Patterns of cognitive functioning in school-aged children with Noonan syndrome associated with variability in phenotypic expression.

OBJECTIVE: To evaluate the cognitive profiles of children with Noonan syndrome (NS) and to relate these profiles to measures of overall clinical severity.

STUDY DESIGN: Thirty-five children with NS between the ages of 7 and 18 years were tested on their intellectual, psychosocial, and academic functioning. The diagnosis of NS was established on the presence of a typical face, the characteristic heart defect, thorax deformity, short stature, affected first-degree relative(s), and cryptorchidism in male subjects.

RESULTS: The total group of children with NS (n = 35) achieved significantly lower mean full-scale IQ, verbal IQ (VIQ), and performance IQ (PIQ) scores (between 85.9 and 89.3) than expected based on normative data. The individual full-scale IQ scores varied between 48 and 130. Because of this wide range of individual scores, the mean group values are not extremely informative. The mean full-scale IQ for the group with moderate NS (n = 19) is 90.8; for the children with severe NS (n = 16) the mean full-scale IQ is 80.6. The patterns of discrepancies between VIQ and PIQ are: (1) an extreme discrepancy between VIQ and PIQ is most likely to emerge in children with severe NS with (low) average intellectual abilities; (2) children with moderate NS are more likely to attain similarities in VIQ and PIQ scores; and (3) children with moderate NS demonstrate a particular pattern of discrepancy between VIQ and PIQ (ie, VIQ > PIQ).

CONCLUSION: For children with NS, the findings on physical examination are indicative of the pattern of cognitive abilities. NS is not associated with substantial deficits in the level of intellectual functioning or with a single/unitary cognitive pattern. Severe NS expression, however, predicts in part a specific pattern of deficits and capacities in cognitive functioning.