What is the most characteristic feature of Crouzon syndrome?

Crouzon syndrome (craniofacial dysostosis) is an autosomal dominant condition caused by mutations in the FGFR2 gene. Its defining feature is craniosynostosis — the premature fusion of multiple cranial sutures — which prevents normal skull growth and results in abnormal head shape, midface hypoplasia, exophthalmos (protruding eyes), hypertelorism, and a class III malocclusion due to maxillary underdevelopment. Dental manifestations include an anterior open bite, crossbite, and crowding. Unlike other craniofacial syndromes (e.g., CHARGE syndrome), coloboma and ear malformations are not characteristic of Crouzon syndrome. Intelligence is typically normal.