“…To date only about 25 proven or probable cases have been reported in the literature [2-4, 6-8, 14, 19,21,23,[25][26][27][28][29][30][31]. The reasons for such rarity are unknown and seem really striking if one takes into ac count the fact that congenital factor VII deficiency, a condition which re sembles factor X deficiency, is at least 4 times more frequent [16], Recently several patients with a coagulation disorder due to the pres ence of an abnormal factor X have been described [13,14,15,17].…”