Objective To understand the clinical characteristics, diagnostic and differential diagnostic methods of brucellosis and diffuse large B-cell lymphoma（DLBCL）, the possible relationship between the two diseases and improve the understanding of clinical physicians about the two diseases.

Methods Clinical and epidemiological information of a brucellosis case complicated with DLBCL in Weifang were collected from the medical records, and blood samples were collected from the case for laboratory examinations, such as serum agglutination test and blood culture. Imaging examinations, such as spinal magnetic resonance imaging and orbital computed tomography, were performed, and the pathological analysis on the bone marrow aspirate was performed.

Results The case was a young man who had frequent contacts with raw lambs. The main clinical manifestations of the case were lower back pain and joint pain. The serum agglutination test for Brucella was positive, and Brucella was isolated from blood culture. Bone marrow pathology and immunohistochemistry suggested DLBCL. The case received standardized anti-brucellosis treatment, immunochemotherapy, and bone marrow transplantation, but he died of severe infection after bone marrow transplantation eventually.

Conclusion Brucellosis complicated with DLBCL is rare, but it still needs attention by clinical physicians. During the diagnostic process, it is necessary to conduct comprehensive examination and evaluation to exclude other possible diseases.