Figure 2.

Ultrastructure of endothelial cell injury in the tip and collapsing variant. In the tip lesion of the tip variant (a), swelling of the glomerular endothelial cells (arrow), loss of fenestrae, and effacement of foot processes of podocytes are observed, along with infiltration of macrophages (star). In lesions other than the tip lesion (b), the endothelial damage is relatively mild with maintained fenestrae, mild swelling of the endothelial cells, and hardly detectable widening of the subendothelial space. The collapsing variant (c, d) shows podocyte hypertrophy and vacuolization with expansion of the subpodocyte space (arrowhead) and effacement of foot processes. Narrowed glomerular capillaries (star) are seen with wrinkling of the GBM, indicating collapse of the glomerular capillaries. In the remaining capillary lumens, endothelial cells become swollen (star in d) with irregular loss of fenestra and mild widening of subendothelial spaces. Bar = 10 μm. GBM, glomerular basement membrane.