Aspirin responsive platelet thrombophilia in essential thrombocythemia and polycythemia vera

Figure 5 The effect of anagrelide treatment on CD61⁺ stained megakaryocyte size, proliferation and differentiation in bone marrow biopsies. A: Change of megakaryocyte size from large before treatment (a and b) to small after treatment (c and d) with anagrelide, a selective inhibitor of megakaryocyte differentiation; B: The peculiar phenomenon of megakaryocyte change by anagrelide is generated by an arrest of endomitotic activity of the thrombocythemia-specific reversion of large to small megakaryocytes before and after anagrelide treatment in essential thrombocythemia (ET, left) and in hypercellularfalse ET (early prefibrotic stage chronic idiopathic myelofibrosis, right). Before anagrelide therapy (platelets 9.7 × 10¹¹/L), the megakaryocytes in ET are loosely clustered with predominance of large and giant forms (a, b). After 1 year anagrelide monotherapy (platelets 4.5 × 10¹¹/L), the megakaryocytes are small (c, d), but the number of small megakaryocytes remained increased (d). Originated from Michiels et al[58].