Annotation: fragile X syndrome: advances and controversy

Personality traits in parents of people with autism

Objectives: This study set out to explore if there were measurable personality characteristics specific to parents of people with autism.

Method: Parents of 12 people with a DSM-III-R diagnosis of autism presented for the study. Each of the people with autism were matched where possible with a counterpart without autism but with a lifelong disability on parameters of age, sex and IQ level. Parents of the ‘autism’ and ‘non-autism’ groups were then interviewed in detail using four personality assessment instruments. Scores were tabulated for both mothers and fathers in each group and intergroup comparisons were made.

Results: No significant personality profile difference was identifiable between the two parental groups.

Conclusions: Personality traits specific to parents of people with autism are not identifiable in this study thus casting doubt on the validity of personality phenotypes as measurable heritability factors in autism.

Prevalence and phenotype consequence of FRAXA and FRAXE alleles in a large, ethnically diverse, special education-needs population

We conducted a large population-based survey of fragile X (FRAXA) syndrome in ethnically diverse metropolitan Atlanta. The eligible study population consisted of public school children, aged 7-10 years, in special education-needs (SEN) classes. The purpose of the study was to estimate the prevalence among whites and, for the first time, African Americans, among a non-clinically referred population. At present, 5 males with FRAXA syndrome (4 whites and 1 African American), among 1,979 tested males, and no females, among 872 tested females, were identified. All males with FRAXA syndrome were mentally retarded and had been diagnosed previously. The prevalence for FRAXA syndrome was estimated to be 1/3,460 (confidence interval [CI] 1/7,143-1/1,742) for the general white male population and 1/4, 048 (CI 1/16,260-1/1,244) for the general African American male population. We also compared the frequency of intermediate and premutation FRAXA alleles (41-199 repeats) and fragile XE syndrome alleles (31-199 repeats) in the SEN population with that in a control population, to determine if there was a possible phenotype consequence of such high-repeat alleles, as has been reported previously. No difference was observed between our case and control populations, and no difference was observed between populations when the probands were grouped by a rough estimate of IQ based on class placement. These results suggest that there is no phenotype consequence of larger alleles that would cause carriers to be placed in an SEN class.

Influence of depression on cognitive functioning in Fragile X females

We sought to determine the frequency of a history of major depression in women with Fragile X syndrome. In addition, we attempted to disentangle the cognitive effects of major depression from those of Fragile X syndrome. Thirty-seven mothers of developmentally delayed children (Fragile X syndrome: n = 18; comparison group n = 19), matched for age, educational level, and socioeconomic status, were administered psychiatric and neuropsychological measures. Women with Fragile X syndrome had a higher frequency of lifetime diagnosis of major depressive disorder (78%) than the comparison group (37%). Mild impairment was seen on visuospatial construction and memory tasks in women with Fragile X syndrome, while women with depression showed subtle deficits in several aspects of visuospatial perception and learning. There was no interaction of Fragile X syndrome and depression in their influence on cognition. The results underscore the importance of considering the influence of depression on cognitive performance in studies of genetic disorders.

Annotation: behavioural phenotypes: a window onto the biology of behaviour

Characteristic behavioural patterns (including cognitive processes and social interactions) have been reported in a number of syndromes arising from genetic or chromosomal abnormalities, suggesting that molecular analysis of the underlying defect could reveal the biological basis of the behavioural phenotype. Because of the rarity of many of the syndromes, and the complexity of their genetic basis, there are great difficulties in establishing the validity of the association between syndrome and behavioural phenotype. Nevertheless, evidence from animal studies with relevance to human behavioural phenotypes shows that the pathway from genotype to phenotype may be accessible by careful delineation of behavioural phenotypes.

Apparently enhanced visual information processing in female fragile X carriers: preliminary findings

Eighteen normally intelligent adult female fragile X carriers were tested with the "de Sonneville Visual Attention Tasks," a computer-based set of reaction-time experiments, in order to assess different aspects of their attention capacity. The subject group was compared with a group of 48 adults, who were not known to be fragile X carriers. We publish preliminary results of this study. These show that the fragile X carriers have significantly faster reaction times at a substantial number of the tests. This suggests that normally intelligent female fragile X carriers might process simple visual information, such as the targets offered in these reaction time experiments, at a faster rate than control women.

Fragile X (Martin-Bell) syndrome

Fragile X syndrome is a common condition resulting from a cytogenetic abnormality in the X chromosome. Mental retardation, characteristic facies, and large testes are some of the most important characteristics of the condition. The relatively high incidence of the syndrome--approximately one per thousand--the high incidence of cardiac anomalies in these individuals, the oral and facial features associated with the condition, and the paucity of reported cases in the dental literature make it particularly interesting to dentistry. Here we report the case of a 12-year-old male, including the cytogenetic and cephalometric analyses, presenting with some of the classic features and some features not commonly reported.