Myelofibrosis-associated extramedullary hematopoiesis: Insights into hepatic, pulmonary, and thrombotic complications.

BACKGROUND

Primary myelofibrosis (PMF), the most aggressive of the Philadelphia chromosome-negative myeloproliferative neoplasms (MPNs), is characterized by progressive marrow fibrosis, ineffective hematopoiesis, and a pro-inflammatory milieu. These pathobiologic features drive extramedullary hematopoiesis (EMH) and confer heightened risks for hepatic, pulmonary, and thrombotic complications, particularly in patients undergoing allogeneic hematopoietic stem cell transplantation (allo-HCT).

OBJECTIVE

Drawing on our institutional transplant experience in PMF, we review the pathophysiology, clinical manifestations, and management of EMH-related complications to optimize outcomes in this complex patient population.

METHODS

We synthesized current literature on EMH in MPNs and integrated contemporary data on hepatic portal hypertension, pulmonary hypertension, splanchnic vein thrombosis, and transplant-related complications. Key insights from recent European Society for Blood and Marrow Transplantation (EBMT) registry data are highlighted.

RESULTS

Portal hypertension affects 3-18 % of patients with myeloproliferative neoplasms (MPNs), driven by intrahepatic sinusoidal infiltration, splenic hyperdynamic circulation, and splanchnic thrombosis. Splanchnic vein thrombosis often precedes overt MPN diagnosis, with JAK2V617F detected in a substantial proportion of affected patients. Pulmonary complications-including extramedullary hematopoiesis (EMH), pulmonary hypertension, and peri-engraftment respiratory failure-contribute meaningfully to non-relapse mortality in the transplant setting. Ruxolitinib, reduced-intensity conditioning, and spleen-directed strategies have improved engraftment kinetics and mitigated graft-related complications in myelofibrosis patients undergoing allogeneic hematopoietic stem cell transplantation (allo-HCT). Institutional observations are incorporated throughout to contextualize hepatic, pulmonary, and vascular manifestations of EMH in contemporary practice.

CONCLUSION

These institutional observations complement published data and emphasize that EMH-related hepatic, pulmonary, and vascular complications are biologically active yet potentially reversible when clonal disease control is achieved. EMH-associated complications in PMF require a multidisciplinary management approach tailored to disease biology and transplant considerations. Advances in cytokine modulation, conditioning strategies, and emerging antifibrotic agents hold promise for improving patient outcomes.