Large Granular Lymphocytosis With Cytopenias After Allogeneic Blood or Marrow Transplantation: Clinical Characteristics and Response to Immunosuppressive Therapy

Large granular lymphocytosis (LGL)—or LGL leukemia—is a T- or NK-cell lymphoproliferative disorder that often results in cytopenias and autoimmune phenomena. Several studies have described LGL in a subset of patients after allogeneic blood or marrow transplantation (alloBMT), almost exclusively in the setting of asymptomatic lymphocytosis. Some have suggested an association with improved transplant-related outcomes. In contrast, clinically significant LGL after alloBMT is only described in small case reports. This study sought to assess the characteristics, significance, and response to treatment of LGL associated with unexplained anemia, thrombocytopenia, or neutropenia after alloBMT. We performed a retrospective analysis of 150 patients who were evaluated for LGL by peripheral blood flow cytometry (LGL flow) for unexplained cytopenias following initial engraftment after alloBMT from January 1 2012 to July 1, 2019. We identified patients with abnormally increased populations of LGL cells (LGL+) as assessed by Johns Hopkins Hematopathology. We collected demographic, transplantation, and LGL treatment information from electronic medical records. We compared LGL+ patients to patients with unexplained cytopenias with negative flow cytometry for LGL (LGL−) in this cohort. We also assessed change in blood counts after 4 weeks of immunosuppressive therapy in LGL+ patients. Cytopenias occurred at a median of 5.7 months (range 1-81) after alloBMT. The majority of the transplants were nonmyeloablative from haploidentical donors, and all patients received post-transplantation cyclophosphamide for graft-versus-host disease prophylaxis, consistent with the overall alloBMT characteristics at our center. We identified 70 patients with LGL and cytopenias, representing 47% of those evaluated by flow cytometry. There were no significant demographic or transplant-related differences between LGL+ patients and LGL− patients. The median age was 59, and 63% were male. LGL+ patients were more likely to have had cytomegalovirus (CMV) viremia (73% versus 28%, P <.0001), but not acute or chronic graft-versus-host disease. LGL+ patients had higher absolute lymphocyte counts (1500 versus 485/ mm³, P <.0001), a trend toward lower absolute neutrophil count (660 versus 965/mm³, P =.17), and lower neutrophil to lymphocyte ratio (0.39 versus 1.71, P <.001). There were no differences in overall survival or relapse-free survival. Of those with T-cell LGL, 45 were assessed for T-cell receptor clonality. In all, 22% were clonal, 53% oligoclonal, 4% polyclonal, and 20% indeterminate. Thirty (43%) LGL+ patients received immunosuppressive therapy (IST) for cytopenias. First-line treatment was corticosteroids for 25 (83%). Among those treated, there was an increase in median absolute neutrophil count from 720 before treatment to 1990/mm³ after 4 weeks (P =.0017). Thrombocytopenia and anemia showed at most a mild improvement with IST. LGL was a common association with otherwise unexplained cytopenias after alloBMT, almost always after prior CMV infection. LGL in the setting of cytopenias did not predict improved transplantation outcomes compared to those with cytopenias without presence of LGL. IST was effective at improving neutropenia associated with LGL after alloBMT.