XXXY, XXXXY, XXYY /thrē′ekswī, fôr′ekswī, dob′əleks′-dob′əlwī′/ , the designations for abnormal sex chromosome complements in the human male in which there are more than the normal one X and one Y chromosome, resulting in a total of 48, 49, or more chromosomes in each somatic cell. The aberration is a variant of Klinefelter’s syndrome. In general, the more X chromosomes there are, the greater the number of congenital defects and the severity of intellectual disability in the affected individual. See also Klinefelter’s syndrome.
