Chromosomal aberrations in 85 mentally retarded patients examined by high resolution banding.

Eighty-five mentally retarded patients had their chromosomes examined by using the high resolution banding techniques. Fifty-nine of them had multiple congenital anomalies and/or dysmorphic features. Twenty-six had mental retardation but no major anomalies; they were primarily suspected of having the fragile X syndrome. This suspicion was first excluded. Fifteen patients were found to have a chromosome aberration, interpreted as clinically significant. Eleven of them had been examined earlier by conventional methods. The aberrations found were divided into three groups: (I) those detectable with an accuracy of ca. 300-400 bands (N = 4), (II) those detectable with an accuracy of ca. 400-550 bands (N = 6) and (III) those detectable with an accuracy of ca. 550-850 bands (N = 5). The aberrations are described and discussed.