is a very rare disorder that is characterized by abnormalities affecting the head and facial (craniofacial) region. Major physical features may include widely spaced eyes (ocular hypertelorism); a flat, broad nose; and a widow's peak hairline. In some cases, the tip of the nose may be missing; in more severe cases, the nose may separate vertically into two parts. In addition, an abnormal skin-covered gap in the front of the head (anterior cranium occultum) may also be present in some cases. Other features may include a cleft lip, other eye abnormalities (coloboma, cataract, microphthalmia), hearing loss, and/or agenesis of the corpus callosum. The majority of affected individuals have normal intelligence. The exact cause of frontonasal dysplasia is not known. Most cases occur randomly, for no apparent reason (sporadically). However, some cases are thought to run in families. Researchers have suggested that this condition is caused by mutations in the ALX3 gene and is inherited in an autosomal recessive fashion. Source: Genetic and Rare Diseases Information Center (GARD), supported by ORDR-NCATS and NHGRI.