Sex chromosome aneuploidies among men with systemic lupus erythematosus

► Klinefelter's syndrome (male 47,XXY) is associated with SLE. ► Klinefelter's syndrome men have the same rate of SLE as women. ► 46,XX men (de la Chapelle's syndrome) are over-represented among men with SLE. ► 46,XX men have normal levels of sex hormones. ► The sex-bias of SLE is associated with the number of X chromosomes, not sex.