Epidemiology of primary glomerulonephritis in the elderly. Report from the Italian Registry of Renal Biopsy

Background: In the pre-biopsy era, primary glomerulonephritis (GN) was thought to pertain to children and adults. On the contrary, as renal biopsy came into clinical practice, this disease was recognized to affect the elderly too, even if the rate of such an occurrence still had to be defined. Recently, the Italian Registry of Renal Biopsy provided the opportunity to ascertain the diffusion of elderly GN in epidemiological terms. Methods: Eighty-eight per cent of the Italian Renal Units known to routinely perform renal biopsy reported the records of patients who underwent biopsy investigation in 1996. Thus, 2,511 cases were ranked according to patient's age, histological diagnosis and clinical manifestation. The age-related incidence of each clinicopathological picture was calculated as the ratio between the number of patients found to be affected during the year and the number of subjects at risk, namely all age-matched people living in Italy in the same year. Results: A diagnosis of primary GN was found in 1,474 records. Elderly patients accounted for 19% of those biopsy proven primary GN, though elderly people were only 16% of the Italian population. This disproportion indicated that the incidence of primary GN in the elderly was higher than expected: actually, when compared to the incidence in the adult, it was 30.8 vs. 28.3 cases per million of population (PMP). Four histological pictures were found to be more frequent in the elderly than in the adult: membranous GN (13.4 vs. 4.2 PMP), crescentic GN (3.1 vs. 0.9 PMP), membranoproliferative GN (2.9 vs. 0.4 PMP), acute post-streptococcal GN (0.9 vs. 0.4 PMP). As for clinical manifestations, all GN-related symptoms were more frequent in the elderly than in the adult, except one: urinary abnormalities (4.5 vs. 14.1 PMP). Conclusion: Through the Italian Registry of Renal Biopsy, primary GN was found to occur more frequently in the elderly than in the adult. Such a high incidence would be even higher if aged patients showing urinary abnormalities regularly underwent renal biopsy. As this result reverses all previous views, many issues about elderly GN should be reconsidered.