Chromosomal aberrations in the mildly mentally retarded

Abstract

Chromosome analyses were performed un 52 mildly mentally retarded adults and a control group representing the non-retarded population. Chromosomal aberrations were found in 19-2% of the mentally retarded and in 1 9% of the controls. The aberrations in the retarded group consisted of trisomy 21, fragile-X, sexchromosome aberrations and balanced translocations. The Index group included a man with a fragile site Xp22.1. The aberration in the control group consisted of a karyotype with an extra marker chromosome.

Clinical psychologists' attitudes towards the biology and ‘new genetics’ of intellectual and developmental disabilities: a pilot study using Q‐methodology

“…Also, genetic causes of mild and moderate IDD can be identified, whereas traditionally, this degree of IDD was thought to have an environmental cause (Gostason et al . ; Matalainen et al . ; Rutter et al .…”

“…As current genetic technology also allows for the identification and elucidation of many new syndromes, the proportion of unknown aetiology in intellectual and developmental disabilities (IDD) continues to reduce. Also, genetic causes of mild and moderate IDD can be identified, whereas traditionally, this degree of IDD was thought to have an environmental cause (Gostason et al 1991;Matalainen et al 1995;Rutter et al 1996). These identifications are supported by research on de novo mutations, where neither parent possesses or transmits the mutation leading to an IDD (Vissers et al 2010;Veltman & Brunner 2012;Ellison et al 2013).…”

Children with learning disabilities

“…The causes of learning disability are numerous and can be attributed to either genetic or environmental factors affecting neurodevelopment [see Table 2 (7–9)]; 40–80% of children with a learning disability have no identifiable cause (7,10,11). The commonest identifiable cause is a chromosomal aberration particularly in children with severe learning difficulties although 19% of children with mild learning difficulties also do (12). Mild learning difficulties have a much higher association with low socioeconomic class and are less likely to have a clearly identifiable cause (9,13).…”

Scope for more genetic testing in learning disability

“…The incidence of chromosomal abnormalities has consistently been found to be higher in people with mild learning disability than the general population. Gostason et al (1991) found chromosomal aberrations in 19.2% of a sample of 57 people with mild learning disability compared with 1.9% of controls. It may be that many cases of mild disability are not owing to a culmination of polygenic inheritance and environment, but rather because of genetic defects of the X-chromosome which can be small and not necessarily associated with other obvious dysmorphology.…”