NFIX and Malan overgrowth syndrome: Malan syndrome (MALNS) (MIM 614753) is an ultra-rare genetic disorder (1/1,000,000) caused by heterozygous chromosomal microdeletions involving the 19p13.2 region or loss-of-function (LoF) variants in the NFIX gene (nuclear factor I X) (OMIM 164005) (1).