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Full list of author information is available at the end of the articledelay Background Patients presenting with developmental delay and multiple dysmorphic features are a common diagnostic challenge in the genetics clinic. Over the past decade, many new genetic syndromes have been identified within this area. A signifi-cant number of these have been linked to genes involved in histone modification and chromatin remodeling. These include: Kabuki syndrome types 1 and 2 [MIM:147920 and 300867] [1,2], Kleefstra syndrome [MIM: 610253] [3], KAT6B-related disorders [MIM: 606170 and 603736] [4], Weaver syndrome [MIM: 277590] [5], HDAC8-related dis-orders [MIM:30882 and 309585] [6-8], and Wiedemann-Steiner syndrome [MIM: 605130] [9]. These along with Rubenstein-Taybi [MIM: 180849] [10] and Sotos Syndrome [MIM 117550] [11] make up a broad range of conditions cause by defects in chromatin remodeling genes. Similar to the loss of epigenetic control seen in Rett Syndrome [MIM: 312750], these disorders are thought to result from global changes in gene expression throughout develop