Low-grade B cell lymphoma in the perirenal space of the left kidney associated with high titer cold agglutinin disease.

Cold agglutinin disease (CAD) is a subgroup of autoimmune hemolytic anemia caused by monoclonal cold agglutinins produced by clonally expanded B lymphocytes. In primary CAD, lymphoproliferative bone marrow disorder is noted, while as one of the secondary cold agglutinin syndromes (CAS), the initial manifestation of CAD is followed by development of lymphoma. Here, we report a case of low-grade B cell lymphoma developed 3 months after an initial CAD diagnosis. The patient had an extremely high serum cold agglutinin titer (1:16,384) and slightly elevated serum IgM (452 mg/dL; reference, 31-200) with positive monoclonal IgM-kappa chain. After diagnosis of lymphoma-associated CAS, he was managed successfully with six cycles of a BR (bendamustine and rituximab) regimen. Cold agglutinin titers fell rapidly to 1:2048 at 5 months and to 1:512 at 10 months after chemotherapy, and the patient has been in a complete remission for 34 months.