Craniosynostosis: Premature fusion of the cranial sutures (the fibrous joints between the bones of the skull) in an infant, preventing normal growth of the baby's head. Craniosynostosis involving some but not all of the sutures causes an abnormally shaped skull. Premature closure of all of the sutures results in microcephaly (an abnormally small head) which arrests the normal growth and development of the baby's brain and may result in developmental delay and mental retardation. Early detection of the condition is therefore of great importance. Treatment is surgery designed to keep the sutures open.
Craniosynostosis can occur as an isolated abnormality or as part of a syndrome. A number of craniosynostosis syndromes are now known to be due to mutations in the FGFR genes (FGFR = fibroblast growth factor receptor). The FGFR-related craniosynostosis syndromes include established entities (the Apert, Crouzon, and Pfeiffer syndromes) and several newer entities (the Beare-Stevenson, Muenke, and Jackson-Weiss syndromes). All are inherited in an autosomal dominant manner. Affected individuals have a 50% chance of passing the mutant gene to each child. Prenatal testing is available.