X-Linked Intellectual Disability: Literature Review

Despite of many extensive studies held on an inielieciual disability, it still reimains one of the most mysterious neuropsychiatric disorders. The prevalence of an intellectual disability (2-3% of the population) and its variability induce active research of the etiology of this disorder. Frequently, such research directs to genetic causes of an intellectual disability. The epidemiology of an intellectual disability is quite astonishing - there are more males, affected by inteliectual dis­ability, than there are females. Such prevalence can explain extensive studies held on the research of X chromosome linked mutations potentially causing intellectual disorders. After reviewing the most significant articles, pubiished during the last 20 years, which investigate the linkage of X chromosome and intellectual disability, it was observed that there was a constant increase of genes, involved in X-linked inteli ectual disability. However, it is very difficult to interpret this result because with a notable improvement of laboratory equipment many genes were identified on other chromosomes, as well. During our research, we anaiysed the ratio between the number of already identified genes, related with intellectual disability on the chromosome and the amount of its protein coding sequences. As predicted, this ratio on X chromosome was 17.12% whereas on other chromosomes the average was 5.4% (p<0.00001). In this review we are presenting a possible causation of such results, several main features of X chromosome and the most frequent and/or exciting examples of X chromosome and intellectual disability linking genetic syndromes.

Hence, there are many syndromes, characterised by X-linked intellectual disability. In this publication their classification and examples are presented. Currently ongoing clinical trials induce hope for patients with intellectual disability and their relatives. However, only when the complete pathogenesis and the function of mutated genes is known, productive studies of effective cure for intellectual disability may begin.