Mild intellectual deficits in a child with 49,XXXXY

Severe mental retardation usually is present in males with a 49,XXXXY karyotype, although occasionally, intellectual functioning has been reported to be in the mild range of mental retardation. One child was previously described to have normal development at 15 months, but had mental retardation at 41 months. We present a male with 49,XXXXY who had mild-cognitive and motor delays and age-appropriate adaptive skills at 59 months. Greatest deficits were in expressive verbalizations similar to other male sex chromosome abnormalities. Mosaicism could not be demonstrated in blood or skin specimens. Although most males with 49,XXXXY syndrome will have significant mental retardation, findings in our patient and other reports suggest that variability in intellectual functioning may occur, in some instances, and may justify guarded optimism in affected males demonstrating close to or age-appropriate developmental skills through early childhood.