OBJECTIVE: To investigate executive function and adaptive behavior in 
individuals with Muenke syndrome using validated instruments with a normative 
population and unaffected siblings as controls.
STUDY DESIGN: Participants in this cross-sectional study included individuals 
with Muenke syndrome (P250R mutation in FGFR3) and their mutation-negative 
siblings. Participants completed validated assessments of executive functioning 
(Behavior Rating Inventory of Executive Function [BRIEF]) and adaptive behavior 
skills (Adaptive Behavior Assessment System, Second Edition [ABAS-II]).
RESULTS: Forty-four with a positive FGFR3 mutation, median age 9 years, range 7 
months to 52 years were enrolled. In addition, 10 unaffected siblings served as 
controls (5 males, 5 females; median age, 13 years; range, 3-18 years). For the 
General Executive Composite scale of the BRIEF, 32.1% of the cohort had scores 
greater than +1.5 SD, signifying potential clinical significance. For the 
General Adaptive Composite of the ABAS-II, 28.2% of affected individuals scored 
in the 3rd-8th percentile of the normative population, and 56.4% were below the 
average category (<25th percentile). Multiple regression analysis did not 
identify craniosynostosis as a predictor of BRIEF (P = .70) or ABAS-II scores (P 
= .70). In the sibling pair analysis, affected siblings performed significantly 
poorer on the BRIEF General Executive Composite and the ABAS-II General Adaptive 
Composite.
CONCLUSION: Individuals with Muenke syndrome are at an increased risk for 
developing adaptive and executive function behavioral changes compared with a 
normative population and unaffected siblings.