Clinical and pathological characteristics in elderly patients with IgA nephropathy

BACKGROUND: Immunoglobulin A nephropathy (IgAN) is the most common cause of primary glomerulonephritis, with highly variable manifestations. Although the peak incidence of IgAN is in young adults, the diagnosis among elderly people is increasing. Here we explored the effect of aging on IgAN features, as well as cellular senescence in the kidney of IgAN. METHODS: A total of 910 patients with IgAN were enrolled, which contained 182 individuals in each age stage (aged ≥60, 50–59, 40–49, 30–39 and 20–29 years). Clinical and pathological manifestations at the time of renal biopsy were compared. Additionally, 38 patients with IgAN (19 aged over or equal to 60 years and 19 aged below 60 years) were randomly selected for p16(INK4a) staining by immunohistochemistry. The percentage of p16(INK4a)-positive cells in glomeruli, renal tubule and interstitium were separately quantified. RESULTS: Compared with young IgAN patients, elderly patients presented with higher levels of circulating IgA, uric acid and proteinuria, but lower estimated glomerular filtration rates (eGFR), as well as lower red blood cell counts, platelet counts and lymphocyte counts. Moreover, elderly IgAN patients showed higher incidence of hypertension, and lower incidence of prodromic infection. Regarding histological lesions in the kidney, young IgAN patients had higher degree of IgA and C3 deposits, while elderly IgAN patients had more severe Oxford-E lesions, but less severe Oxford-S lesions. The percentage of glomerular and tubular p16(INK4a)-positive cells in elderly patients showed an increasing trend, but statistical significance was not reached. The percentage of p16(INK4a)-positive nuclei in renal interstitium was positively associated with T score, while increased percentage of p16(INK4a)-positive nuclei in renal tubule was associated with eGFR and 24-h urinary protein level. CONCLUSION: In our IgAN cohort, elderly IgAN patients presented with some aging-related features, and both aging- and IgAN-induced pathological injury contributed to the kidney lesions in patients with IgAN.