Macroglobulinemia (Waldenstrom's macroglobulinemia) is a rare type of cancer that causes overproduction of a type of the antibody (immunoglobulin) IgM. The disease causes the blood to thicken and reduces the body's ability to fight off infection.

Symptoms may not be present in mild cases. In more severe cases, symptoms of macroglobulinemia include weakness and fatigue, recurring infections, problems with thinking and making decisions, shortness of breath, swollen glands, and nerve problems. Treatment may include chemotherapy and a process that removes the antibodies from the blood (plasmapheresis).