The cause of macroglobulinemia is unknown. The disease is similar to myeloma in being slightly more common in men and occurring with increased incidence with age (median 64 years). There have been reports that the IgM in some patients with macroglobulinemia may have specificity for myelin-associated glycoprotein (MAG), a protein that has been associated with demyelinating disease of the peripheral nervous system and may be lost earlier and to a greater extent than the better known myelin basic protein in patients with multiple sclerosis. Sometimes patients with macroglobulinemia develop a peripheral neuropathy before the appearance of the neoplasm. There. | Chapter 106. Plasma Cell Disorders Part 9 The cause of macroglobulinemia is unknown. The disease is similar to myeloma in being slightly more common in men and occurring with increased incidence with age median 64 years . There have been reports that the IgM in some patients with macroglobulinemia may have specificity for myelin-associated glycoprotein MAG a protein that has been associated with demyelinating disease of the peripheral nervous system and may be lost earlier and to a greater extent than the better known myelin basic protein in patients with multiple sclerosis. Sometimes patients with macroglobulinemia develop a peripheral neuropathy before the appearance of the neoplasm. There is speculation that the whole process begins with a viral infection that may elicit an antibody response that cross-reacts with a normal tissue component. Like myeloma the disease involves the bone marrow but unlike myeloma it does not cause bone lesions or hypercalcemia. Like myeloma a serum M component is present in the serum in excess of 30 g L 3 g dL but unlike myeloma the size of the IgM paraprotein results in little renal excretion and only 20 of patients excrete light chains. Therefore renal disease is not common. The light chain isotype is kappa in 80 of the cases. Patients present with weakness fatigue and recurrent infections similar to myeloma patients but epistaxis visual disturbances and neurologic symptoms such as peripheral neuropathy dizziness headache and transient paresis are much more common in macroglobulinemia. Physical examination reveals adenopathy and hepatosplenomegaly and ophthalmoscopic examination may reveal vascular segmentation and dilatation of the retinal veins characteristic of hyperviscosity states. Patients may have a normocytic normochromic anemia but rouleaux formation and a positive Coombs test are much more common than in myeloma. Malignant lymphocytes are usually present in the peripheral blood. About 10 of macroglobulins are .
