The incidence and epidemiology of plasma cell neoplasms.

Plasma cell neoplasia includes monoclonal gammopathy of undetermined significance (MGUS), multiple myeloma (MM), and Waldenström's macroglobulinemia (WM). In MGUS, a large, stable clone does not cause symptoms; additional change(s) is/are required to convert this clone into a progressively expanding tumor that becomes symptomatic, as in MM or WM. The prevalence of MGUS (i.e., the number of cases in a defined population at a certain time) is 20 times greater than MM. The incidence (i.e., the number of cases developing in a defined population in a defined period) has not been determined for MGUS. Between 1960 and 1969, the average, annual, age-adjusted (1950 standard) incidence of MM in Malmö, Sweden was 3.4/10(5). The incidence of MM is strongly influenced by the age and race of the population, and the diagnostic services available. MM is a disease of old age; it rarely occurs before the age of 40. The incidence of MM increases rapidly with age, is lowest among the Chinese and Japanese, intermediate among Caucasians in America and Europe, and highest among blacks in the USA. The striking differences in the incidence of MM in different countries appears to be due to racial rather than environmental differences, since the low incidence among the Chinese and Japanese in Asia has migrated with them to the Bay area of California and to Hawaii. The high incidence of MM in USA black males (10.8/10(5)) and females (7.2/10(5)) is more than twice the rate for whites in the same regions.(ABSTRACT TRUNCATED AT 250 WORDS)