3C syndrome

The 3C syndrome, also known as Ritscher-Schinzel syndrome, is a rare, presumably autosomal recessive syndrome characterized by craniofacial, cerebellar, and cardiac anomalies. Cardiac manifestations include ventricular septal defect, atrial septal defect, tetralogy of Fallot, double outlet right ventricle, hypoplastic left heart, aortic stenosis, pulmonic stenosis, and other valvular anomalies. Central nervous system anomalies include Dandy-Walker malformation, cerebellar vermis hypoplasia, and enlargement of the cisterna magna. Craniofacial abnormalities seen are cleft palate, ocular coloboma, prominent occiput, low-set ears, hypertelorism, down-slanting palpebral fissures, depressed nasal bridge, and micrognathia. The phenotypic manifestations can vary and cardiac and cerebellar manifestations are not always present. A recent study identified homozygous sequence variants affecting the KIAA0196 gene, which encodes the WASH (Wiskott-Aldrich Syndrome Protein and SCAR Homolog) complex protein strumpellin as causal to a form of 3C syndrome. Another study showed that a missense variant in CCDC22 is associated with a form of X-linked intellectual disability with features of 3C syndrome.