Fig. 2

Allograft kidney biopsy findings of fibronectin nephropathy. Light microscopy shows lobular accentuation with marked mesangial expansion, mild mesangial hypercellularity, and variable expansion of glomerular basement membranes by periodic acid-Schiff-positive (A) and silver-negative material (B). Congo red stain is negative (not shown). No necrosis, crescents, segmental sclerosis, glomerular basement membrane spikes or double contours, pseudothrombi or vasculitis are present. By routine immunofluorescence, there is no significant glomerular or extra-glomerular staining for IgG (C), IgA, IgM, C1q, C3 (D), fibrinogen, kappa, or lambda. The negative immunoglobulin and complement staining are confirmed by immunofluorescence performed on paraffin tissue sections after pronase digestion. Ultrastructurally, there are massive mesangial and subendothelial electron dense deposits without evident substructure (E). Fibronectin immunofluorescence stain is positive in deposits (F). Original magnification, × 200 for A and B, × 400 for C, D, and F