Abstract
T-cell large granular lymphocytic leukemia (T-LGLL) is an uncommon lymphoproliferative disorder that typically follows a slow clinical course. Symptoms often remain subtle until cytopenia or infection develops. Severe infection secondary to neutropenia represents the major cause of mortality. We describe an uncommon case involving an 81-year-old woman diagnosed with T-LGLL whose agranulocytosis was followed by recurrent infections. Immunosuppressive agents such as methotrexate, cyclophosphamide, and tacrolimus-commonly recommended by current guidelines-were administered but failed to improve neutropenia. Administration of fludarabine, a purine analog listed as a second-line option in the NCCN guidelines, led to a prompt rise in neutrophil counts and a concomitant decline in LGL levels. To our knowledge, no prior Japanese report has documented successful use of fludarabine monotherapy for T-LGLL-related neutropenia, prompting us to describe this case.