Decrease in PNH-type Blood Cells after the Cessation of Thrombopoietin Receptor Agonist in a Case of AA-PNH Syndrome.

A 64-year-old male with severe aplastic anemia was initially treated by immunosuppressive therapy, with a partial response. Subsequent thrombopoietin receptor agonist (TPO-RA) therapy resulted in a sustained recovery of cytopenia. After a few years, a gradual increase in the serum lactate dehydrogenase levels was observed, and a massive expansion of paroxysmal nocturnal hemoglobinuria (PNH) clones was established. TPO-RA was discontinued after a transient hemolytic episode of SARS-CoV-2 infection. A follow-up analysis revealed a decrease in the number of PNH clones. Although his blood counts declined moderately, they remained stable without transfusion support, suggesting that although PNH clones may expand under TPO-RA treatment, their withdrawal may facilitate regression.