right hemisphere rather than decrease on the left. Although decreased volume in white matter was not as commonly found as in gray matter, the thinner corpus callosum in 49,XXXXY, decreased FA in 47,XXY, and X-chromosome dosage-related increases in white matter hyperintensities suggest supernumerary X-chromosomes have a significant impact on white matter development as well. This appears severe enough in individuals with pentasomy or tetrasomy that it has been suggested these disorders be included in the differential diagnosis for leukoencephalopathy [Garcia-Cazorla et al., 2004; Hoffman et al., 2008].
