According to the results of a new study in the journal Annals of Hematology, successfully treating H. pylori, a common bacterial infection, does not lead to monoclonal gammopathy of undetermined significance (MGUS) remission.

These results, also supported by other researchers’ work, refute a previous study that suggested H. pylori eradication could cure approximately 30 percent of MGUS cases.

MGUS is an asymptomatic blood disorder characterized by an abnormally elevated level of monoclonal protein, which is often discovered during testing for other disorders. Monoclonal proteins, or “M-proteins,” are produced by plasma cells in the bone marrow.

The presence of M-protein in the blood indicates that plasma cells are proliferating excessively, similar to what occurs in multiple myeloma. However, compared to full-blown myeloma, MGUS shows lower M-protein levels, and the disorder usually causes no symptoms. Each year, however, MGUS carries a one percent chance of transforming into multiple myeloma, and therefore, eradicating MGUS is an important research focus.

In this latest study, researchers treated 30 MGUS patients who were infected with H. pylori with standard antibiotic and antacid therapy. H. pylori, a common bacterial infection of the stomach and gastrointestinal tract, is a primary cause of stomach ulcers and cancer of the stomach lining. Persistent H. pylori infection has also been associated with an increased risk for a certain type of lymphoma, another blood cancer.

At the study’s conclusion, 13 patients were successfully cured of H. pylori, while nine individuals began and stayed infection-free throughout the study. Thirty-three patients, who either refused initial therapy or did not respond to treatment, remained infected with H. pylori. The researchers attributed this particularly low cure-rate to antibiotic resistance, which can be especially prevalent in older patients like the ones treated in this study.

Of the 55 study participants, including the 13 patients who successfully eradicated their H. pylori infection, none experienced MGUS regression. In fact, M-protein levels actually increased in those patients cured of H. pylori infection. A recent, similar study also found no MGUS regression in 15 patients who were successfully treated for H. pylori infection.

“Taking into account that no patient showed a normalisation or even a decrease in [M-protein] levels in the two studies, the residual probability that eradicating H. pylori had a clinically significant effect in MGUS is extremely low,” the study authors explained. “In conclusion, our study adds strength to the previous evidence against the hypothesis that H. pylori eradication might have a beneficial effect on MGUS evolution.”

For more information, see the full article in the August 2009 issue of the Annals of Hematology.