Human facial dysostoses.

The human facial dysostoses can be subdivided into mandibulofacial dysostoses (MFDs) and acrofacial dysostoses (AFDs). The craniofacial phenotypes of the two groups of patients are similar. Both types are thought to be related to abnormal migration of neural crest cells to the pharyngeal arches and the face. The craniofacial anomalies shared by the two groups consist of downslanting palpebral fissures, coloboma of the lower eyelid, from which the eyelashes medial to the defect may be absent, hypoplasia of the zygomatic complex, micrognathia, and microtia, which is often associated with hearing loss. These facial deformities are associated with limb anomalies in the AFDs. All MFDs present with the typical craniofacial phenotype, but some have additional features that help to distinguish them clinically: intellectual disability, microcephaly, chest deformity, ptosis, cleft lip/palate, macroblepharon, or blepharophimosis. The limb anomalies in the AFDs can be classified into pre-axial, post-axial, and others not fitting into the first two AFD types. Of the pre-axial types, Nager syndrome and of the post-axial types, Miller syndrome are the best-known disorders of their AFD subgroups. Several other AFDs with unknown molecular genetic bases, including lethal ones, have been described. This article reviews the MFDs and AFDs published to date.