AbstractSubtelomeric imbalances are a frequent cause of cytogenetic abnormalities in patients with unexplained intellectual disability. Functional disomy of Xq28 involving the methyl‐CpG‐binding protein 2 gene (MECP2) has been observed mostly in subtelomeric duplications. We identified three patients with functional disomy of Xq28. A female patient showed an unbalanced translocation between 12q24.33 and Xq28. Two male patients showed an unbalanced translocation between Xq27.1‐ Yq11.22 and a recombinant X‐chromosome containing duplicated material from Xq27.1 on Xp telomere, respectively. All three patients exhibited severe developmental delay, hypotonia, seizures, and distinctive facial features, including flat nasal bridge and hypertelorism. Additionally, brain magnetic resonance imaging (MRI) showed characteristic findings in each patient, including frontal dominant brain atrophy and hypoplasia of the corpus callosum, which are common findings in patients with functional disomies of Xq28 and interstitial duplications of Xq28, including MECP2. Brain MRI revealed a cystic lesion in the periventricular white matter in a patient, similar to our previous experience in patients with MECP2 duplication syndrome. Thus, white matter abnormalities may frequently be seen in cases of patients with additional MECP2 copies. © 2013 Wiley Periodicals, Inc.