P0433AGE-RELATED DIFFERENCES IN THE SPECTRUM OF BIOPSY-PROVEN GLOMERULONEPHRITIS
Authors: Capusa Cristina-Stela , Pana Nicolae , Popa Otilia , Chiotan Laura , Mandache Eugen , Lipan Mariana , Dumitru Daniela , Mircescu Gabriel 
Published: June 2020

Abstract

Background and Aims
The proportion of geriatric population is increasing globally and age-related changes, as kidney ageing and decline in immunocompetence, might interfere with frequency of various glomerulopathies (GP). Thus, it is conceivable that the spectrum of biopsy-proven GP varies across different age categories. Accordingly, we aimed to describe age-related variation in clinical presentation and the in prevalence of GP diagnosed by kidney biopsy (KB) in adults.

Method
This retrospective study enrolled 1254 subjects selected from the KB database of a large tertiary academic Nephrology center (which provides specialized care for the south-eastern part of our country), over a ten-year span (01.01.2008-31.12.2017). Inclusion criteria were age &gt;18 years, native kidney biopsy, availability of data from light, immunofluorescence, and electron microscopy, and a histologic diagnosis of GP. Repeated biopsies and inadequate tissue samples were excluded. Demographic (age, gender), clinical and laboratory data at the time of biopsy were extracted from medical records for all the selected subjects.
To investigate the possible influence of age on the spectrum of biopsy-proven GP, the cohort was divided into 4 categories: young adults (18 to 30 years, n=156), adults (31 to 64 years, n=868), elderly (65 to 74 years, n=176) and very elderly (≥75 years, n=54), and the collected data were compared by non-parametric methods (Mann-Whitney, Chi2 and Fisher exact tests).

Results
The nephrotic syndrome was the most common presentation form in all age groups but had a higher prevalence in very elderly (62%) and elderly (55%) as compared to adults (37%, p=0.01) and young adults (41%, p&lt;0.001). In the groups below age of 65, the chronic nephritic syndrome was the second most common indication for KB (31% and 28%, respectively), followed by chronic renal failure in adults (13%) and acute nephritic syndrome in young adults (10%).
Lupus nephritis (LN) and IgA nephropathy (IgAN) were the most commonly diagnosed GP in young adults (22% each), followed by minimal change disease (MCD, 14%), membranous nephropathy (MN, 8%), focal and segmental glomerulosclerosis (FSGS, 8%), and thin basement membrane disease (6%). In adults, the most common GP were: IgAN (23%), MN (15%), diabetic nephropathy (DN, 11%) and MCD (10 %).
Conversely, in both the elderly and the very elderly, the most common biopsy-proven GP was MN (26% each). Elderly had renal amyloidosis as the second most prevalent histological diagnosis (17%), followed by DN (11%), and by IgAN and MCD (≈10% each). Crescentic glomerulonephritis (CGN) occurred in 7.5% of the elderly, but it was the second pathology (17%) in subjects aged 75+ years, followed by MCD (15%) and DN (13%). IgAN and amyloidosis were identified in about 5% of this group.
It appears that the prevalence of both clinical presentation and histologically diagnosed GP showed some similarities between the first two and, respectively, last two age categories.

Conclusion
Biopsy-proven GP have different frequencies depending on the patient’s age, with some pathologies predominantly found at older ages (such as membranous nephropathy, amyloidosis and crescentic GN) or, on the contrary, typical for young adults (lupus nephritis and IgAN). These differences account for the distinct clinical presentations at the time of KB.