Anti-factor IX circulating anticoagulant and immune thrombocytopenia in a case of Takayasu's arteritis.

A 38-year-old male with proven Takayasu's arteritis presented, in a routine investigation, with thrombocytopenia, prolonged whole blood clotting time and activated partial thromboplastin time. Further studies demonstrated low levels of factor IX caused by a circulating anticoagulant. Immunological studies revealed an IgG (with kappa chains predominance) nature of this. Corticoid therapy decreased but did not suppress the anticoagulant activity. Since similar coagulation abnormalities have been described in collagen diseases, this observation is in support of this etiology to be considered in Takayasu's arteritis.