Waldenström Macroglobulinaemia lymphoma patients have impaired platelet and coagulation function.

Clinical features in patients with the B-cell lymphoma, Waldenström Macroglobulinaemia (WM), include cytopenias, IgM-mediated hyperviscosity, fatigue, bleeding and bruising. Therapeutics such as Bruton's tyrosine kinase inhibitors (BTKis) exacerbate bleeding risk. Abnormal haemostasis arising from platelet dysfunction, altered coagulation or vascular impairment have not been investigated in WM patients. To evaluate haemostatic dysfunction in samples from WM patients. Whole blood (WB) samples were collected from 14 WM patients not receiving therapy, 5 patients receiving BTKis and 15 healthy donors (HDs). Platelet receptor levels and reticulation were measured by flow cytometry, plasma thrombin generation ± platelets by FRET assay, WB clotting potential by rotational thromboelastometry (ROTEM), and plasma soluble glycoprotein VI (sGPVI) and serum thrombopoietin (TPO) by ELISA. Donor platelet spreading, aggregation and ability to accelerate thrombin generation in the presence of WM-derived IgM were assessed. WM platelet receptor levels, responses to physiological agonists and plasma sGPVI were within normal ranges. WM platelets had reduced reticulation (p=0.0012) while serum TPO levels were increased (p=0.0040). WM plasma displayed slower thrombin generation (p=0.0080) and WM platelets contributed less to endogenous thrombin potential (ETP, p=0.0312). HD plasma or platelets incubated with IgM (50-60 mg/mL) displayed reduced spreading (p=0.0002), aggregation (p<0.0001) and ETP (p=0.0081). Alterations to thrombin potential and WB coagulation were detected in WM samples. WM IgM significantly impaired haemostasis in vitro. Platelet and coagulation properties are disturbed in well-managed WM patients.

Bleeding Propensity in Waldenström Macroglobulinemia: Potential Causes and Evaluation.

Waldenström macroglobulinemia (WM) is a rare, incurable, low-grade, B cell lymphoma. Symptomatic disease commonly results from marrow or organ infiltration and hyperviscosity secondary to immunoglobulin M paraprotein, manifesting as anemia, bleeding and neurological symptoms among others. The causes of the bleeding phenotype in WM are complex and involve several intersecting mechanisms. Evidence of defects in platelet function is lacking in the literature, but factors impacting platelet function and coagulation pathways such as acquired von Willebrand factor syndrome, hyperviscosity, abnormal hematopoiesis, cryoglobulinemia and amyloidosis may contribute to bleeding. Understanding the pathophysiological mechanisms behind bleeding is important, as common WM therapies, including chemo-immunotherapy and Bruton's tyrosine kinase inhibitors, carry attendant bleeding risks. Furthermore, due to the relatively indolent nature of this lymphoma, most patients diagnosed with WM are often older and have one or more comorbidities, requiring treatment with anticoagulant or antiplatelet drugs. It is thus important to understand the origin of the WM bleeding phenotype, to better stratify patients according to their bleeding risk, and enhance confidence in clinical decisions regarding treatment management. In this review, we detail the evidence for various contributing factors to the bleeding phenotype in WM and focus on current and emerging diagnostic tools that will aid evaluation and management of bleeding in these patients.