Which disease is primarily associated with foot-process effacement on electron microscopy and normal light microscopy?

• A. Focal segmental glomerulosclerosis
• B. Membranous nephropathy
• C. Minimal change disease
• D. Amyloidosis

Answer: (C)

The key idea is that the problem targets a disease where the damage is primarily to the podocyte foot processes, seen as effacement on electron microscopy, while the glomerular structure looks normal under light microscopy. This pattern fits minimal change disease. In minimal change disease, the glomeruli appear essentially normal on light microscopy, yet electron microscopy reveals diffuse flattening and fusion of the podocyte foot processes, which disrupts the slit diaphragm and allows protein to leak into the urine, causing nephrotic-range proteinuria. This combination—normal light microscopy with podocyte foot-process effacement on EM—is characteristic of minimal change disease and helps distinguish it from other nephrotic syndromes.

By contrast, other conditions would show abnormalities on light microscopy: focal segmental glomerulosclerosis shows sclerosis in some glomeruli under light microscopy; membranous nephropathy reveals thickened capillary walls with immune deposits; and amyloidosis presents with amyloid deposits that are visible with special stains.