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Saethre-Chotzen Syndrome (SCS) is an inherited craniosynostotic condition, with both premature fusion of cranial sutures (craniostenosis) and limb abnormalities. The most common clinical features, present in more than a third of patients, consist of coronal synostosis, brachycephaly, low frontal hairline, facial asymmetry, hypertelorism, broad halluces, and clinodactyly. The estimated birth incidence is 1/25,000 to 1/50,000 but because the phenotype can be very mild, the entity is likely to be underdiagnosed. SCS is inherited as an autosomal dominant trait with a high penetrance and variable expression. The syndrome is associated with haploinsufficiency of the TWIST1 gene (located on chromosome 7p21.2) encoding the bHLH transcription factor involved in regulating head mesenchyme cell development during cranial tube formation. Some patients with an overlapping SCS phenotype have mutations in the FGFR3 (fibroblast growth factor receptor 3) gene; especially the Pro250Arg mutation in FGFR3 (Muenke syndrome) can resemble SCS to a great extend. Significant intrafamilial and interfamilial phenotypic variability is present for TWIST mutations. |