The social behavioral phenotype of Kabuki syndrome.

OBJECTIVE: This study describes the social-communication and behavioral profile associated with Kabuki syndrome (KS), including exploratory comparisons between individuals with a pathogenic variant in KMT2D (KS1) versus KDM6A (KS2). METHOD: Thirty-five caregivers of children/adults with KS (25F, Mage = 13.45, SD = 7.60) completed the Social Responsiveness Scale 2nd Edition (SRS-2), Colorado Learning Difficulties Questionnaire, and/or Strengths and Difficulties Questionnaire. Descriptive analyses and non-parametric tests were conducted to examine behavioral trends in the entire cohort and to explore differences in social behaviors and autism characteristics between those with KS1 versus KS2. RESULTS: About a third of the sample have a prior diagnosis of autism spectrum disorder, with rates more elevated in KS2 versus KS1 (67% vs. 23%). In the full cohort, 72% fell in borderline/clinical ranges for Peer Problems, while only 3% yielded atypical scores for Prosocial Behaviors. Those with KS1 were rated to show most challenges in restricted/repetitive behaviors (RRBs), which fell in the moderately severe range, compared to other social domains (social communication, social awareness, social motivation). In contrast, social motivation was the sole area rated within normal limits. CONCLUSION: Those with KS2 showed greater difficulties across all social behavior/cognitive domains than KS1 counterparts, albeit both presented with similar severity in RRB and prosocial behaviors. Prominent features of the KS social behavioral phenotype include pronounced difficulties with inflexible behaviors and restricted interests juxtaposed with strong prosocial tendencies. KS2 may confer increased risk for autism-related characteristics, underscoring the need for more systematic investigations.