Chromosomal investigations in patients with mental retardation and/or congenital malformations

We investigated the chromosomal constitution of patients with mental retard ation and/or congenital malformations in order to determine genetic causes for such disturbances, The GTG and CBG banding patterns were studied using phytohemagglutinin M-stimulated lymphocytes cultured from peripheral blood. Among 98 individuals with mental retardation and/or congenital malformatio ns who were analyzed there were 12 cases of Down's syndrome, two of Edward' s syndrome, one of Patau's syndrome, five of Turner's syndrome, two of Klin efelter's syndrome, one of "cri-du-chat" syndrome, one case of a balanced t ranslocation between chromosomes 13 and 14, one case of a derivative chromo some and one of a marker chromosome. We found abnormal chromosomes in 26% o f the patients, 82% of which were numerical abnormalities, with the remaini ng 18% being structural variants. We conclude that patients with mental ret ardation and/or congenital malformations should be routinely karyotyped.