An etiological survey of the severely retarded Hertfordshire children who were born between January 1, 1965 and December 31, 1967

Abstract

An etiological survey is presented of all suveryl retarded children living in Hertfordshire, at home and in residential care, born between January 1, 1965, and December 31, 1967. One hundred and forty-six children (87 boys and 59 girls) were ascertained, out of a total population of 46,960, with a prevalence of 1 in 320 or 3.1 per 1,000. Approximately 1/3 (47) had the Down syndrome, 1 per 1,000 population. It was possible to establish a diagnosis in a further 45 cases, which included 1 additional case of autosomal chromosome abnormality and 7 each of autosomal dominant, recessive and X-linked conditions; 17 were associated with presumed multifactorial etiological factors; in 6 the condition was thought to have been caused by an environmental agent. It was not possible to establish a cause in the remaining 54 cases. Recurrence risks of severe mental retardation in cases where it is possible to establish a definite diagnosis are discussed and the potential value, for genetic counseling purposes, of a categorizing such patients into broad symptomatological groups, is suggested.

Chromosomal investigations in patients with mental retardation and/or congenital malformations

“…With this approach, a definitive diagnosis for a chromosomal disorder was recorded in 28.6% of the patients with mental retardation and/or congenital malformations. The frequency of chromosomal anomalies was higher than that found by Fryns et al (1986) (15.03%), Dereymaeker et al (1988) (13.3%) and Fryns et al (1990) (17.6%), but lower than that observed in two other studies (Gustavson et al, 1977;Laxova et al, 1977): 32 and 32.2%, respectively. The differences in the frequencies of chromosomal abnormalities among these studies are probably due to variations in the criteria for inclusion of patients and the cytogenetic methodology applied.…”

X-linked mental retardation syndrome with short stature, small hands and feet, seizures, cleft palate, and glaucoma is linked to Xq28

“…For mutant genes on the X chromosome to account for an overall excess of 30% males, such mutations would cause approximately 1 in 7 cases of mental retardation. A frequency of this magnitude (∼15% of all cases of mental retardation) has not been found in major surveys of mental retardation [Anderson et al, 1996;Hunter et al, 1980;Gustavson et al, 1977;Laxova et al, 1977;Kaveggia et al, 1975;Moser and Wolf, 1971]. These surveys report less than 5% of cases representing XLMR.…”

Diagnostic investigations in individuals with mental retardation: a systematic literature review of their usefulness

“…This was reported in 10 studies. 59,63,65,80,92,99,106,113,114 The median number of families in which relatives with MR were present was 15.0% (range 7.5 -46%). However, it was generally not stated to which extent the family was surveyed for MR nor to which extent it was reported in the publication.…”