Clinicopathological study of IgA nephropathy in adults: The influence of onset age on clinical and renal histological findings and on the effect of steroid therapy

Abstract

Background. The prognosis of IgA nephropathy (IgAN) varies according to the patient's age. It usually affects children or young adults. However, the onset age for IgAN may be at middle-age or older. The influence of onset age on the clinical and renal histological findings of adult IgAN was investigated. Methods. We selected 39 IgAN patients in whom renal biopsy was performed within 2 years from the onset. The patients were divided into two groups according to onset age; early-onset group (under 35 years; group E) and late-onset group (over 35 years; group L). The clinical and histological findings and the response to steroid therapy were compared in the two groups. Results. (1) Clinically, the levels of proteinuria and hematuria in groups E and L were not different, but the creatinine clearance was lower in group L than in group E. Hypertension was frequent in group L (66.7%), but not in group E. (2) Histologically, the rate of glomerular obsolescence and the grades of interstitial fibrosis and arterio- and arteriolosclerosis were more advanced in group L than in group E. However, there were no differences in the grade of mesangial cell proliferation or mesangial matrix increase, nor were the rates of glomerular crescent and tuft adhesion formation different between the two groups. (3) The reduction of proteinuria and hematuria after 1-year steroid therapy was similar in the two groups. Conclusion. Onset age does not affect the severity of glomerular lesions and the effect of steroid therapy in the early phase of adult IgAN. However, advanced interstitial fibrosis and arterio- and arteriolosclerosis, which may be related to hypertension or the aging process, lead to impaired renal function in late-onset IgAN patients.