Waldenström macroglobulinemia (WM) is a rare, slow-growing cancer. It is a form of non-Hodgkin lymphoma. WM is also known as lymphoplasmacytic lymphoma.
WM begins in the immune system. It starts in white blood cells called B lymphocytes (B cells). B cells play a key role in the body's immune system. Some B cells develop into plasma cells. Plasma cells make antibodies (also called immunoglobulins). Antibodies help the body attack bacteria, viruses, and other foreign substances.
Sometimes B cells become cancerous before turning into mature plasma cells. These abnormal B cells multiply out of control. They produce large amounts of IgM antibody (immunoglobulin M). High levels of IgM can cause a person's blood to thicken. This makes it harder for blood to flow through the body. (Multiple myeloma, another form of cancer of plasma cells, causes similar abnormalities. The type of immunoglobulin the cells produce helps distinguish one from the other.)
As they grow out of control, lymphoma cells can crowd out the cells that normally develop into healthy blood cells. This can lead to low numbers of red blood cells, white blood cells, and platelets. Low levels of these blood cells trigger many of the symptoms associated with WM.
The cells involved in WM grow mostly in the bone marrow. The bone marrow is the soft, spongy tissue inside most bones.
WM mainly affects older adults. It is not curable, but it is usually treatable.