Risk of monoclonal gammopathy of undetermined significance: a case-referent study.

A retrospective study was conducted in 285 cases of monoclonal gammopathy of undetermined significance (MGUS) and in 570 sex- and age-matched hospital controls in order to investigate the possible association between socioeconomic status, residence, alcohol and tobacco habits, occupation, occupational exposure to toxic substances, chronic antigenic stimulation, and risk of MGUS. Significant associations with the risk of MGUS were found for farmers (P < 0.005) and for workers in industry (P < 0.025). Occupational exposure to asbestos, fertilizers, mineral oils and petroleum, paints and related products, pesticides, and radiation was significantly (P < 0.05) associated with an increase in risk of MGUS. Chronic immune-stimulating conditions, when considered as a group, presented a significant (P < 0.025) association with the risk of MGUS, but no specific disease has been found to be significantly associated. These data are in agreement with the previous reports on multiple myeloma, suggesting that these factors may play an important role in the development of monoclonal gammopathies. However, these findings need to be confirmed in prospective larger population-based studies.