A case of intravascular large B-cell lymphoma with renal involvement presenting with elevated serum ANCA titers.

We report the first case of intravascular large B-cell lymphoma (IVLBCL) presenting with vasculitis-like symptoms and elevated serum levels of anti-neutrophil cytoplasmic antibody (ANCA) diagnosed by renal biopsy. The patient exhibited low-grade fever, systemic inflammatory reactions, multiple lung lesions, and persistent proteinuria, which were closely correlated with changes in serum titers of proteinase-3- and myeloperoxidase-ANCA. Preemptive therapy with prednisolone alone partially attenuated these symptoms. Renal biopsy did not reveal histopathological findings suggestive of granulomatous or microscopic polyangiitis. Glomerular and peritubular capillaries were diffusely occluded by CD20-positive large atypical mononuclear cells, with focal foot process effacement of podocytes in the glomeruli. Based on the specific immunophenotype of infiltrated atypical cells, the patient was diagnosed with IVLBCL. Chemotherapy regimens for IVLBCL improved clinical symptoms and led to remission of proteinuria. The ANCA titers decreased in parallel with reductions in the serum levels of the soluble interleukin-2 receptor, suggestive of an association between changes in ANCA levels and IVLBCL-related vascular injuries.