Macrostomia: a spectrum of deformity.

BACKGROUND: Macrostomia is a rare facial cleft, with an incompletely described pathogenesis. This series highlights cases of isolated macrostomia presenting with several distinct phenotypes. We examine phenotypic differences in macrostomia patients, to further elucidate the etiopathogenesis. MATERIALS AND METHODS: We performed a retrospective review of macrostomia patients evaluated during a 10-year period. Patient demographics and clinical features are reported. RESULTS: We identified 25 macrostomia patients (13M/12F). Right-sided macrostomia occurred in 15, left-sided macrostomia occurred in 6, and bilateral macrostomia occurred in 4 patients. Of the bilateral cases, 100% existed in isolation of craniofacial microsomia (CFM) or other craniofacial abnormalities. Twelve patients presented with macrostomia in isolation of CFM; in this subgroup, the male-to-female ratio was 1:1. Bilateral macrostomia was present in 33% of patients. Unilateral macrostomia occurred more often on the right (5:2). Phenotypes included simple unilateral or bilateral macrostomia (67%), macrostomia associated with severe diastasis of the cheek musculature (8%), macrostomia associated with lateral facial clefts (17%), and diastasis of cheek musculature without significant macrostomia (8%). CONCLUSIONS: Macrostomia seen in isolation of CFM presents in phenotypically distinct forms. It is unlikely that a single mechanism is responsible for this range of phenotypes. We believe that both intrauterine trauma and failure of fusion of the mandibular and maxillary processes secondary to an aberration in FGF8 function are responsible. Additionally, diastasis of facial musculature may result from delayed fusion and subsequent decreased mesodermal penetration of the mandibular and maxillary processes.