Haemorrhagic thrombocythaemia due to defect platelet adhesiveness

The myeloproliferative disorders. An historical appraisal and personal experiences

According to strict morphological, biochemical and cytogenetic criteria Philadelphia chromosome positive essential thrombocythemia and chronic granulocytic leukemia constitute a separate malignant and individual disease entity, whereas Philadelphia chromosome negative essential thrombocythemia, polycythemia vera and agnogenic or megakaryocytic myeloid metaplasia form a chronic proliferation of three hematopoietic cell lines. Histopathology from bone marrow biopsies permits the characterization and diagnostic differention of the various myeloproliferative disorders and appears to be a main and specific diagostic criterion for polycythemia vera and essential thrombocythemia. Hemorrhagic thrombocythemia is a clinical syndrome of recurrent spontaneous mucocutaneous and secondary hemorrhages often preceded by thromboses, extremely high platelet counts, pseudohyperkalemia, increased bone marrow cellularity and frequently splenomegaly. The diagnostic criteria of essential thrombocythemia with paradoxical occurrence of thrombotic events and hemorrhagic manifestations are a platelet count in excess of 1000 x 10(9)/L and increased bone marrow cellularity in the majority of the cases. Erythromelalgia and other microcirculatory ischemic or thrombotic events or accidents in essential thrombocythemia and polycythemia vera already occur at platelet counts in excess of the upper limit of normal. First line treatment options in essential thrombocythemia and polycythemia vera are control of platelet function with low-dose aspirin and reductive control of platelet count and erythrocytes by bloodletting, interferon and busulfan or hydroxyurea monochemotherapy.

Granulocyte and platelet adhesiveness in malignant paraproteinaemia, leukaemia and myeloproliferative diseases

Granulocyte and platelet adhesiveness were measured in 36 patients with haematologic diseases, using a glass bead column assay. Platelet adhesiveness (PA) was reduced in malignant paraproteinaemia (l3/20), leukaemia (10/11) and myeloproliferative diseases (3/5). Granulocyte adhesiveness (GA) was reduced in most patients with paraproteinaemia and leukaemia, but results of measurements in whole blood and in suspensions of leucocytes in autologous plasma were poorly correlated due to the influence of abnormal platelet function and/or concentration on the measurement of GA in whole blood. The results of experiments combining leucocytes and plasma from patients and controls indicate that impaired GA in paraproteinaemia is due to a plasma factor, whereas a cellular defect is responsible for the reduced GA in leukaemia.

Thrombocytopathy in preleukaemia: association with a defect of thromboxane A2 activity

Platelet aggregation and the platelet prostaglandin pathway have been investigated in two patients with preleukaemic states who had a haemorrhagic tendency but a normal platelet count. In both patients platelet aggregation induced by collagen adenosine diphosphate (ADP) and arachidonic acid (AA) were abnormal. Malonyldiadehyde (MDA) production from exogenous AA was normal in both patients thus excluding cyclo-oxygenase deficiency. The platelet aggregating and rabbit aorta contracting activities of thromboxane A2 (TxA2) were very low in both patients. Production of thromboxane B2 (TxB2) assessed by thin layer chromatographic separation of the metabolites of [1(-14)C]AA and by radioimmunoassay, was normal. These abnormalities of platelet function appear to be due to the production of TxA2 with a low biological activity.

Chronic myeloproliferative disorders: improved platelet aggregation following venesection

Venesection of 10% of whole blood volume or plateletpheresis was performed in nine patients with chronic myeloproliferative disorders and in five normal control subjects. Before venesection, the patients showed impaired platelet aggregation in 33% of tests, most often in response to stimulation with 9 mumol adrenaline. After venesection, the platelet and megathrombocyte counts increased rapidly and excessively in most patients and platelet aggregation improved markedly. In some cases, spontaneous in vitro aggregation was seen at high platelet concentrations. In two patients impaired platelet aggregation with adrenaline was not corrected. The splenic platelet pool is thought to be the probable source of the new platelets.

[Morphological and functional studies in a case of primary (idiopathic) thrombocythaemia in childhood (author's transl)]

Primary (idiopathic) thrombocythaemia is a rare disease in childhood. Haemorrhagic diathesis and splenomegaly are principal findings besides thrombocytosis. The cases of a nine year old girl with thrombocyte levels between 2.8 and 4.5 X 10(6) microliter is described. The examination in light and electron microscopy revealed various morphological abnormalities in thrombocytes and megakaryocytes. Platelet function was disturbed in various degrees. The impact of functional abnormalities on the haemorrhagic diathesis is discussed. The findings in this child were compared to those of the better characterized picture of primary and secondary thrombozytosis in adulthood. Possible pathogenic relations to myeloproliferative diseases are also discussed.

Defective platelet lipid peroxidation in myeloproliferative disorders: a possible defect of prostaglandin synthesis

Platelet lipid peroxidation induced by the sulphydryl blocking reagent n-ethylmaleimide [NEM] was measured by production of malonyldialdehyde [MDA]. Lipid peroxidation was decreased in five of 10 patients with proven myeloproliferative disease. The low levels of lipid peroxidation correlated well with in vitro and in vivo tests of platelet function and the bleeding and bruising problems. The reduction in lipid peroxidation with NEM may be due to one or more of the following: [i] an aged platelet population; [ii] an abnormal cell line; [iii] a reduction of the cyclo-oxygenase enzyme activity in the platelet prostaglandin synthetic pathway; [iv] a reduction of the substrate for platelet prostaglandin synthesis, Arachidonic acid; and [v] an abnormality of phospholipase A activation.