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.

    91/100 (page 77)
    GENERAL DISCUSSION 77 to the preponderance of male patients is discussed later. A similar trend is noted by Davison (see Part i) who found an excess of males with mental defect in 190 families with two or more affected members. The excess was most marked in those who were severely affected. In the present series severe growth retardation of more than 3*5 S.D. below the mean for normal children of the same age is largely confined to males. Ten subjects who have heights which are 4 S.D. or more below the mean are all males (Fig. 1). It appears, therefore, that disorders detected by the criteria for inclusion in the survey may cause greater growth retarda¬ tion in males than females. The I.Q,.s of patients in Group С (that is of individuals with no evidence of hereditary disorder other than family history) range from 15 to 60 with a mean of 38*6. The I.Q.s of patients in Groups D and E range from 15 to 60 and have a mean of 30-3. These last two groups contain subjects who have biochemical or clinical evidence of disorder in addition to familial involvement. In two families (families 3, 11) the clinical features of the mothers were sufficiently similar to those of the propositi to suggest that inheri¬ tance was probably of the dominant variety. However, because of insufficient data an auto¬ somal recessive form of inheritance could not be excluded. Autosomal recessive form of inheritance was consistent with the genetic data of the majority of our families, but was asserted with greater confidence in families (a) when there was parental consanguinity (families 8, 12, 19, 27, 28) and (b) in families in which the affected siblings had an identical metabolic abnormality which was not present in their parents and in which X-linked inheritance could be excluded (families 3, 5,^ 7, 22, 25). The possibility that inheritance was of the X-linked recessive type (or sex-limited as an added possibility) was considered when only (0 Ф CO Ü Ц-< о и ф д s э -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 О +1 Standard deviations Fig. i.—Distribution of heights according to standard deviations from the mean of normal subjects of same age and sex (normal data from Tanner ei rt/., 1966).