Another common deficiency is deficiency of factor IX, called hemophilia B (which used to be called Christmas disease, named after the first patient who had it, not the holiday).

另一种常见的缺陷是因子IX缺乏症，称作血友病B（乙型血友病），以前也称作Christmas病，是以第一个被报道的病患命名，而不是指圣诞节。