X-linked alpha-thalassemia/mental retardation syndrome (ATR-X syndrome) is a rare syndromic form of X-linked mental retardation. It is characterized by severe mental retardation in males, characteristic facial appearance, alpha thalassaemia, genital anomalies, skeletal abnormalities, and characteristic posture and/or behavior. ATR-X syndrome is caused by a mutation in the ATRX gene, a critical factor involved in heterochromatin formation at mammalian centromeres and telomeres.
The X-linked mental retardation-hypotonic facies syndrome (MRXHF1) is also caused by mutation in the ATRX gene. MRXHF1 comprises several syndromes previously reported separately. These include Juberg-Marsidi, Carpenter-Waziri, Holmes-Gang, and Smith-Fineman-Myers syndromes. See also H00228 Thalassemia and H00577 Syndromic X-linked mental retardation.
Non-skewed X-inactivation may cause mental retardation in a female carrier of X-linked alpha-thalassemia/mental retardation syndrome (ATR-X): X-inactivation study of nine female carriers of ATR-X.
