Long-Term Outcomes and Thrombosis Rates in Patients with Large PNH Clone Managed Without Complement Inhibitors: A 20-Year Follow-Up from a Tertiary Care Centre in North India.

Treatment of paroxysmal nocturnal hemoglobinuria (PNH) patients with a large-size clone is a major challenge in low and middle-income countries. In the absence of complement inhibitors, the response rates with available therapy have not been evaluated in the Indian subcontinent. Retrospective data for patients with a large PNH clone >12 years of age were collected from 2004 to 2024 and were further classified as: Group 1: Classical PNH (c-PNH); Group 2: PNH with aplastic anemia (AA) occurring simultaneously: PNH(L)/AA-s; Group 3: AA preceding the evolution of a Large PNH clone: PNH(L)/AAp. A total of 211 patients were identified with a mean age of 33 years. Of these patients, survivorship status was known for 163 (77.2%), and 111 (52.6%) were under regular follow-up. Out of a total of 211 patients, 49.8% (n-105) cases of c-PNH, 29.4% (n-62) cases of PNH(L)/AA-s, and 20.9% (n-44) cases of PNH(L)/AA-p were identified. Fourteen cases (6.6%) developed thrombosis. Response rates with available drugs in 111 patients were: complete response (CR) in 18% (n-20), partial response (PR) in 65.8% (n-73), and no response (NR) in 16.2% (n-18). Of 57 patients with classical PNH, 20 (35.1%) received low-dose Apixaban (2.5 mg BD) as primary prophylaxis. None developed thrombosis or bleeding. Survivorship status was known for 163 (77.2%) patients. Death occurred in 19% (32/163). The mean survival across all the groups (n-163) was 12.8 years. In the present study, low thrombotic rates were noted in these patients. With available therapy, the overall response rate was 80%, primarily consisting of partial responses.