What type of renal pathology is characterized by the fusion of podocytes?

Minimal change disease is characterized by the fusion of podocytes, which are specialized cells that line the glomeruli and play a crucial role in the filtration barrier of the kidneys. In minimal change disease, electron microscopy reveals widespread effacement (flattening) of these podocyte foot processes, leading to a disruption in the normal filtration function. This condition often presents with nephrotic syndrome in children and is typically associated with a good response to corticosteroid therapy.

The selective nature of proteinuria in minimal change disease is due to the loss of charged barrier properties caused by the effacement of podocytes, which decreases the glomerular permeability to larger proteins. This pathology contrasts with other renal conditions, where different mechanisms and cellular changes are observed. For example, in focal segmental glomerulosclerosis, there's varying degrees of podocyte injury but typically not the same effacement across all podocytes. Membranous nephropathy features subepithelial immune complex deposits and a different type of pathology entirely, and diabetic nephropathy is characterized by a distinct set of changes including mesangial expansion and capillary basement membrane thickening rather than podocyte fusion.