2025 Volume 74 Issue 3 Pages 605-612
We report a case of diffuse large B-cell lymphoma (DLBCL) presenting with antiphospholipid antibodies. An elderly male patient presented to a local clinic with back pain and was found to have multiple bone lesions. PET-CT revealed lymph node enlargement with high FDG uptake, leading to referral to our hospital for further evaluation and treatment. Initial laboratory findings showed prolonged APTT (61.0 sec), elevated IgM (1,239.3 mg/dL), and increased sIL-2R (2,608 U/mL). Immunofixation identified both IgM κ and IgM λ M-proteins. Lymph node biopsy revealed CD5, CD19, and CD20 positive cell populations, confirming the diagnosis of DLBCL. Further investigation of prolonged APTT showed inhibitor patterns in both immediate and delayed mixing tests. Russell’s viper venom time was 1.27, and ELISA detected only IgM anticardiolipin antibodies (aCL). Despite these findings, antiphospholipid syndrome was not diagnosed due to the absence of thrombotic events. Treatment with dexamethasone and local radiation therapy was initiated, followed by rituximab-based chemotherapy. APTT normalized concurrent with declining IgM levels, suggesting that prolonged APTT was caused by β2GPI-independent IgM aCL, based on ELISA methodology. This case highlights the importance of careful interpretation of laboratory results in patients with M-proteins. Moreover, as DLBCL with IgM M-protein reportedly carries a poor prognosis, careful monitoring of disease progression is warranted.
