Key results from this study include: a significant enrichment of de novo mutations in MED13 within ID/DD cohorts (p = 0.00371); the clustering and conservation levels of the positions affected by the observed missense variation (Fig. 2a, b); the computationally predicted deleteriousness of the observed mutations (Table 1; Fig. 3, Supplementary Fig. 1); and the overlap of phenotypic features among the 13 patients presented here, including speech difficulties (13/13), intellectual disability (at least 9/13), and eye or vision problems (8/13). This evidence concerns the gene MED13 and Intellectual disability.