Saethre–Chotzen syndrome with an atypical phenotype: identification of TWIST microdeletion by array CGH.

Saethre–Chotzen syndrome is a very rare autosomal dominant congenital disorder characterized by craniosynostosis and acrocephalosyndactyly. It is caused by a mutation in TWIST1, located on chromosome 7p21. A shortage of functional TWIST1 protein affects the development and maturation of cells in the skull, face, and limbs. The patient described in this report displayed craniofacial features classic for Saethre–Chotzen syndrome, including craniosynostosis, low-set ears, small pinna with prominent crura, a high-arched palate, and a simian crease on the left hand. He did not have the limb anomalies commonly seen in patients with Saethre–Chotzen syndrome, and the results of conventional chromosome analysis were normal. However, results of a microarray-based comparative genomic hybridization (array CGH) study confirmed the karyotype of46,XY.7p21.1p15.3(15,957,375-20,331,837)x1, a region that includes TWIST1. Subsequent fluorescent in situ hybridization analysis confirmed this result. No other chromosome was involved in the rearrangement. This case illustrates the important contribution of array CGH to the identification of TWIST microdeletions, even in a patient not showing the phenotype typical of Saethre–Chotzen syndrome.