Glomerular lesions in patients with asymptomatic persistent and orthostatic proteinuria discovered on routine medical examination

Abstract

The incidence of asymptomatic proteinuria in young healthy men entering the army service in Singapore of 0.94%; intermittent orthostatic proteinuria was seen in 0.56% and 0.38% had with persistent proteinuria. Renal biopsies from 45 cases with persistent proteinuria and 10 cases with orthostatic proteinuria were studied by light microscopy, electron microscopic and immunofluorescent antibody techniques. Three cases with orthostatic proteinuria showed a minimal lesion ('Nil') and 7 a minimal lesion with increased centrilobular mesangial matrix and mild focal and segmental mesangial hypercellularity. Focal and segmental capillary loop changes were seen in 2 cases. No immunoglobulin deposits were found in orthostatic proteinuria. A raised anti streptolysin O titer was found in 3 cases. Of the cases with persistent proteinuria 13.3% showed a minimal lesion ('Nil') 66.6% a minimal lesion with increased centrilobular mesangial matrix and mild focal and segmental mesangial hypercellularity: Focal global sclerosis, focal segmental glomerulonephritis and diffuse proliferative GN (mesangial hypercellularity) were each found in 6.7% of patients in this group. Focal and segmental changes in capillary loops were found in 30% of cases. Changes in visceral epithelium such as the appearance of cytoplasmic swelling, vesicles and dense aggregates, and areas of focal foot process fusion were common findings. Mesangial deposits of IgA were found in 34.3% with an IgA IgG β1C globulin combination in 28.6% of cases. IgM β1C globulin was present in 5.7% of cases with persistent proteinuria. Early complement components, C1q and C4, and IgA secretory piece were absent. A raised antistreptolysin O titer was found in 25% of cases. The changes in the glomeruli may represent the end or healing stages of an early bout of glomerulonephritis. Changed hemodynamic response on assuming an upright position may play a role in the loss of protein across the glomerular basement membrane in patients with orthostatic proteinuria.