Thrombocytosis

THROMBOCYTOSIS, i. e., an increase in the number of blood platelets (Bizzozero's plaques) in the peripheral blood, occurs either as a result of their redistribution through the bloodstream (during the dilation of peripheral vessels and constriction of mesenteric vessels due to irritation of the splanchnic nerves) or through their enhanced formation. Most authors attribute the function of blood platelet formation to megakaryocytes located in the bone marrow. Thrombocytosis associated with an increase in the total number of blood platelets usually also reveals an increase in the number of megakaryocytes in the bone marrow. This is especially pronounced in polycythemia, in which fragments of megakaryocytes are also found in the blood, often with disintegration of the protoplasm into platelets; less frequently, megakaryocytes are observed in the blood in myelogenic leukemia. Large and prolonged thrombocytosis is noted after surgical removal of the spleen. Hypochromic anemias, especially after hemorrhages, also proceed with thrombocytosis. The recovery period after infectious diseases frequently proceeds with thrombocytosis as well. Postoperative thrombocytosis reaches its peak on the 10th to 14th day; in cases where postoperative blood vessel thromboses take place, the platelet count decreases significantly. In thrombocytosis, giant platelets and large accumulations of platelets in the form of tails are frequently encountered. Characteristic thrombocytosis in athletes—the so-called Trainings-thrombocytose—is explained by the adrenalineemia occurring in athletes at the beginning of exercises, which leads to contraction of the spleen, from which a large number of platelets enter the blood. Acute poisoning with pyridine, phenylhydrazine, and hydroxylamine is accompanied by thrombocytosis. Upon taking a hypotonic solution of sodium chloride per os, the number of blood platelets also increases. Thrombocytosis in asphyxia is characterized by a reduced ability of platelets to clump together; the same inferiority of platelets is revealed in the so-called Glanzmann's thrombasthenia, which, despite frequently existing thrombocytosis, proceeds with phenomena of hemorrhagic diathesis. Italian authors describe an isolated, leukemia-like disease of the megakaryocytes of the "third myelogenic system," which they propose to call thrombocythemia. This view has not yet found general recognition. Lit.—see literature to the article Thrombocytopenia. E. Freifeld.