Alpha thalassaemia / mental retardation (ATR- 16) syndrome

alpha-thalassemia/mental retardation (ATR) syndromes (ATR-16 Syndrome)

• this condition is also one where mental retardation is found in children with alpha thalassemia (1)
• associated with deletion of part of chromosome 16 short-arm (16p) telomere (1)
• associated with varied phenotype of other developmental abnormalities (1)
• in some, the chromosomal abnormalities can be visualized by cytogenetic analysis or fluorescent in situ hybridization (FISH)
  • in most cases, one parent carried a balanced translocation that the child inherited in an unbalanced fashion. In others, the abnormality arose as de novo events. If the affected child also inherited a common single alpha globin gene deletion from the other parent, the child would have Hb H disease

Notes:

• thought that mental retardation and other congenital anomalies observed in this syndrome are caused by the deletion of dosage-sensitive genes on one 16p telomere and other concomitant chromosomal abnormalities
• ATR-X syndrome
  • this syndrome is an X-linked disorder, caused by mutations of theATRX gene located on chromosome Xq13.3

Reference:

• (1) David H. K. Chui, Suthat Fucharoen, and Vivian Chan, S, 2003. Hemoglobin H disease: not necessarily a benign disorder. Blood, 101 (3), 791-800