Waldenström's macroglobulinemia (WM, also known as lymphoplasmacytic lymphoma) is cancer involving a subtype of white blood cells called lymphocytes. The main attributing antibody is IgM. It is a type of lymphoproliferative disease, and shares clinical characteristics with the indolent non-Hodgkin lymphomas.
It is named after the Swedish physician Jan G. Waldenström, who first identified the condition.
For a period of time, WM was considered to be related to multiple myeloma due to the presence of monoclonal gammopathy and infiltration of the bone marrow and other organs by plasmacytoid lymphocytes. The new World Health Organization (WHO) classification, however, places WM under the category of lymphoplasmacytic lymphomas, itself a subcategory of the indolent (low-grade) non-Hodgkin lymphomas.
Of all cancers involving the same class of blood cell, 1% of cases are WM.
WM is a rare disorder, with fewer than 1,500 cases occurring in the United States annually. The median age of onset of WM is between 60 and 65 years, with some cases occurring in late teens.
The laboratory diagnosis of Waldenström macroglobulinemia is contingent on demonstrating a significant monoclonal IgM spike and identifying malignant cells consistent with Waldenström macroglobulinemia (usually found in bone marrow biopsy samples and aspirates). General studies include a CBC count, red cell indices, platelet count, and a peripheral smear. Normocytic normochromic anemia, leukopenia, and thrombocytopenia may be observed. Anemia is the most common finding, present in 80% of patients with symptomatic Waldenström macroglobulinemia.
The peripheral smear may reveal plasmacytoid lymphocytes, normocytic normochromic red cells, and rouleaux formation.
Neutropenia can be found in some patients.
Thrombocytopenia is found in approximately 50% of patients with bleeding diathesis. Chemistry tests include lactate dehydrogenase (LDH) levels, uric acid levels, erythrocyte sedimentation rate (ESR), renal and hepatic function, total protein levels, and an albumin-to-globulin ratio. The ESR and uric acid level may be elevated. Creatinine is occasionally elevated and electrolytes are occasionally abnormal. Hypercalcemia is noted in approximately 4% of patients. The LDH level is frequently elevated, indicating the extent of Waldenström macroglobulinemia–related tissue involvement. Rheumatoid factor, cryoglobulins, direct antiglobulin test and cold agglutinin titre results can be positive. Beta-2-microglobulin and C-reactive protein test results are not specific for Waldenström macroglobulinemia. Beta-2-microglobulin is elevated in proportion to tumor mass. Coagulation abnormalities may be present. Prothrombin time, activated partial thromboplastin time, thrombin time, and fibrinogen tests should be performed. Platelet aggregation studies are optional. Serum protein electrophoresis results indicate evidence of a monoclonal spike but cannot establish the spike as IgM. An M component with beta-to-gamma mobility is highly suggestive of Waldenström macroglobulinemia. Immunoelectrophoresis and immunofixation studies help identify the type of immunoglobulin, the clonality of the light chain, and the monoclonality and quantitation of the paraprotein. High-resolution electrophoresis and serum and urine immunofixation are recommended to help identify and characterize the monoclonal IgM paraprotein.
The light chain of the monoclonal protein is usually the kappa light chain. At times, patients with Waldenström macroglobulinemia may exhibit more than one M protein. Plasma viscosity must be measured. Results from characterization studies of urinary immunoglobulins indicate that light chains (Bence Jones protein), usually of the kappa type, are found in the urine. Urine collections should be concentrated.
Bence Jones proteinuria is observed in approximately 40% of patients and exceeds 1 g/d in approximately 3% of patients. Patients with findings of peripheral neuropathy should have nerve conduction studies and antimyelin associated glycoprotein serology
In 2002, a panel at the International Workshop on Waldenstrom Macroglobulinemia agreed on criteria for the initiation of therapy. They recommended starting therapy in patients with constitutional symptoms such as recurrent fever, night sweats, fatigue due to anemia, weight loss, progressive symptomatic lymphadenopathy or splenomegaly, and anemia due to marrow infiltration. Complications such as hyperviscosity syndrome, symptomatic sensorimotor peripheral neuropathy, systemic amyloidosis, renal insufficiency, or symptomatic cryoglobulinemia were also suggested as indications for therapy.
Treatment includes the monoclonal antibody rituximab, sometimes in combination with chemotherapeutic drugs such as chlorambucil, cyclophosphamide, or vincristine. Corticosteroids may also be used in combination. Plasmapheresis can be used to treat the hyperviscosity syndrome by removing the paraprotein from the blood, although it does not address the underlying disease.
Recently, autologous bone marrow transplantation has been added to the available treatment options.
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