Chromosome abnormalities in pupils attending ESN/M schools

Array CGH Analysis and Developmental Delay: A Diagnostic Tool for Neurologists

Developmental delay occurs in 1-3% of the population, with unknown etiology in approximately 50% of cases. Initial genetic work up for developmental delay previously included chromosome analysis and subtelomeric FISH (fluorescent in situ hybridization). Array Comparative Genomic Hybridization (aCGH) has emerged as a tool to detect genetic copy number changes and uniparental disomy and is the most sensitive test in providing etiological diagnosis in developmental delay. aCGH allows for the provision of prognosis and recurrence risks, improves access to resources, helps limit further investigations and may alter medical management in many cases. aCGH has led to the delineation of novel genetic syndromes associated with developmental delay. An illustrative case of a 31-year-old man with long standing global developmental delay and recently diagnosed 4q21 deletion syndrome with a deletion of 20.8 Mb genomic interval is provided. aCGH is now recommended as a first line test in children and adults with undiagnosed developmental delay and congenital anomalies.

Puce d'hybridation génomique comparative et retard de développement : un outil diagnostic pour les neurologues. Le retard de développement survient chez 1 à 3% de la population et son étiologie est inconnue chez à peu près 50% des cas. L'évaluation génétique initiale pour un retard de développement incluait antérieurement une analyse chromosomique et une analyse par FISH (hybridation in situ en fluorescence) de régions subtélomériques. La puce d'hybridation génomique comparative (CGHa) est devenue un outil de détection des changements du nombre de copies géniques ainsi que de la disomie uniparentale et elle est le test le plus sensible pour fournir un diagnostic étiologique dans le retard de développement. Le CGHa permet d'offrir un pronostic et un risque de récurrence, améliore l'accès aux ressources, aide à limiter les évaluations et peut modifier le traitement médical dans bien des cas. Le CGHa a mené à la définition de nouveaux syndromes génétiques associés à un retard de développement. À titre d'exemple, nous décrivons le cas d'un homme âgé de 31 ans qui présentait un retard de développement global depuis longtemps et chez qui un syndrome associé à une délétion 4q21 a été diagnostiqué récemment, soit une délétion de 20,8 Mb. Le CGHa est maintenant recommandé comme test de première ligne chez les enfants et les adultes présentant un retard de développement et des anomalies congénitales.

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

There are no guidelines available for diagnostic studies in patients with mental retardation (MR) established in an evidence-based manner. Here we report such study, based on information from original studies on the results with respect to detected significant anomalies (yield) of six major diagnostic investigations, and evaluate whether the yield differs depending on setting, MR severity, and gender. Results for cytogenetic studies showed the mean yield of chromosome aberrations in classical cytogenetics to be 9.5% (variation: 5.4% in school populations to 13.3% in institute populations; 4.1% in borderline-mild MR to 13.3% in moderate-profound MR; more frequent structural anomalies in females). The median yield of subtelomeric studies was 4.4% (also showing female predominance). For fragile X screening, yields were 5.4% (cytogenetic studies) and 2.0% (molecular studies) (higher yield in moderate-profound MR; checklist use useful). In metabolic investigations, the mean yield of all studies was 1.0% (results depending on neonatal screening programmes; in individual populations higher yield for specific metabolic disorders). Studies on neurological examination all showed a high yield (mean 42.9%; irrespective of setting, degree of MR, and gender). The yield of neuroimaging studies for abnormalities was 30.0% (higher yield if performed on an indicated basis) and the yield for finding a diagnosis based on neuroradiological studies only was 1.3% (no data available on value of negative findings). A very high yield was found for dysmorphologic examination (variation 39-81%). The data from this review allow conclusions for most types of diagnostic investigations in MR patients. Recommendations for further studies are provided.

Fragile-X syndrome in North East Essex: towards systematic screening: clinical selection

A systematic screening for fragile-X syndrome, using various clinical criteria to preselect for cytogenetic testing, was performed throughout the North East Essex Health District on 1100 people attending three different local services for people with learning disability. The selection procedure used varied from a gestalt impression to head, ear and testis measurement depending on the setting. Fifty-nine males and five females who met the selection criteria went on to have chromosome studies. Of these, 23 males and one female were positive (more than 4% positive cells). They came from 19 families. Whilst the true prevalence of fragile-X syndrome is not known in the district, at a minimum, it contributed 3.2% of the institutionalized males (health authority care), 4.4% of the boys and 2.1% of the girls attending special schools for severe learning disability, 7.9% of the boys attending schools for mild learning disability (Local Education Authority), and 3.5% of men attending the two adult training centres within the district (social services). These figures compare well with the yield from reported surveys in which all individuals without a known diagnosis were tested cytogenetically.

Attitudes of the mildly mentally retarded children's parents toward their children's handicap: Dammam - Saudi Arabia

The objectives of this case-control study was to identify the attitudes of parents of mentally retarded children towards the illness of their children. Sixty-nine parents ofrniltlly mentally retarded male children (MR group) and a similar number of matched parents of normal male children (Control Group) were interviewed using a questionnaire.The parents of the MR group had feelings of guilt and self-blame which was significantly higher in mothers than in fathers. Feeling of rejection and inferiority were reported by the parents with no significant difference between fathers and mothers. All of the rates, however, were found to be less than those reported /tom western societies. Failure of families to investigate causes of mental retardation was found in more than a quarter of all the study groups. Parents of the MR group asked for more services to be provided by the appropriate governmental agencies.

Survey of adolescents with severe intellectual handicap

A diagnostic survey was undertaken of children aged 11 to 19 years in Tameside with severe learning difficulties (intelligence quotient less than or equal to 50). Eighty-two children were identified and their medical records reviewed. A specific diagnosis for the retardation was documented in 25 (30%) of the children, 18 of whom had Down's syndrome. A probable aetiology or a disorder of unknown aetiology had been identified in a further 21 (26%) children. To confirm the existing diagnosis, identify new diagnoses, and offer genetic counselling, the parents of 63 children were offered detailed reassessment of their child. Fifty three children were reviewed, and a specific disorder identified in 25 out of 31 previously undiagnosed children. The most frequent diagnoses made were fragile X syndrome and Rett's syndrome. On completion of the survey, 61 of the 82 children (74%) had a specific diagnosis or probable aetiology identified, 12 (15%) had associated disorders such as cerebral palsy, and in only nine of the 82 children (11%) were there no clues at all to the cause of their retardation.

Aetiology of mild mental retardation

A clinical and family study was carried out in 169 children attending schools for the mildly mentally retarded in Southampton to assess the prevalence of recognised medical risk factors; 71 children (42%) had such risk factors. These were prenatal in 22, perinatal in 41, and postnatal in eight. Risk factors of possible, but less certain, significance were found in a further 63 children (37%). In 86 families (51%) there was a history of serious educational problems in both parents. The prevalence of both types of risk factor was higher in the children whose parents had no educational problems. There were, however, 25 children (15%) whose parents had no history of educational problems and in whom medical risk factors were either absent or minimal.

Children with the fragile X chromosome at schools for the mildly mentally retarded

An investigation of children in schools for the moderately mentally handicapped in Coventry demonstrated that 29 of 259 children had a significant chromosomal abnormality. 10 of 155 boys (6 per cent) and 10 of 104 girls (10 per cent) had the fragile X syndrome. The clinical features which suggested this syndrome in males were IQ in the 50 to 70 range, head circumference greater than the 50th centile and post-pubertal testicular volume greater than the 50th centile. For both males and females, large ears were a useful sign. All children with fragile X had a carrier parent. The occurrence of mental retardation among sibs was one in two for brothers and one in four sisters. Considering all the males with fragile X syndrome resident in Coventry (this and previous studies), there were twice as many in schools for the moderately mentally handicapped as there were in schools for the severely mentally handicapped. There were as many females as males in the schools for the moderately mentally handicapped.