'De novo' trisomy 16q11 to pter.

A de novo 16q- trisomy was found in a patient with severe mental retardation and mild physical abnormalities. A preliminary delineation the clinical features characteristic of trisomy 16q- is proposed, based upon comparison of the two cases identified so far. The mild phenotypical effects of this chromosome imbalance suggest that the alleged lethality of partial chromosome 16 aneuploidies should be reconsidered.