The bromodomain and WD repeat domain containing 3 gene (BRWD3) encodes a predominantly uncharacterized protein that has been implicated in the JAK/STAT-signaling pathway. The BRWD3 gene is located at Xq21.1 and contains 41 coding exons. Missense and splicing mutations, as well as a small insertion, in the BRWD3 gene have been reported in patients with X-linked mental retardation (Field M et al. Am J Hum Genet. 2007;81:367-374).