Frequency of renal disease in Japan: An analysis of 2,404 renal biopsies at a single center

Background: Evaluating the frequency of renal disease according to sex, age, time period and ethnicity is of considerable importance. Methods: Disease frequency was evaluated in a total of 2,404 cases that had undergone a renal biopsy at Tokyo Women's Medical University between 1979 and 2008. Results: The overall frequencies of primary glomerulonephritis (GN) and secondary GN were 77.8 and 14.4%, respectively. Primary GN and nephrosclerosis occurred more frequently among men, while secondary GN was more frequent among women. Primary GN decreased and secondary GN increased with advancing age. Immunoglobulin A nephropathy was the most common form of primary GN during each time period and also gradually increased over time (44.4-57.4%). The most common form of secondary GN was lupus nephritis (59.0%); this disease was commonly observed in women (79.3%) but not as frequently among men (27.9%). Our data regarding the frequencies of each form of primary GN were almost the same as data from other regions of Japan and East Asia but were quite different from data originating in West Asia and South America. Conclusions: Our epidemiological results may be useful for analyzing the morbidity of renal disease.