**Core Concept**
The loss of foot processes of podocytes is a characteristic histopathological feature associated with certain glomerular diseases. This phenomenon is a result of the disruption of the glomerular filtration barrier, leading to proteinuria. Podocytes, also known as visceral epithelial cells, play a crucial role in maintaining the integrity of the glomerular capillaries.

**Why the Correct Answer is Right**
Lipoid nephrosis, also known as minimal change disease, is a primary cause of nephrotic syndrome in children. The disease is characterized by the loss of foot processes of podocytes, which is a hallmark feature observed under electron microscopy. This loss of foot processes is responsible for the disruption of the glomerular filtration barrier, leading to massive proteinuria. The mechanism underlying this phenomenon is not fully understood, but it is believed to be related to the disruption of the actin cytoskeleton in podocytes.

**Why Each Wrong Option is Incorrect**
**Option A:** Goodpasture syndrome is an autoimmune disease characterized by the presence of anti-GBM antibodies, which target the glomerular basement membrane and the alveolar basement membrane. While it does cause renal damage, the loss of foot processes of podocytes is not a characteristic feature of this disease.

**Option C:** Post-streptococcal glomerulonephritis (PSGN) is an immune complex-mediated disease that occurs after a streptococcal infection. PSGN is characterized by the presence of subepithelial humps and mesangial proliferation, but not the loss of foot processes of podocytes.

**Option D:** Lupus nephritis is a complication of systemic lupus erythematosus (SLE) and is characterized by the presence of immune complexes and vasculitis. While lupus nephritis can cause damage to the glomeruli, the loss of foot processes of podocytes is not a characteristic feature of this disease.

**Clinical Pearl / High-Yield Fact**
The loss of foot processes of podocytes is a specific and sensitive marker for minimal change disease. Electron microscopy is essential for diagnosing this disease, as it allows for the visualization of the characteristic changes in the podocyte foot processes.

**✓ Correct Answer: B. Lipoid nephrosis**