A cytogenetic survey of 449 patients in a Japanese institution for the mentally retarded

Abstract
A cytogenetic survey was carried out on 449 patients (261 males and 188 females) in an institution for the mentally retarded in Japan. A total of 37 patients (8.1%) had chromosome abnormalities. There were 33 individuals (7.3%) with trisomy 21. One patient with 46, XY/47, XY,+12p, 1 with 46, XY, r(22) and 1 with 45, XY,-13,-14,+t(13q14q) were also found. Only 1 female had an abnormal sex chromosome constitution, 47, XXX. The significant contribution of chromosome abnormalities in the etiology of mental retardation was discussed. The most common chromosome abnormality was trisomy 21, as seen in other similar surveys.