Objective: To determine the incidence of immunoglobulin light chain amyloidosis (AL amyloidosis) in a strictly defined geographic area from 1990 through 2015. Patients and Methods: We searched a computerized database for the records of all Olmsted County, Minnesota, residents with a diagnosis of AL amyloidosis from January 1, 1990, through December 31, 2015. In addition, records of all residents with a mention of amyloidosis were obtained from the Rochester Epidemiology Project, which contains the medical records of Mayo Clinic and Olmsted Medical Group. The diagnosis of AL amyloidosis was determined by mass spectrometry, immunohistochemical analysis, or positive Congo red staining. Results: Thirty-five patients were identified as having AL amyloidosis. The median age at diagnosis was 76 years (range, 38-90 years), with men accounting for 54%. The incidence rate of AL amyloidosis from 1990 through 2015 adjusted for age and sex was 1.2 per 100,000 person-years (95% CI, 0.8-1.6 per 100,000 person-years). Rates were similar across the decades 1990-1999, 2000-2009, and 2010-2015 at 1.1, 0.9, and 1.6 per 100,000 person-years, respectively, with no suggestion of an increasing rate during the 26 years. There was a trend toward an increasing incidence over time from 1950 through 2015 in Olmsted County, but it was not significant (P=.15). Applying the rate of 1.2 per 100,000 person-years to the US population of 321 million in 2015, one would expect 3852 new cases of AL amyloidosis in the United States each year. Conclusion: The incidence of AL amyloidosis in Olmsted County has not changed significantly in the past 66 years.
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