Unprovoked Venous Thromboembolism in a Patient with a Small PNH Clone: A Therapeutic Dilemma

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare clonal hematopoietic stem cell disorder commonly presenting with hemolytic anemia and thrombosis. Treatment of acute thrombotic events usually involves a combination of complement inhibitor therapy and anticoagulation. We report the case of a 69-year-old female with history of PNH in spontaneous remission who presented nearly two decades later with unprovoked venous thromboembolism (VTE). Flow cytometry detected a small PNH without evidence of hemolysis, creating a dilemma regarding the need for complement inhibitor therapy. She was ultimately treated with anticoagulation alone. This case highlights the unknown aspects of the natural history of PNH and the challenges in managing venous thromboembolism in patients with persistent small PNH clones.