T-Cell Large Granular Lymphocytic Leukemia as a Cause for Severe Neutropenia

Large granular lymphocytic (LGL) leukemia is a rare, indolent disease that can cause destruction of neutrophils. We discuss the case of a previously healthy 63-year-old male who presented with severe, recurrent febrile neutropenia, in whom three bone marrow biopsies over 13 months failed to produce a diagnosis. He presented to our facility with persistent fevers and an absolute neutrophil count of 20 cells/mm³ (reference range 1,700-7,000 cells/mm³). A fourth bone marrow biopsy did not show clonal proliferation, but T-cell LGL leukemia was diagnosed based on the identification of T-cell rearrangements. We propose that LGL leukemia could be an underdiagnosed cause of severe neutropenia in patients with no overt malignancy or immunosuppressive therapy and that population-based database studies of patients with unexplained neutropenia may reveal more cases of this rare disease class.