Summary
The blood coagulation system has been studied in 7 patients with thrombocythaemia.
4 of these patients had thrombocythaemia after splenectomy, 2 of them had thrombocythaemia
associated with myeloid leukemia, and 1 thrombocythaemia associated with polycythaemia.
Severe bleeding episodes were noted in 5 cases, 2 patients had only mild bleeding
symptoms.
Each patient was examined several times. The period of observations varied from 2
months to 3 years. Platelet count varied from 350 000 to 3 800 000 per mm3.
Bleeding time and tourniquet test were normal in all cases. Routine coagulation and
fibrinolysis studies did not reveale characteristic abnormalities in plasma clotting
factors. A decrease of prothrombin complex components was observed in 4 cases. This
disturbance was due to the coexisting injury of liver parenchyma or myeloid changes
but not to an increase of platelets or to the abnormalities in the platelet system.
An increase of antiheparin activity was found in the plasma of 4 patients. This activity
is probably due to the escape of platelet factor 4 from destroyed or qualitatively
changed platelets into plasma.
Platelet clotting factors were investigated in isolated platelet suspensions, A significant
decrease of platelet factor 1 was observed in all patients and a decrease of platelet
factor 4 in 5 patients. In 2 cases platelet factor 4 increased. Platelet thromboplastic
activity showed a great variety of disturbances in conformity with other workers observations.
Recent views on the pathogenesis of bleedings in thrombocythaemia are discussed. On
the basis of their own investigations the authors suggest that the significant disturbances
of platelet function may contribute to the development of bleeding, and that the increase
of antiheparin activity in plasma may produce hypercoagulability and favorize the
formation of thrombi.
