Two Cases of Crovalimab-Induced Platelet Recovery in Bone Marrow Failure-Associated Paroxysmal Nocturnal Hemoglobinuria (PNH).

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare, acquired clonal hematopoietic stem cell disorder caused by phosphatidylinositol N-acetylglucosaminyltransferase subunit A (PIG-A) gene mutations, leading to complement-mediated hemolysis, cytopenias, and thrombotic risk. While C5 inhibitors, such as eculizumab and ravulizumab, have transformed PNH management, optimal strategies for bone marrow failure-associated PNH remain unclear. We report two cases of bone marrow failure-associated PNH treated with crovalimab, focusing on its effects on hemolysis and blood cell recovery, particularly platelet counts within four weeks of crovalimab initiation. Case 1: A 79-year-old man presented with mild anemia, thrombocytopenia, elevated LDH, and impaired renal function. Crovalimab initiation resulted in rapid symptom improvement, decreased LDH, and a platelet increase. Case 2: A 22-year-old male athlete exhibited mild anemia, thrombocytopenia, and elevated LDH. Crovalimab resolved the symptoms, there were no hemolytic attacks, and the platelet count increased. Both patients demonstrated prompt improvement in hemolytic parameters and significant platelet recovery following crovalimab initiation, with no serious adverse events. These findings suggest that crovalimab not only attenuates hemolysis but may also improve platelet counts in bone marrow failure-associated PNH, highlighting its broader therapeutic potential and the need for further investigation in larger cohorts.