T-cell large granular lymphocytic (LGL) leukemia consists of CD4 + /CD8 dim and CD4 - /CD8 + LGL populations in association with immune thrombocytopenia, autoimmune neutropenia, and monoclonal B-cell lymphocytosis.

CD3 ⁺ /CD57 ⁺ T-cell large granular lymphocyte leukemia (T-LGLL) is an indolent neoplasm, exhibiting mostly CD8 ⁺ , less frequently CD4 ⁺ phenotypes, and T-LGLL consisting of 2 populations with CD8 ⁺ and CD4 ⁺ phenotypes is markedly rare. An 87-year-old female was admitted under a diagnosis of immune thrombocytopenia (ITP) with a platelet count of 5.0×10 ⁹ /L and increased number of LGL with unknown etiology. Her neutrophil count also decreased to 0.27×10 ⁹ /L and she was positive for antineutrophil antibody. The WBC count was 2.7×10 ⁹ /L with 34.7% LGL and flow cytometry (FCM) analysis revealed 16% CD3 ⁺ /CD4 ⁺ /CD8 ^dim /CD57 ⁺ and 20.9% CD3 ⁺ /CD8 ⁺ /CD57 ⁺ populations. These populations also expressed granzyme B and perforin. Circulating mononuclear cells were found to be clonal by PCR analysis of T-cell receptor β-chain gene. Serum immunofixation and bone marrow FCM analyses demonstrated 2 clonal B-cells producing IgG-λ and IgA-λ. Deep amplicon sequencing of STAT3 and STAT5B genes revealed a STAT3 R302G mutation with an allele burden of 2.6%. The thrombocytopenia and neutropenia were successfully treated by prednisolone and romiplostim with negative conversion of antineutrophil antibody. This is the first reported case of T-LGLL with dual components of CD4 ⁺ /CD8 ^dim and CD4 ^- /CD8 ⁺ populations in terms of multiple comorbidities related to the respective CD8 ⁺ and CD4 ⁺ T-LGLLs.