c subtests. The 11 cystinosis subjects scored significantly lower (P = .01) than their 16 sibs and their 14 parents in the area of spelling, whereas they did not significantly differ in their performance in the areas of reading and arithmetic.