DNMT3A and Heyn-Sproul-Jackson syndrome: In contrast, gain-of-function (GoF) variants of DNMT3A were shown to cause Heyn-Sproul-Jackson syndrome (HESJAS; OMIM #618724), a very rare condition reported in only three patients to date, all of whom presented with microcephalic primordial dwarfism (Heyn et al., 2019).