From Cognitive Processing to Daily Functioning: Language, Visuomotor Integration, and Adaptive Behavior in Children With Coffin-Siris Syndrome

Studying Mendelian neurodevelopmental disorders (NDDs) from a bottom-up perspective, in which neurocognitive functioning is conceptualized as a mediator between genotype and behavioral phenotype, may facilitate early identification of syndrome-specific vulnerabilities. This study characterizes the neurocognitive phenotype and adaptive functioning of children with Coffin-Siris syndrome (CSS), a rare Mendelian NDD with unknown effects on brain development. Thirty-five children with CSS (Mage = 9.74 years, SD = 4.22) underwent performance-based assessment of global cognition, receptive and expressive language, and visuomotor integration. Parents completed standardized questionnaires assessing adaptive functioning. The predictive value of age and cognitive performance for adaptive outcomes was explored. Children with CSS showed marked developmental delays across global cognition and domain-specific skills. Receptive language emerged as a relative strength, whereas expressive language and visuomotor integration were prominent vulnerabilities. Adaptive functioning was broadly impaired, particularly in communication, self-regulation, being part of the community, and daily functioning. Older children showed larger divergence from age-expected norms, consistent with a growing-into-deficit pattern. Receptive language, expressive language, and visuomotor integration each uniquely contributed to adaptive behavior, independent of global cognitive level. These findings underscore the importance of individualized neurocognitive assessment to guide targeted interventions improving daily functioning in children with CSS.