Chromosomal abnormalities in child psychiatric patients

To determine the frequency of chromosomal abnormalities in a child psychiat ric population, and to evaluate possible associations between types of abno rmalities and patient's clinical characteristics, cytogenetic examination w as performed on 604 patients. Demographic data, reasons for karyotyping, cl inical signs, and other patient characteristics were assessed and correlate d with the results from karyotyping, Chromosomal abnormalities were found i n 69 patients (11.3%); these were structural in 49 cases and numerical in 2 0, Inversion of chromosome nine was found in 15 subjects, trisomy of chromo some 21 in 11, and fragile X in five patients. When karyotyping was perform ed because of intellectual impairment or multiple developmental delay, sign ificantly more abnormalities were found than average; when performed becaus e autistic disorder was suspected, the number of abnormalities was signific antly fewer, There were no differences in clinical variables between struct ural and numerical abnormalities, nor among nine types of chromosomal abnor malities, except that numerical abnormalities and polymorphism were found a t a later age, and that walking was more delayed and IQ was lower in patien ts with Down syndrome. Clinicians should be aware of the possible presence of chromosomal abnormalities in child psychiatric populations; the close co llaboration with geneticists and the use of more defined guidelines for cyt ogenetic investigation are important.