Rare Hematologic Disorders: Monoclonal Gammopathy of Undetermined Significance

Monoclonal gammopathy of undetermined significance (MGUS) is a condition in which patients have elevated levels (but less than 3 grams per deciliter) of a specific protein in the blood. As in multiple myeloma, this protein (called M-protein) is produced by plasma cells. In 80 percent of patients with MGUS, however, the protein levels remains constant over time, and symptoms of myeloma do not develop. Some MGUS patients can experience peripheral neuropathy — pain or burning in the extremities.

MGUS is more common than myeloma, occurring in 1 percent of Americans over age 50 and 3 percent over age 70. Each year, in 1 to 2 percent of people with MGUS, the condition will progress to a lymphoproliferative disorder (usually multiple myeloma, less often amyloidosis or Waldenström’s macroglobulinemia).

As long as the abnormal protein level does not rise, MGUS requires no treatment. However, patients should have their serum protein levels monitored regularly. Researchers are investigating ways to prevent MGUS from progressing to multiple myeloma. These approaches include vaccine strategies, thalidomide, and strategies to block plasma-cell survival signals.