Apert syndrome (acrocephalosyndactyly type I) is a congenital multisystem disorder defined by multisuture craniosynostosis, midface retrusion, and symmetrical complex bony syndactyly of the hands and feet. Craniosynostosis is a near-universal finding, most commonly involving the coronal sutures, with frequent sagittal and lambdoid involvement; progressive synostosis of additional sutures may develop postnatally. The hand always shows fusion of the middle three digits, with frequent involvement of the thumb and fifth finger; digits 2-4 typically share a single fingernail (synonychia). Syndactyly of the feet involves the lateral three digits, digits 2-5, or all digits. Additional features include cleft palate, dental crowding, conductive and sensorineural hearing loss, ocular findings (proptosis, hypertelorism, strabismus), upper-airway compromise, raised intracranial pressure, hydrocephalus and cervical-spine fusions (commonly C5-C6). Less commonly, congenital heart defects, genitourinary anomalies and acneiform skin involvement may occur. Neurodevelopmental outcomes range from normal intellect to mild intellectual disability, with moderate-to-severe impairment reported in a subset. Inter-individual variability in severity is substantial.
