Apert syndrome: A malformation syndrome characterized by a high short skull, underdevelopment of the midface, soft tissue and bony ("mitten glove") fusion of fingers and toes, fusion of the neck vertebrae, and varying degrees of developmental delay/mental retardation. The frequency of the syndrome rises with the age of the father reflecting the fact that the mutation rate among males rises with their age. Moreover, the mutation that causes Apert syndrome affords the sperm a selective advantage. The mutation is in the gene for fibroblast growth factor receptor 2 (FGFR2) on chromosome 10. Different mutations in FGFR2 are also responsible for two other similar genetic diseases, namely, Pfeiffer syndrome and Crouzon syndrome. See also: Acrocephalosyndactyly.