Intellectual disability (ID) is a lifelong disability that presents in infancy or the early childhood years and is typically measured in three domains: intelligence (IQ), adaptive behavior and systems of support. Non-syndromic ID refers to the presence of ID without accompanying additional physical, neurological, and/or metabolic abnormalities. The prevalence of ID (syndromic and non-syndromic) is estimated to be between 1% - 3%. In general, there is wide variation in the causes of ID: 18 – 44% of cases have exogenous causes (like teratogen exposure or infection) and 17 – 47% have genetic causes. X-linked ID affects between 1/600-1/1000 males and a substantial number of females. The etiology remains unknown in up to 80% of cases with mild intellectual disability. Depending on the underlying etiology, the recurrence risk can vary between the background and 50%.
The distinction between syndromic and non-syndromic ID is not precise. Conditions previously regarded as non-syndromic forms of ID may have additional clinical findings that were not intially recognized or emphasized, thus a range of mutations in a single gene can sometimes confer both syndromic and non-syndromic phenotypes. Our ‘non-specific’ ID panels include mainly non-syndromic forms of ID, but also include many syndromic forms of ID to account for the above. This panel includes sequence and deletion/duplication analysis of all the listed genes.
