Fibroblast growth factor receptor 2: A mutation (change) in the fibroblast growth factor receptor 2 (FGFR2) gene on chromosome 10 causes the best-known type of acrocephalosyndactyly, namely Apert syndrome which is characterized by abnormalities of the skull and face and the hands and feet. There is premature closure of some of the sutures of the skull (craniosynostosis) resulting in an abnormally shaped head (which is unusually tall but short from front-to-back) and an abnormally shaped face with shallow eye sockets and underdevelopment of the midface. There is fusion of fingers and toes (syndactyly) and broad ends of the thumbs and big toes. Surgery is often useful with the skull, face, hands and feet. Different mutations in FGFR2 are responsible for two other genetic diseases, namely, Pfeiffer syndrome (another type of acrocephalosyndactyly) and Crouzon syndrome (purely a craniofacial disorder with no hand or foot problems). All are inherited as dominant traits.