New mutations and sporadic intellectual disability

摘要

Intellectual disability is a worldwide health problem and causes a substantial socioeconomic burden, mostly for families.1 It is common, affecting around 1 in 75 children by the age of 10 years, and boys are affected more often than are girls (in a 1-6:1 ratio). About two-thirds of patients are mildly affected (intelligence quotient 50-70), and a third are severely affected (intelligence quotient <50). Intellectual disability is highly heterogeneous; genetic and environmental factors and chance events during development and early life all contribute. Chromosome abnormalities (eg, Down's syndrome and chromosome rearrangements) and single gene disorders (eg, fragile X syndrome) are the main genetic causes-the total number of genome-wide loci for intellectual disability is probably in the thousands.