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BACKGROUND: Max Muenke included midface hypoplasia as part of the clinical syndrome caused by the Pro250Arg FGFR3 mutation that now bears his name. Our knockout mouse model of Muenke syndrome demonstrates midface hypoplasia in homozygous recessive mice only, with heterozygotes having normal or mildly deficient midfaces; as the majority of humans with the syndrome are heterozygotes, we set about to investigate the incidence of midface hypoplasia in our institution's clinical cohort.
METHODS: We retrospectively reviewed all patients with a genetic and clinical diagnosis of Muenke syndrome from 1990 to 2014. Review of clinical records and photographs included skeletal Angle Class, dental occlusion, and incidence of orthognathic intervention. Cephalometric
evaluation of our patients was compared to the Eastman Standard Values with the appropriate statistical tests.
RESULTS: 23 patients with Muenke syndrome presented for evaluation and 18 met inclusion criteria with complete data - 7 females and 11 males. Average age of presentation was 0.8 years (0.0-9.4), and patients were followed to an average age of 11.2 years (1.0 - 23.1). Average age at the time of imaging was 9.5 years (0.5 - 22.0). Cephalometric analysis revealed an average SNA of 82.5 (67.8-88.8) and an average SNB of 77.9 (59.6-84.1), and there were each equivalent to controls (p<0.05). 12 patients were noted to be in Class I occlusion, 4 in Class II malocclusion, and 2 in Class III malocclusion. Only one patient (6%) underwent orthognathic surgery for Class III malocclusion. Subgroup analysis by dentition - primary, mixed, permanent - revealed consistency of the maxillomandibular relationships.
CONCLUSIONS: While a part of the original description of Muenke syndrome, clinically significant midface hypoplasia is not a common feature. This data is important, as it allows more accurate counseling of patients and families.