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Greig cephalopolysyndactyly syndrome (GCPS) is a pleiotropic, multiple congenital anomaly syndrome. It is rare, but precise estimates of incidence are difficult to determine, as ascertainment is erratic (estimated range 1-9/1,000,000). The primary findings include hypertelorism, macrocephaly with frontal bossing, and polysyndactyly. The polydactyly is most commonly preaxial in the feet and postaxial in the hands, with variable cutaneous syndactyly, but the limb findings vary significantly. Other low frequency findings include central nervous system (CNS) anomalies, hernias, and cognitive impairment. GCPS is caused by loss of function mutations in the GLI3 transcription factor gene and is inherited in an autosomal dominant manner. The disorder is allelic to Pallister-Hall syndrome and one form of the acrocallosal syndrome. Clinical diagnosis is challenging because the findings of GCPS are relatively non-specific, and no specific and sensitive clinical criteria have been delineated. A presumptive diagnosis of GCPS can be made if the patient has the classic triad of preaxial polydactyly with cutaneous syndactyly of at least one limb, hypertelorism, and macrocephaly. Patients with a phenotype consistent with GCPS (but which may not manifest all three attributes listed above) and a GLI3 mutation may be diagnosed definitively with GCPS. In addition, individuals with a GCPS-consistent phenotype who are related to a definitively diagnosed family member in a pattern consistent with autosomal dominant inheritance may also be diagnosed definitively. Antenatal molecular diagnosis is technically feasible. Differential diagnoses include preaxial polydactyly type 4, the GCPS contiguous gene syndrome, acrocallosal syndrome, Gorlin syndrome, Carpenter syndrome, and Teebi syndrome (see these terms). Treatment of the disorder is symptomatic, with plastic or orthopedic surgery indicated for significant limb malformations. The prognosis for is generally excellent. There may be a slight increase in the incidence of developmental delay or cognitive impairment. Patients with large deletions that include GLI3 may have a poorer prognosis. |