Apert Syndrome is a rare but extremely severe acrosyndactlyly that affects cranial structures as well as fingers and toes during embryonic and fetal development. Mutations in the fibroblast growth factor receptor-2 (FGFR2) results in constant active signaling, which in turn, prohibits the normal interdigit differentiation process. This mutation is found in chromosome 10b. The defect is inherited in autosomal fashion and the phenotype shows all digits joined together. Despite the current understanding of the underlying genetic abnormalities, the clinical appearance of these children is usually sporadic.
Incidence and Associated Conditions
- CA Birth Defects Monitoring Program reported incidence of 1 in 81,000 out of ~2.5M live births; Craniofacial Center at the North Texas Hospital for Children reported an incidence of 1 in 65,000 live births
- Associated with Crouzon syndrome, Pfeiffer syndrome, Saethre-Chotzen syndrome, Mandibular prognathism
Associated Findings
- Craniofacial: hyperacrobrachycephaly, craniofacial asymmetry, steep wide forehead, flat occiput, downslanting palpebral fissures, divergent upgaze, esotropic downgaze, depression of nasal bridge, ocular hypertelorism and proptosis, short and wide nose with bulbous tip and reduced anterior facial height
- Oral: cleft palate, bifid uvula, impacted teeth, delayed or ectopic eruption, supernumerary teeth, thick gingiva, anterior and posterior open bite and cross bite
- Skeletal: syndactyly of hands and feet, decreased glenohumeral mobility, radiohumeral synostosis, pectus excavatum, flattening of the chest wall, asymmetric chest wall, spina bifida, hemivertebrae, spinal fusions, scoliosis, lordosis, wide interpubic distance, genua valga and osseous ankylosis at the knees
- Cutaneous: hyperhidrosis, oily skin, resistant acne, interrupted eyebrows, excessive forehead wrinkling, lateral plantar hyperkeratosis, skin dimpling over joints and oculocutaneous hypopigmentation
- Neurological: megalencephaly, ventriculomegaly, corpus callosum anomalies, hippocampal hypoplasia or dysplasia, septum pellucidum hypoplasia or dysplasia, cerebral cortex dysplasia and anomalies of gyral patterning
Classification
- Type I: "spade" hand; most common and least severe; thumb shows radial deviation and clinodactyly but is separated from the first finger; three middle fingers have normal length and are fused together; simple syndactyly in fourth web space
- Type II: "spoon" or "mitten" hand; thumb is fused to first finger by simple complete or incomplete syndactyly; digits are fused at the distal interphalangeal joints, so a concave palm is formed
- Type III: "hoof" or "rosebud" hand; most uncommon but most severe deformity; solid osseous or cartilaginous fusion of all digits; thumb is turned inward
