Diagnostic approach to the etiology of mental retardation.

The clinical and laboratory investigation of the etiology of mental retardation is discussed. By clinically determining the stage of onset of the mental retardation, it is possible to dispense with a large number of special investigations. It is concluded that the laboratory is chiefly of value in confirming clinical suspicions, and that only rarely will random or routine testing yield an unexpected diagnosis. The possible exception is dermatoglyphic analysis in nondysmorphic, idiopathically retarded patients. This examination demonstrated probable antenatal causative factors in a high percentage of children with retardation of intrauterine origin. If further investigation were to confirm the findings, then this simple examination should be included in the routine evaluation of these cases.