Acquired Factor X Deficiency

Isolated factor X deficiency in association with abnormal plasma antithrombin activity was recognized in a 59-year-old man with amyloidosis and signs and symptoms of calf pain suggestive of thrombophlebitis. Venographic studies excluded venous thrombosis, and, despite major coagulation abnormalities, there was no hemorrhagic tendency. Infusion of plasma at maximum tolerable volume did not result in a rise in factor X activity, nor in alteration in antithrombin activity. The latter abnormality appears to be unique and, to our knowledge, has not been reported previously in association with amyloidosis. ( JAMA 230:1658-1660, 1974)