Klinefelter's ciwo wani yanayi ne na kwayoyin halitta wanda ke shafar maza. Ana haifar da shi ta hanyar ƙarin kwafin chromosome na X, wanda ke haifar da genotype na XXY maimakon XY na yau da kullun. Wannan na iya haifar da bambance-bambance na zahiri, ci gaba, da ɗabi'a, gami da rage yawan haihuwa, ƙananan gwanaye, da ƙara girman ƙirji. Hakanan yana iya haɗawa da ilmantarwa da matsalolin zamantakewa, da kuma ƙara haɗarin wasu matsalolin kiwon lafiya kamar osteoporosis da cututtukan autoimmune. Jiyya na iya haɗawa da maganin hormone, magana da aikin aikin likita, da tallafin tunani.