Saethre-Chotzen syndrome

Saethre-Chotzen syndrome (SCS), also known as acrocephalosyndactyly type 3 (ACS III) and Chotzen syndrome, is a very rare autosomal dominant congenital disorder characterized by acrocephalosyndactyly, craniosynostosis (premature closure of one or more of the sutures between the bones of the skull). It is caused by mutations in the TWIST transcription factor (TWIST) gene.

Characteristics
Classic features include:
 * 1) synostosis of the coronal sutures of the skull resulting in characteristic faces including ptosis, facial asymmetry and small ears
 * 2) syndactyly of the fingers, particularly of the second and third digits
 * 3) Intelligence is usually normal. Some affected individuals may have mild to moderate mental retardation.

Cause and genetics
SCS is caused by a mutation in the TWIST gene, located on human chromosome 7p21. Autosomal dominant inheritance indicates that the defective gene responsible for a disorder is located on an autosome (chromosome 7 is an autosome), and only one copy of the gene is sufficient to cause the disorder, when inherited from a parent who has the disorder.

Epidemiology
The incidence of this rare syndrome is estimated at between 1 in 25,000–50,000 live births.