Synovial fluid involvement in null cell acute lymphoblastic leukemia diagnosed with monoclonal antibodies.

Rheumatic symptoms in patients with leukemia are not uncommon. Often they delay correct diagnosis and therapy. We describe a patient presenting with oligoarticular joint disease in whom immunological analysis of synovial fluid (SF) led to the detection of leukemic cells in the joint. Moreover, analysis with a variety of monoclonal antibodies established the diagnosis of acute lymphoblastic leukemia of null cell type with phenotypically identical malignant cells present in the bone marrow, peripheral blood and SF. Our investigations demonstrate that analysis with monoclonal antibodies is helpful in characterizing joint involvement in patients with leukemia.