Transient massive proteinuria associated with Mycoplasma pneumoniae infection

A 5-year-old girl presented with Mycoplasma pneumoniae infection, which was associated with eyelid edema and massive proteinuria. Her clinical manifestations were similar to those of nephrotic syndrome, except for the absence of hypoproteinemia. Light microscopy of renal biopsy tissue showed minor glomerular abnormalities, with no tubulointerstitial changes. Electron microscopy showed sparse fusion of the foot processes, regular nonthickened glomerular basement membrane, and no electron-dense deposits. Immunofluorescent staining of the glomeruli for immunoglobulins (IgG, IgA, IgM) and complement (C3, C4) was negative. Mycoplasma antigen was not detected by indirect immunofluorescence. These findings suggest a causal relationship between M pneumoniae infection and transient renal injury.