The contribution of X-linked coding variation to severe developmental disorders

Over 130 X-linked genes have been robustly associated with developmental disorders (DDs), and X-linked causes have been hypothesised to underlie the higher DD rates in males. We evaluated the burden of X-linked coding variation in 11,046 DD patients, and found a similar rate of X-linked causes in males and females (6.0% and 6.9%, respectively), indicating that such variants do not account for the 1.4-fold male bias. We developed an improved strategy to detect novel X-linked DDs and identified 23 significant genes, all of which were previously known, consistent with our inference that the vast majority of the X-linked burden is in known DD-associated genes. Importantly, we estimated that, in male probands, only 13% of inherited rare missense variants in known DD-associated genes are likely to be pathogenic. Our results demonstrate that statistical analysis of large datasets can refine our understanding of modes of inheritance for individual X-linked disorders.