EHMT1 and Kleefstra syndrome: One of the most well-known disorders associated with EHMT1 mutations is Kleefstra syndrome (KS; OMIM 610253), a rare genetic condition characterized by intellectual disability (ID), childhood hypotonia, and distinctive facial features (Kleefstra et al., 2006; Kleefstra et al., 2005; Kleefstra et al., 2012).