X-Linked mental retardation

X-Linked mental retardation refers to forms of mental retardation which are specifically associated with the X chromosome.

Unlike many other types of mental retardation, the genetics of these conditions are relatively well understood.

As with most X-linked disorders, males are more heavily affected than females. Females with one affected X and one normal X tend to have milder symptoms.

This form of intellectual disability accounts for ~16% of all cases in males. It has been estimated there are ~200 genes involved in this syndrome; of these ~100 have been identified.

Types
Types include:

There are also several loci that have not been associated with a specific gene.

Several X-linked syndromes include retardation as part of the presentation. These include Coffin-Lowry syndrome, MASA syndrome, and X-linked alpha thalassemia mental retardation syndrome.