Molecular and Functional Platelet Abnormalities in Myeloproliferative Neoplasms.

Blood platelets are derived from megakaryocytes with functions extending beyond hemostasis to inflammation, immunity, and cancer. Myeloproliferative neoplasms (MPNs) are clonal stem cell disorders driven by somatic mutations affecting JAK-STAT signaling, leading to excessive myeloid proliferation. Thrombosis affects approximately one-fifth of patients at diagnosis and remains elevated throughout the disease course, while the paradoxical coexistence of bleeding further complicates clinical management. In addition, MPNs may progress to advanced disease stages, including bone marrow fibrosis and transformation to acute myeloid leukemia, leading to ineffective hematopoiesis, worsening symptom burden, and poor clinical outcomes. This review outlines how peripherally circulating platelets provide a unique window into MPN pathophysiology, with emphasis on their functional and molecular abnormalities. We summarize current understanding of platelet-mediated hemostatic imbalance across MPN subtypes. We discuss the potential of platelet transcriptomics and proteomics to reveal disease-specific signatures. We further highlight emerging platelet-associated candidates with potential utility as dynamic biomarkers for both the pathological marrow niche and thrombotic and bleeding risk. Together, these insights underscore the potential of platelet-based approaches to complement existing diagnostic and prognostic strategies in MPNs.