[Cytogenetic study of 350 mental deficient patients at medico-pedagogic institutions].

This report brings to light the results of cytogenetic study carried out on 350 mentally retarded persons (medium: Group I, deep Group II). In 8,2% and 12,56% of the cases a chromosomic abnormality is observed (mainly trisomy 21). These percentages are in correlation with the results of other studies. Ante and peri natal pathology plays a very important part among exogenous factors. In numerous cases a multifactors etiology can be found as the cause of this mental retardation, the effect of an initial organic mental retardation being aggravated by precocious affective perturbations. For those cases without apparent etiology, a teratologic origin may be thought as their cause.