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Common diseases are very often complex because they are genetically heterogeneous, with different genetic defects that give rise to clinically indistinguishable phenotypes. This phenomenon has been documented for early-onset cognitive impairment. Intellectual disability (ID) affects 2.5% of the population worldwide (Mol Genet Metab 2012; 105:368), and de novo mutations represent an important cause.
In this study, researchers performed whole-exome sequencing on blood samples obtained from 47 individuals with ID. Six patients were excluded; the remaining 41 probands had been born to predominantly nonconsanguineous parents of European origin. Among 37 probands, the researchers found variants in 2 genes newly implicated in diseases, 9 new candid…