The role of RET genomic variants in infantile hypertrophic pyloric stenosis.

Infantile hypertrophic pyloric stenosis (IHPS) is a common childhood pathology affecting approximately 1-5 children pro 1000 newborns, with a genetic background as suggested by the familial occurrence. RET is a candidate gene for IHPS due to its role in the development of the intrinsic innervation and ganglia of the smooth musculature and the association of RET variants with another motility disorder (Hirschsprung's disease). Accordingly, we investigated RET-IHPS associations through sequencing of the complete RET coding region in 32 IHPS patients. Genotype frequencies were compared between patients and 48 controls using the Cochran-Armitage trend test or Fischer's test for exact p-values. We found 19 RET variants in IHPS, including polymorphisms in the promoter region (c.-200 G>A and c.-196 C>A). There was no statistically significant difference between the frequencies of the variants in both groups. There was no deviation from the Hardy-Weinberg equilibrium, yet a significant correlation (linkage disequilibrium) for variants in the promoter region, in exons 11, 13, 14 and 19 and in the 3' UTR. We conclude that RET variants are present in IHPS patients yet show no significant statistical association with the IHPS phenotype, suggesting at best an adjuvant role for RET in IHPS.

Working memory functions in children with different degrees of intellectual disability.

BACKGROUND: In recent years, there has been increased research interest in the functioning of working memory in people with intellectual disabilities. Although studies have repeatedly found these individuals to have weak working memory skills, few investigations have distinguished between different degrees of intellectual disability. This study aims to help close this research gap and, in so doing, to examine whether the deficits observed reflect a developmental lag or a qualitative deviation from normal development. METHOD: In a 5-group design, the working memory performance of a group of 15-year-olds with mild intellectual disability (IQ 50-69) was compared with that of two groups of children (aged 10 and 15 years) with borderline intellectual disability (IQ 70-84) and with that of two groups of children with average intellectual abilities (IQ 90-115) matched for mental and chronological age (aged 7 and 15 years). All children were administered a comprehensive battery of tests assessing the central executive, the visual-spatial sketchpad, and the phonological loop. RESULTS: The results showed deficits in all three components of working memory, and revealed that these deficits increased with the degree of intellectual disability. The findings indicate that, relative to their mental age peers, children with learning difficulties show structural abnormalities in the phonological store of the phonological loop, but developmental lags in the other two subsystems. CONCLUSIONS: Similar patterns of results emerged for both subgroups of children with intellectual disability, indicating that problems with phonological information processing seem to be one of the causes of cognitive impairment in individuals with intellectual disability.

Working memory functioning in children with learning disabilities: does intelligence make a difference?

BACKGROUND: Children with learning disabilities are identified by their severe learning problems and their deficient school achievement. On the other hand, children with sub-average school achievement and sub-average intellectual development are thought to suffer from a general intellectual delay rather than from specific learning disabilities. The open question is whether these two groups are characterised by differences in their cognitive functioning. The present study explored several functions of working memory. METHOD: A working memory battery with tasks for the phonological loop, the visual-spatial sketchpad and central executive skills was presented in individual sessions to 27 children with learning disabilities and normal IQ (ICD-10: mixed disorders of scholastic skills), 27 children with learning disabilities and low IQ (intellectual disabilities), and a control group of 27 typically developing children with regular school achievement levels and normal IQ. RESULTS: The results reveal an overall deficit in working memory of the two groups with learning disabilities compared with the control group. However, unexpectedly, there were no differences between the two groups of children with disabilities (normal vs. low IQ). CONCLUSIONS: These findings do not support the notion of different cognitive functioning because of differences in intelligence of these two groups. In the ongoing discussion about the role of intelligence (especially as to the postulated discrepancy between intelligence and school achievement in diagnosis and special education), our findings might lead to rethinking the current practice of treating these two groups as fundamentally different.