Waldenström macroglobulinemia (WMG) is a malignant disorder of the bone marrow and lymphatic tissues, a type of lymphoma and characterized by the presence of abnormally large numbers of a particular kind of white blood cell known as B lymphocytes. As these cells accumulate in the body, excessive quantities of an antibody protein known as IgM are produced. Large amounts of IgM cause the blood to become thick (hyperviscosity) and affects the flow of blood through the smaller blood vessels, leading to some of the symptoms of the disorder. Small blood vessels may tear leading to bleeding in the nose, gums, or retina.
