What is the hallmark of minimal change disease?

Minimal change disease (MCD) is primarily characterized by podocyte fusion, which is a key histological change observed in this condition. In MCD, light microscopy typically appears normal, which can make diagnosis challenging; however, on electron microscopy, there is notable effacement (fusion) of the podocyte foot processes. This alteration in the architecture of the glomerular filtration barrier is crucial as it leads to increased permeability to proteins, resulting in significant proteinuria, a hallmark clinical feature of the disease.

Podocytes are specialized epithelial cells that play a critical role in maintaining the integrity of the filtration barrier in the kidneys. In minimal change disease, the fusion of these podocyte processes disrupts normal filtration, allowing proteins to escape into the urine, which subsequently leads to the development of nephrotic syndrome.

The other options do not accurately represent minimal change disease. Glomerulosclerosis refers to scarring or hardening of the glomeruli, which is more characteristic of other forms of glomerulonephritis. Intraepithelial lesions and immune complex deposition are features associated more closely with different renal pathologies, such as those seen in lupus nephritis or other forms of glomerulonephritis rather than in minimal change disease.