The language phenotype of children and adolescents with Noonan syndrome

Abstract

Purpose: This study presents an analysis of language skills in individuals with Noonan syndrome (NS), an autosomal dominant genetic disorder. We investigated whether the language impairments affecting some individuals arise from deficits specifically within the linguistic system or whether they are associated with cognitive, perceptual, and motor factors. Comparisons of language abilities among the different NS genotypes were also conducted.

Method: Sixty-six children and adolescents with NS were evaluated using standardized speech, language, and literacy assessments. Additional cognitive, perceptual, and motor tasks were administered to examine the relation of these factors to language development. Genotype was noted for those who underwent genetic testing.

Results: Language impairments were more frequent in NS than in the general population and were associated with higher risk for reading and spelling difficulties. Language was significantly correlated with nonverbal cognition, hearing ability, articulation, motor dexterity, and phonological memory. Genotype analyses suggest that the higher performance of SOS1-positive than PTPN11-positive individuals on language tasks was largely mediated by differences in cognitive ability.

Conclusions: Our results indicate that variation in language skill in NS is closely related to cognitive, perceptual, and motor factors. It does not appear that specific aspects of language are selectively affected in this syndrome.

Figure 1

Distribution of language scores (core language scores on the Clinical Evaluation of Language Fundamentals—Preschool, Second Edition [CELF–P2] and the Clinical Evaluation of Language Fundamentals, Fourth Edition [CELF–4]) among children and adolescents with Noonan syndrome (n = 66), with a normative population curve displayed.

Figure 2

Correlation between language and nonverbal cognitive ability in individuals with Noonan syndrome. DAS = Differential Ability Scales.

Figure 3

Model depicting the relationship between Noonan syndrome genotype (PTPN11 vs. SOS1 mutation) and language ability, with nonverbal cognitive ability as a mediator. a = effect of genotype on cognitive ability (mediator); b = effect of nonverbal cognitive ability on language ability (outcome variable); c′ = effect of genotype on language ability, controlling for nonverbal cognition. ns = not significant. **p < .01. ***p < .001.