G syndrome is a genetic disorder characterized by the association of distinctive craniofacial anomalies, genito-urineal malformations, and abnormalities of the larynx, pharynx and/ or trachea. Craniofacial anomalies of the G syndrome include widely set eyes (hypertelorism), cleft palate/lip, palpebral fissures, epicanthal folds, posteriorly oriented external ears, and a wide nasal bridge. Genito-urineal malformations in the affected males may include cryptorchidism, bifid scrotum, or hypospadias. Defective swallowing with regurgitation and a horse cry, wheezing and stridorous respiration is consistently present as a result of larynx, pharynx and/or trachea abnormalities. Sometimes, the abnormalities may involve the ventral midline, lungs (hypoplasia), anal opening (imperforate anus), corpus callosum (hypoplasia or agenesis), and heart. Mental retardation can also be one of the clinical features. Ultrasonography is the best recommended prenatal diagnosis method for G syndrome. Multidisciplinary management is required for each patient and alternative feeding methods should be proposed.

It is known that 80% of the X-linked opitz syndrome is caused by mutations in the midline 1 (MID 1) gene. Normally, MID 1 gene encodes the midline 1 protein. Scientists propose that MID1 is a microtubule-associated protein that influences microtubule dynamics in MID1-overexpressing cells. However, the exact pathogenesis of Opitz syndrome remains unknown.