Thromboembolic Events in Indian Patients with Paroxysmal Nocturnal Hemoglobinuria: A Single Centre Experience

Paroxysmal Nocturnal Hemoglobinuria (PNH) is a rare, acquired clonal hematopoietic stem cell disorder. Thrombosis is the most common complication leading to high mortality in PNH patients. The mechanisms of thrombosis in PNH are diverse, and the exact mechanism is still unclear. There is a paucity of data on the incidence of thrombosis in Indian patients with PNH. We retrospectively analyzed the data of 95 patients with a positive PNH clone treated at our center. Ten patients (9.5%), including 07 patients with classical PNH and 03 patients with PNH associated with aplastic anemia or myelodysplastic neoplasm (PNH-AA/MDS), had thromboembolic events. Thrombosis was present in 38% of classical PNH and 10% of PNH AA/MDS. One-third of the patients had 2 or more episodes of thrombosis during the disease. The most common site of thrombosis in our study was the abdominal veins. Fatal thrombosis occurred in 50% of the patients. None of the patients received Eculizumab. The median clone size was higher in cPNH patients compared to PNH AA/MDS. All patients developing thrombosis had a large granulocyte PNH clone and high disease activity. 50% of the patients died as a direct consequence of thrombosis and its complications. Thrombosis despite prophylactic anticoagulation was seen in 25% of patients. The findings, notwithstanding the limited number of patients, confirm that thrombosis continues to remain a significant cause of mortality in patients with PNH.