## **Core Concept**
The question pertains to the ultrastructural characteristics of glomerular basement membrane (GBM) alterations and deposit locations in various kidney diseases, specifically as observed under electron microscopy. The key features mentioned are "characteristic splitting of GBM" and "subepithelial deposits." These features are critical in diagnosing and differentiating glomerular diseases.

## **Why the Correct Answer is Right**
The correct answer, **Membranoproliferative Glomerulonephritis (MPGN)**, is associated with the characteristic splitting of the GBM due to the interposition of mesangial cells and matrix into the capillary walls, leading to a "tram-track" or "double contour" appearance under electron microscopy. While subepithelial deposits are more typically associated with membranous nephropathy, MPGN can exhibit various patterns of immune complex deposition, including subepithelial, subendothelial, and mesangial deposits.

## **Why Each Wrong Option is Incorrect**
- **Option A: Minimal Change Disease** is characterized by the loss of foot processes of podocytes under electron microscopy but lacks significant GBM splitting and immune complex deposits.
- **Option B: Membranous Nephropathy** features subepithelial deposits but does not typically show GBM splitting.
- **Option D: Diabetic Nephropathy** shows thickening of the GBM and mesangial expansion but not characteristic splitting of the GBM or subepithelial deposits as defining features.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the ultrastructural findings, including GBM alterations and the location of immune complex deposits, are critical in the classification and management of glomerular diseases. MPGN, characterized by GBM splitting and various patterns of deposition, often presents with hematuria, proteinuria, and reduced kidney function, and its management may involve immunosuppression and treatment of underlying conditions.

## **Correct Answer:** . **Membranoproliferative Glomerulonephritis**