A specific syndrome due to deletion of the distal long arm of chromosome 1.

We have studied 2 patients with de novo deletion 1 (q42.3----qter): a 5 1/2-year-old boy and an unrelated 1 9/12-year-old girl. The analysis of the phenotype which is now possible in a total of 23 cases shows that the deletion of the terminal 1q leads to a definable multiple congenital anomalies/mental retardation (MCA/MR) syndrome. The phenotype is so characteristic that, as a rule, the clinical data should suggest the correct cytogenetic diagnosis.