Here we report the 19th case of MKMS, a 10-year-old male patient with a hemizygous missense STAG2 variant (GRCh37/hg19: chrX:123179026, c.475T>C, p.Tyr159His; NC_000023.11:g.124045176T>C) with previously unreported clinical features that expand the known manifestation of the disorder. This evidence concerns the gene STAG2 and Mullegama-Klein-Martinez syndrome.