X-linked intellectual disability
X-linked mental retardation refers to medical disorders associated with X-linked recessive inheritance that result in intellectual disability. As with most X-linked disorders, males are more heavily affected than females. Females with one affected X chromosome and one normal X chromosome tend to have milder symptoms. Unlike many other types of intellectual disability, the genetics of these conditions are relatively well understood. It has been estimated there are ~200 genes involved in this syndrome; of these ~100 have been identified. Many of these genes are found on the short 'p' arm of the chromosome , and duplications at Xp11.2 are associated with the syndromic form of the condition. X-linked mental retardation accounts for ~16% of all cases of intellectual disability in males. Syndromes. Several X-linked syndromes include intellectual disability as part of the presentation. These include: List of genes. Following is a list of genes located on the X chromosome and linked to intellectual disability. There are also several loci that have not been associated with a specific gene.