Binder phenotype: associated findings and etiologic mechanisms.

Binder phenotype (BP), or maxillonasal dysostosis, consists of 6 characteristics: arhinoid face, abnormal position of nasal bones, intermaxillary hypoplasia/malocclusion, reduced/absent anterior nasal spine, atrophy of nasal mucosa, and absence of frontal sinus. The purposes of this study were (1) to review the characteristic facial findings, other malformations, and diagnoses in 8 patients with BP; (2) to compare these patients to those in the literature; and (3) to discuss developmental mechanisms, including genetic and environmental factors, involved in this facial defect. An initial 24 cases of BP were identified from the Iowa Registry of Congenital & Inherited Disorders during the period of 1998 to 2008. Chromosome analysis performed in all 24 cases revealed the following: trisomy 21, trisomy 18, and mosaic trisomy 18. Of the 24 patients, 8 met the specific diagnostic characteristics of BP. All 8 patients were evaluated in the genetics clinic at University of Iowa Children's Hospital, having diagnoses of vitamin K epoxide reductase deficiency, Xp22.3 deletion with chondrodysplasia punctata, Stickler syndrome, fetal warfarin syndrome, Robinow syndrome, and unknown etiology. This study, unlike those in the literature, ascertained cases through a population-based active surveillance registry and therefore may better represent the incidence of BP (∼1 per 18,000). Most cases were sporadic with a recognizable pattern of malformation, highlighting that chromosomal, genetic, and exogenous factors may cause BP. Of 8 cases remaining after exclusion of chromosome syndromes, 3 cases had in common the involvement of the vitamin K-dependent metabolic pathway, which likely represents a significant pathogenetic mechanism of BP. Clinical characterization of BP, as in these cases, may allow further understanding of other causative developmental mechanisms.