Genetic studies in mental subnormality.

Date:
1973
Catalogue details

Licence: Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)

Credit: Genetic studies in mental subnormality. Source: Wellcome Collection.

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    6 GENETIC STUDIES IN MENTAL SUBNORMALITY where environmental factors seemed to be the cause of the severe mental retardation. Sum¬ marized information on these families is given in Table I (see also Fig. 3 placed at end of Section I), and further details are set out in Appendix I. Neither clinical nor laboratory findings suggested that the affected members in the remaining 141 families were suffering from known traits, although, as will be discussed later, there were in some families similarities between affected members. No new cases of a metabolic disorder were found on urinalysis. It is difficult to assess the significance of these mild excess acidurias as there are few available data •on prevalences in normal populations. Studies have been made of variations of levels of amino acids in mental defectives and compared with normal controls. However, techniques vary in the levels of thresholds of detection of amino acids and qualitative techniques do not yield sufficiently exact or comparable findings. The findings are not incompatible with those reported by other authors (e.g. Wright, Shaw, Roth, Traub and Johnson, 1961, Carson and Neill, 1962 ; and Poser and Bunch, 1963). The patients with these mild abnormal urine findings will subsequently be considered as having idiopathic mental defect. Mental defect associated with epilepsy was one of the diagnoses used by Penrose (1938) in his clinical analysis of mental defect. Since epilepsy is so heterogeneous in origin and is often found in association with physical abnor¬ malities, no attempt was made in the present study to isolate those patients who had epilepsy and those who had epilepsy as well as other physical abnormalities. It is of interest to note that 11 • 8 per cent of the affected individuals either had been or were at the time of examina¬ tion epileptic. In 27 of the families there was a history of epilepsy in other members. This is a lower frequency than has been reported from other surveys, where the frequency ranged from 16 to 24 per cent in institutionalized patients (Penrose, 1938 and Kirman, 1956). Âkesson in 1961, however, only recorded epilepsy in 11 per cent of mental defectives living in a rural area in Sweden, while Tizard and Grad (1961) noted that 18 per cent of severely subnormal children in London were epileptic.