Unmasking the Hidden Culprit: Aplastic Crisis Revealing Underlying Large Granular Lymphocytic Leukemia

Introduction/Background/Significance: Large granular lymphocytic (LGL) leukemia is a rare, indolent lymphoproliferative disorder often associated with cytopenias and autoimmune features. Its subtle and chronic course can delay diagnosis for years. This case highlights an unusual presentation of LGL leukemia, unmasked by parvovirus B19 infection, presenting as an acute aplastic crisis.

Materials and Methods/Case Presentation/Objective: Case presentation

Results/Description/Main Outcome Measure(s)

A 58-year-old woman with a history of chronic neutropenia and intermittent anemia presented with increasing fatigue, easy bruising, and dyspnea on exertion. She had recently recovered from a self-limited viral illness. Initial labs revealed pancytopenia: hemoglobin 6.9 g/dL, WBC 1.1 K/μL, ANC 150/μL, and platelets 34 K/μL. Reticulocyte count was low, and LDH was mildly elevated. Peripheral smear showed occasional large granular lymphocytes.

Bone marrow biopsy demonstrated marked hypocellularity (20%) with interstitial infiltrates of CD3+, CD8+, and CD57+ cytotoxic T cells. T-cell receptor gene rearrangement studies confirmed clonality, establishing the diagnosis of T-cell LGL leukemia. Concurrently, serum PCR was positive for parvovirus B19, suggesting a viral trigger precipitating the aplastic crisis. The patient received IVIG and supportive transfusions, followed by low-dose methotrexate for the underlying LGL leukemia. Over subsequent weeks, blood counts gradually improved. This case illustrates how viral infections can unmask underlying marrow disorders, particularly in patients with preexisting cytopenias. LGL leukemia often presents insidiously and may be overlooked without appropriate flow cytometry and molecular testing. The diagnostic challenge lies in distinguishing transient marrow suppression from clonal marrow pathology, especially when both coexist.

Conclusions: Clinicians should maintain a high index of suspicion for LGL leukemia in patients with chronic neutropenia or unexplained pancytopenia, particularly when triggered by viral illness. Early identification and treatment can reverse marrow failure and improve outcomes.

References

LGL leukemia, aplastic crisis, pancytopenia, parvovirus B19, cytotoxic T cells, marrow failure, autoimmune cytopenia

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