C syndrome

C syndrome, also known as Opitz trigonocephaly syndrome or trigonocephaly C syndrome (Orphanet code 1308), is an extremely rare multiple congenital anomaly syndrome first described by John Opitz in 1969. The hallmark feature is trigonocephaly, a distinctive triangular shape of the forehead caused by premature fusion (craniosynostosis) of the metopic suture. The condition affects multiple body systems including the craniofacial skeleton, central nervous system, limbs, heart, kidneys, and genitalia. Key clinical features include trigonocephaly, a broad nasal bridge, upslanted palpebral fissures, epicanthal folds, short nose, micrognathia (small jaw), low-set ears, redundant skin folds, and a short neck. Limb anomalies such as polydactyly (extra digits), syndactyly (fused digits), and joint contractures are frequently observed. Congenital heart defects, renal anomalies, and genital abnormalities (particularly cryptorchidism and hypospadias in males) are also commonly reported. Intellectual disability of variable severity is a consistent feature. Some affected individuals may also have visceral anomalies including intestinal malrotation. The genetic basis of C syndrome has been debated. Some cases have been linked to mutations in the CD96 gene (also known as TACTILE) on chromosome 3q13.13, which encodes a cell surface receptor involved in cell adhesion, though genetic heterogeneity is suspected. The prognosis varies considerably; some patients have a severe presentation with early lethality, while others survive into childhood or beyond. Treatment is symptomatic and supportive, and may include surgical correction of craniosynostosis, repair of congenital heart defects, and developmental support services. A multidisciplinary approach involving craniofacial surgery, cardiology, nephrology, and developmental pediatrics is typically required.

Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.

Common questions about C syndrome