Waldenstrom's macroglobulinemia is a form of cancer that causes the unrestricted production of B cells. These interfere with the production of red blood cells, which leads to anemia. They also produce immunoglobulin which thickens the blood, making clotting more likely.
It is extremely rare with only about 1,500 cases diagnosed per year in the United States. It can be caused by faults in one of several genes. Care must be taken to do a differential diagnosis to rule out diseases such as multiple myeloma and non-Hodgkin's lymphoma, both of which have similar symptoms.
The disease cannot be cured, but can be treated. However, if the condition is largely asymptomatic, the patient should merely be monitored in the event they start developing symptoms as the treatments are invasive, such as chemotherapy, steroids and plasmapheresis.