Genetic Subtypes of Apert Syndrome Are Associated With Differences in Airway Morphology and Early Upper Airway Obstruction.

BACKGROUND: Apert syndrome is predominantly caused by 2 paternally inherited gain-of-function mutations in the FGFR2 gene, Pro253Arg, and Ser252Trp. Studies comparing phenotypic features between these 2 mutations have established differences in syndactyly severity and incidence of cleft palate. Obstructive sleep apnea can be debilitating in a subset of patients with Apert syndrome, yet is not well understood. This study aims to determine whether FGFR2 mutations impart differential effects on airway physiology and morphology.

METHODS: Patients with Apert syndrome and confirmatory molecular testing were reviewed for polysomnography, nasal endoscopy, microlaryngoscopy and bronchoscopy, and computed tomography imaging. Obstructive apnea-hypopnea index and oxygen saturation nadir, nasal airway volumes, choanal cross-sectional area, and midfacial cephalometric dimensions were compared across mutation types.

RESULTS: Twenty-four patients (13 Ser252Trp, 11 Pro253Arg) were included. Severe obstructive sleep apnea (obstructive apnea-hypopnea index>10) occurred in 8 (62%) patients with Ser252Trp mutations compared with 1 (9%) patient with Pro253Arg mutations (P=0.009). Computed tomography imaging at 1 year of age demonstrated that nasopharyngeal airway volumes were 5302±1076 mm3 in the Ser252Trp group and 6832±1414 mm3 in the Pro253Arg group (P=0.041). Maxillary length (anterior nasal spine-posterior nasal spine, P=0.026) and basion-anterior nasal spine (P=0.007) were shorter in patients with Ser252Trp mutations.

CONCLUSIONS: The findings suggest that the Ser252Trp mutation in Apert syndrome is associated with higher severity obstructive sleep apnea and decreased nasopharyngeal airway volume. Heightened clinical awareness of these associations may inform treatment planning and family counseling.