Summary
A 62 year old man acquired a temporary, virtually complete, deficiency of prothrombin as measured by both the Iowa and Oxford 2-stage methods. The etiology agent (or agents) is not known, but one of the drugs listed in Table 1 or an interaction between several was probably responsible. There was no evidence of an inhibitor, and factors I (fibrinogen), V (AcG), VII (SPCA), VIII (AHF), IX (PTC), X (Stuart), and XII (Hageman) were demonstrated to be normal. There were other evidences of mild liver damage and the prothrombin deficiency did not respond immediately to injections of natural vitamin K. Greatly prolonged clotting times but only moderately prolonged prothrombin times and partial thromboplastin times were observed. Bleeding was very severe into many tissues. Thromboplastin generation proceeded normally in the patient’s pro-thrombin-deficient plasma, despite the appearance of only a trace of thrombin. This patient’s history and clotting profile argue against the concept that factor VII (SPCA) and IX (PTC) are derivatives of prothrombin.
