What Is Waldenstrom Macroglobulinemia?

Waldenstrom macroglobulinemia (WM) is a type of non-Hodgkin lymphoma (NHL). The cancer cells make large amounts of an abnormal protein (called a macroglobulin). Another name for WM is lymphoplasmacytic lymphoma. This condition used to be called Waldenstrom’s macroglobulinemia, so some people refer to it as Waldenstrom’s.

To understand WM, it helps to know about the functions of lymphoid tissue in the body.

Lymphoid tissue and the immune system

Lymphoid tissue is made up several types of immune system cells that work together to help the body resist infections. Lymphoid tissue is found in many places in the body:

• Lymph nodes, which are pea-sized collections of immune system cells throughout the body, including in the underarm area, in the groin, on the sides of the neck, and inside the chest and abdomen
• Bone marrow, the soft inner part of certain bones where new blood cells are made
• The thymus, a small organ behind the chest bone and in front of the heart
• The spleen, an organ on the left side of the abdomen next to the stomach
• The tonsils and adenoids in the throat
• Throughout body systems like the digestive system and respiratory system

Lymphocytes (lymph cells) are the main cells of lymphoid tissue. The 2 main types of lymphocytes are:

• B lymphocytes (B cells) respond to an infection by changing into a different type of cell called a plasma cell. Plasma cells make proteins called antibodies (also called immunoglobulins) that help the body attack and kill disease-causing germs like bacteria.
• T lymphocytes (T cells) help direct immune responses, but they also can kill invading germs directly.

Waldenstrom macroglobulinemia

WM is a cancer that starts in B cells. The cancer cells in people with WM are similar to those of 2 other types of cancer: multiple myeloma and non-Hodgkin lymphoma. Multiple myeloma is considered a cancer of plasma cells, and non-Hodgkin lymphoma is a cancer of lymphocytes. WM cells have features of both plasma cells and lymphocytes and are called lymphoplasmacytoid.

WM cells make large amounts of a certain type of antibody (immunoglobulin M, or IgM), which is known as a macroglobulin. Each antibody (protein) made by the WM cells is the same, so it is called a monoclonal protein, or just an M protein. The buildup of this M protein in the body can lead to many of the symptoms of WM, including excess bleeding, problems with vision, and nervous system problems.

The WM cells grow mainly in the bone marrow, where they can crowd out the normal cells that make the different types of blood cells. This can lead to low levels of red blood cells (called anemia), which can make people feel tired and weak. It can also cause low numbers of white blood cells, which makes it hard for the body to fight infection. The numbers of platelets in the blood can also drop, leading to increased bleeding and bruising.

Lymphoma cells can also grow in organs like the liver and spleen, causing these organs to swell and leading to abdominal pain. (For more on the symptoms of WM, see Signs and Symptoms of Waldenstrom Macroglobulinemia.)