Correlation of clone size with clinical and lab presentation in Paroxysmal nocturnal hemoglobinuria (PNH): A single center experience

Objective: To determine the correlation between clone size in Paroxysmal nocturnal hemoglobinuria and clinical presentation. Methodology: A prospective study was conducted in Armed Forces Bone Marrow Transplant Center (AFBMTC), between 2021-2024. PNH testing was done by multiparametric flow cytometry using fluorescently labeled Alexa-488. PNH clone was labelled as large (>50%) or small (<30%) based on ASH education program 2021. Clone size was correlated with type of presentation of PNH and hemolysis. Statistical analyses were performed using SPSS v 25.0. Results: Out of 324 samples, 96 (29.6 %) were found to have PNH clone by FLAER. Among 75 evaluable cases, 55 (71.2%) were diagnosed as classical hemolytic PNH (CPNH), 16 (21.3%) as PNH in context of marrow failure, 3 (4.2%) as aplastic anemia transformed into PNH, 1 (1.4%) case of MDS with PNH clone. Mean age of patients was 30.97 + 10.56 years. 60 (82.2%) patients were male while 15 (17.3%) were female. On granulocytes, large clone (>50%) was found in 81.3% cases and small clone (<30%) in 18.6% cases. Similarly, 73.3% cases had a large clone on monocytes while 26.6% had a small clone. However, most cases (62.6%) had a smaller RBC clone size. Granulocytic and monocytic clone sizes were significantly associated with Hb and platelet count (p- value <0.05). However, RBC clone size did not show any significant association with the blood counts. Similarly, no significant correlation could be found between markers of hemolysis/ thrombosis. Conclusion: Size of PNH clone impacts the clinical presentation with large PNH clones typically seen in CPNH.