Le ʻO ka maʻi maʻi Turner (kapa ʻia i kekahi manawa ka maʻi ʻeha o ka gonadal) he a maʻi maʻi genetika ka mea pili wale i na wahine. ʻO ka mea ʻino e pili ana i kekahi o nā chromosomes X (nā chromosomes sex). Hoʻopilikia ka maʻi Turner ma kahi o 1 i ka 2 mau wahine a ʻike pinepine ʻia i kekahi mau makahiki ma hope o ka hānau ʻana, i ka wā ʻōpio. ʻO nā hōʻailona nui he pōkole pōkole a me ka hana ʻino o nā ovaries. Ua kapa ʻia ʻo Turner syndrome ma muli o ke kauka ʻAmelika nāna i ʻike iā ia ma 1938, ʻo Henri Turner.

Loaʻa i nā kāne he 46 chromosomes me ʻelua mau chromosomes sex i kapa ʻia ʻo XY. ʻO 46 XY ka helu genetic no ke kāne. Loaʻa i nā wāhine he 46 chromosomes me nā chromosomes sex ʻelua i kapa ʻia ʻo 46 XX. No laila, ʻo 46 XX ka helu genetic o ka wahine. I loko o nā wāhine me ka maʻi Turner, aia i loko o ka hui genetic kahi chromosome X hoʻokahi, no laila ʻo ke ʻano genetic o ka wahine me ka maʻi Turner he 45 X0. Ua nele kēia mau wāhine i ka X chromosome a i ʻole ka X chromosome, akā loaʻa kahi mea ʻino i kapa ʻia he holoi. No laila, loaʻa mau ka nele o ka chromosomal.