1. Thirteen cases of plasma thromboplastin component (PTC) deficiency or Christmas disease are reviewed and summarized. Of these cases, only in one were the whole blood coagulation time and prothrombin consumption normal.
2. Two cases of a mild bleeding disorder, occurring in brothers with slightly prolonged whole blood coagulation times and normal prothrombin consumption are described.
3. In these two cases, the thromboplastin generation test revealed the deficiency of a serum factor essential for normal thromboplastin generation. A mild deficiency of PTC was demonstrated by the correction of the serum deficiency by the addition to the patients’ serum of a partially purified preparation of PTC.
4. The differentiation of PTC deficiency from hemophilia is discussed.
5. Mild bleeding disorders due to a moderate reduction of antihemophilic globulin (AHG) or PTC can be differentiated by the use of the thromboplastin generation test.