Epidemiology

There appear to be some variation in the prevalence of this disease, based on geography and race. In a study from a small southeastern Minnesota community, M protein was found in 15 of the 1200 adults (1.25%) aged 50 years or older.1 In a study from Sweden, of 6995 adult patients aged 25 years or older, Axelsson reported presence of an M protein in 1%.2 Saleun et al. detected a monoclonal protein in the sera of 334 persons, from among 30,279 French adults studied, translating to a prevalence of 1.1%.3 In a study from Greece, a paraprotein was detected in 75 of the 1564 patients (aged 50-95 years) studied, of whom 60 were classified as having MGUS.4 Among Japanese patients older than 50 years, Kurihara reported the presence of M protein in 71 of 2007 samples (3.5%).5 In a convenience sample of community-dwelling elderly subjects aged 63-95 years seen for health screening examinations, Bowden found an M protein in 2.7% of Japanese, compared to 10% of Americans.6 African Americans have been reported to have a higher prevalence of M proteins compared to that reported in Caucasians.7 In a study of 1732 elderly subjects (>70 years) selected by stratified random household sampling, Cohen found 106 (6.1%) with a monoclonal gammopathy.8 African Americans (8.4%) had a greater than twofold prevalence of monoclonal gammopathy compared to whites (3.8%).

The prevalence of monoclonal gammopathy increases with age, and is greater in men than women.9 In the Japanese study, 11% of those from 80 to 89 years had detectable paraprotein in the sera.5 In the study by

Cohen, the incidence of MGUS among those older than 70 years was 3.6%.8 In a study of residents from a retirement home, the prevalence of monoclonal gam-mopathies was 6% in those younger than 80 years, compared to 14% in those older than 90 years.10 Ligthart et al. reported the presence of M protein among 23% of 439 patients aged 75-84, compared to a control group aged 25-34 years, of whom none had a detectable paraprotein.11 There is a slight preponderance of male gender among MGUS patient populations (Male:Female ratio of 1.1 to 1.2).812-14 A familial occurrence of monoclonal gammopathies has been reported.15

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