Relationship between Bone Marrow Megakaryocyte Morphology and the Pathophysiology of ITP

Immune thrombocytopenia (ITP) is a hemorrhagic disease primarily caused by platelet destruction and reduced platelet production from megakaryocytes due to autoantibodies targeting platelet glycoproteins and other antigens, resulting in thrombocytopenia. While the evaluation of bone marrow megakaryocytes is important for distinguishing different causes of thrombocytopenia, recent ITP treatment guidelines state that bone marrow examination itself is not particularly useful for diagnosing ITP. However, there are only a limited number of studies focusing on ITP, particularly on megakaryocyte morphology, indicating that further research is needed. In this study, we compared the morphology of bone marrow megakaryocytes and their platelet production patterns between ITP and control groups. Bone marrow smear specimens were analyzed to measure megakaryocyte major axis length, area, and nuclear area, as well as the number and rate of platelet attachments on megakaryocyte surfaces. The ITP group exhibited greater megakaryocyte major axis length and a larger megakaryocyte area compared to the control group. Furthermore, the number of platelet attachments on megakaryocyte surfaces was significantly lower in ITP patients. Additionally, megakaryocytes in the pregnancy-complicated group had larger major axis length and areas than those in the non-complicated group. In refractory cases requiring thrombopoietin receptor agonists (TPORAs) for treatment, the cell major axis length, cell area, and nuclear area were all larger. The percentage and number of platelet attachments on megakaryocyte surfaces were also lower in patients with Helicobacter pyloripositive (H. pylori-positive) ITP. The morphology of megakaryocytes in ITP exhibits characteristics related to its pathology. Therefore, focusing on the size of megakaryocytes and the appearance of platelet attachments on megakaryocyte surfaces in bone marrow smears may be useful for differentiating ITP.