The ATRX gene (also known as XNP and XH2), located at Xq21.1, contains 35 exons and encodes the ATRX protein. In vitro studies suggest the ATRX protein is involved in chromatin remodeling and regulation of gene expression. Mutations of various types in ATRX have been shown to be associated with alpha-thalassemia X-linked mental retardation (ATRX) syndrome, which is generally characterized by severe to profound mental retardation, distinctive craniofacial features, genital anomalies, and alpha-thalassemia (Gibbons R. Orphanet J Rare Dis. 2006;1:15).