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). This evidence concerns the gene DNMT3A and isolated growth hormone deficiency type IA.