Waldenstrom macroglobulinemia (WM) is a slow-growing, rare type of non-Hodgkin lymphoma, which is a blood cancer. It occurs in a type of white blood cell called a B-lymphocyte or B-cell. B-cells normally mature into plasma cells whose job is to produce immunoglobulins (antibodies) to help the body fight infections. WM cells have features of both B-lymphocytes and plasma cells (lymphoplasmacytic). Thus, WM is a type of lymphoplasmacytic lymphoma (LPL).
- In WM, there are malignant changes to a B-cell in the late stages of maturation.
- These changes cause the abnormal cell to continue multiplying as a clone of identical cells, primarily in lymph node(s) and, eventually, the bone marrow. These abnormal cells can also buildup in other tissues and organs such as the liver and spleen, causing them to enlarge (hepatosplenomegaly).
- The cancerous cells produce only one type of immunoglobulin, so it is called a monoclonal protein or M protein.
- Almost all people with LPL (90 to 95%) produce monoclonal immunoglobulin M (IgM). Rarely, people with LPL produce other types of immunoglobulins (IgA, IgG) or no immunoglobulins. LPL must be associated with the production of IgM to be diagnosed as WM.
- Because WM makes up the majority of LPL cases, the terms WM and LPL are sometimes used interchangeably.
WM is a rare cancer with only about three to four cases per million people per year or about 1500 new cases diagnosed in the U.S. each year.
WM is often preceded by a condition known as monoclonal gammopathy of undetermined significance of the IgM type (IgM-MGUS). This earliest stage may or may not progress to WM. If IgM-MGUS does progress, it usually does so slowly over time (usually years).
- People with IgM-MGUS have no symptoms but are often identified during routine blood work for a physical examination. There may be a detectable (usually low) amount of abnormal IgM in the blood.
- Once identified, people with IgM-MGUS are monitored with regular exams and lab tests.
- If IgM-MGUS progresses to WM, the abnormal cells can gradually accumulate, generally in the lymph nodes and then the bone marrow.
- If abnormal cells are present and/or increase in the bone marrow and the amount of abnormal M protein increases, then WM is eventually diagnosed. Of those with Ig-M MGUS, about 25% will eventually be diagnosed with WM if they have not already died from some other disease or condition.
- In the early stages of WM, there still may be no noticeable symptoms. This is called asymptomatic or smoldering WM. This condition is typically monitored closely.
- If WM worsens, symptoms may develop, such as fatigue, weight loss, night sweats, fever, recurrent infections, and/or swollen lymph node(s). If this later stage develops, therapy is started to treat symptoms, prevent complications, and manage the disease.