Abstract
T-cell large granular lymphocytic leukemia (T-LGLL) is an indolent clonal lymphoproliferative disorder that primarily affects individuals over the age of 60. Its occurrence in young adults is exceedingly rare, with fewer than five well-documented cases reported in the literature.
We present a case of a 24-year-old previously healthy woman who developed progressive fatigue and pancytopenia. Laboratory testing revealed hemoglobin 9.9 g/dL, absolute neutrophil count 1.1 ×10⁹/L, and platelet count 15 ×10⁹/L. Bone marrow biopsy showed mild hypercellularity, megakaryocytic hyperplasia, and infiltration by atypical large granular lymphocytes. Flow cytometry identified a clonal population of CD3+, CD8+, CD57+, TCR-αβ+ lymphocytes comprising 46% of lymphoid cells. T-cell receptor (TCR) beta gene rearrangement studies confirmed clonality. Cytogenetic analysis demonstrated a normal female karyotype, and molecular testing was negative for myeloid-associated mutations including JAK2, CALR, and MPL. There was no evidence of underlying autoimmune or rheumatologic disease.
This case is notable for its early age of onset, profound pancytopenia, and extensive marrow infiltration without autoimmune manifestations. Prior reports by Lamy et al. and Sokol et al. have described similar presentations in young adults, occasionally associated with STAT3 mutations or immune-mediated cytopenias.
The patient was treated with oral methotrexate 10 mg once weekly, folic acid 1 mg daily, and prednisone 20 mg daily. She was discharged with close outpatient follow-up and has demonstrated a significant hematologic response.
This case highlights the importance of considering clonal T-cell proliferative disorders in the differential diagnosis of unexplained cytopenias—even in young adults. It expands the clinical spectrum of early-onset T-LGLL and underscores the need for increased recognition, timely diagnosis, and further research into its pathogenesis and optimal therapeutic strategies.
