Elderly patients with glomerular diseases and IgA nephropathy
Ageing is associated with a progressive decline in kidney function. Studies have shown that 30% of glomeruli become sclerotic in apparently healthy individuals by age 80. Renal inulin clearance drops by half from 120 mL/min per 1.73 m2 in ages 20s down to 65 mL/min per 1.73 m2 in ages >80 years.3 In the United States, a majority of glomerular diseases in the elderly are secondary to chronic conditions, such as hypertension, diabetes and glomerular ischaemia from diffuse atherosclerotic vascular disease. Primary glomerular diseases have been relatively fewer. However, in patients who undergo kidney biopsy, due to variations in biopsy indication, local biopsy policy and practice style among institutions, the most common glomerular diseases in the elderly, based on the kidney biopsy, have been crescentic glomerulonephritis (GN) associated with ANCA‐mediated vasculitis.4 Similarly, in Europe, the top few kidney diseases from biopsy are crescentic GN, chronic GN, membranous nephropathy (MN) and focal segmental glomerulosclerosis (FSGS).6
The kidney disease spectrum in the elderly based on the kidney biopsy varies between Europe/United States and Asia. A recent large single‐centre study in China showed that about 3% (n = 851) of all biopsies (n = 29 425) in the years 2003–2012 were from patients ≥65 years of age.10 The top four most common biopsy diagnoses were membranous nephropathy (28.8%), diabetic nephropathy (9.8%), IgA nephropathy (9.6%) and vasculitis‐associated crescentic GN (6.8%). Similar results were shown in other studies in China, Korea and Japan.11 The difference in the disease spectrum between the Western and Eastern countries could be due to a true difference in disease distribution and/or due to a variation in the indications and local institutional policies for kidney biopsy. Notably, consistent and common findings across geographical and ethnic differences are, as summarized in a recent paper,15 as follows: (i) MN is the most common biopsy diagnosis if indication for the biopsy is nephrotic syndrome and (ii) crescentic GN associated with ANCA‐mediated vasculitis is the most common diagnosis if the indication is acute kidney injury (AKI).