An X-linked syndromic intellectual disability that that includes subtypes of the heterogeneous, eponymously named Lujan-Fryns syndrome, X-linked Ohdo syndrome, and Optiz-Kaveggia/ FG syndrome, which is caused by mutations in the gene MED12. The common and most penetrant phenotype shared amongst these disease entities is intellectual disability, with dysgenesis or agenesis of the corpus callosum, blepharophimosis, and marfanoid habitus having variable phenotypic expressivity.