Diffuse Large B-cell Lymphoma Initially Managed As Secondary Immune Thrombocytopenia: A Case Report.

Immune thrombocytopenia (IT) is an autoimmune disorder characterized by isolated thrombocytopenia resulting from increased platelet destruction and impaired production. Although most cases are idiopathic, secondary causes, including malignancies, should be considered, particularly in atypical or treatment-resistant presentations. Non-Hodgkin lymphomas (NHL) may rarely present with autoimmune cytopenias, leading to diagnostic challenges. We report the case of a 77-year-old male patient presenting with fatigue, weight loss, severe thrombocytopenia, anemia, and leukopenia who was initially managed as having IT. Lack of response to corticosteroids and intravenous immunoglobulin (IVIG) prompted further evaluation. Peripheral smear findings, PET/CT imaging, splenomegaly, and myelophthisic features raised suspicion for lymphoma. The initial bone marrow biopsy was inconclusive; however, platelet counts transiently improved following rituximab therapy. Repeat bone marrow biopsy confirmed diffuse large B-cell lymphoma (DLBCL), and the patient was subsequently treated with R-mini-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone administered at reduced doses) chemotherapy, resulting in normalization of platelet counts and significant clinical improvement. This case highlights the importance of reconsidering secondary causes in refractory IT and emphasizes the diagnostic value of repeated bone marrow evaluation in suspected lymphoproliferative disorders.