The recognition and investigation of X-linked learning disability syndromes.

X-linked learning disability syndromes occur in approximately one per 600 live male births and account for 20-30% of all learning disability. Fragile-X syndrome comprises some 40% of all X-linked learning disability, and there are currently about 95 recognized syndromes comprising the rest. Clinicians should be alert to these other forms of X-linked learning disability: families should be offered genetic counselling, including dysmorphology opinion and cytogenetic testing. Gene mapping on the X chromosome is advancing very rapidly and some causative genes for X-linked learning disability are now known. Clinicians involved in the care of patients with X-linked learning disability are encouraged to investigate all families, report new syndromes and those with cytogenetic abnormalities, and collaborate with clinical geneticists and laboratory scientists working on X chromosome gene mapping.