RESUMEN
AIMS: Different patterns of glomerulonephritis (GN) are reported from all over the world and the occurrence of primary GN is changing in the course of time. We report the frequencies of primary GN in a major teaching hospital in Brazil, from 1979-1999. METHODS: The case files of renal biopsies of primary GN were reviewed. The included patients were > 14 years of age, with native kidneys, and the specimens were examined with at least light and immunofluorescence microscopy. We excluded biopsy results of patients with any kind of known secondary glomerular involvement. Differences in proportions of diagnoses between the periods over time were evaluated using Chi-square test for trend. RESULTS: We considered 943 patients for the analysis. Focal and segmental glomerulosclerosis (FSGS) was the most common lesion (n = 279), followed by membranous GN (n = 140), membranoproliferative type I GN (n = 109) and IgA nephropathy (n = 109). FSGS (32.1%) was the most frequent diagnosis among nephrotic patients whereas IgAN (29.4%) predominated in non-nephrotic ones. The occurrence of FSGS increased from the earlier to the later periods: 22.3% (1979-1983), 23.7% (1984-1988), 35.7% (1989-1993), 33.9% (1994-1999), p < 0.05. The increase in frequency of FSGS was proportionally higher in non-nephrotic patients and FSGS became as common as IgA nephropathy in this group (31.6% and 28.0%, respectively) from 1994-1999. CONCLUSIONS: FSGS was the most common pattern of primary glomerulonephritis and its relative frequency seems to be increasing in biopsied patients over time. The reasons for this behavior are unclear and warrant further investigations.