**Question:** Spliting of the glomerular basement membrane is seen in -

A. Diabetes
B. Membranous Nephropathy
C. Minimal Change Disease
D. IgA Nephropathy

**Core Concept:**
The glomerular basement membrane (GBM) is a key component of the nephron's filtration barrier, consisting of type IV collagen and other proteins. In various kidney diseases, alterations in the GBM can occur, which may affect the kidney's ability to filter blood effectively. Splitting of the GBM is one of these alterations.

**Why the Correct Answer is Right:**
Splitting of the glomerular basement membrane occurs in conditions characterized by immune complex deposition within the GBM. Membranous nephropathy (MN) is a primary kidney disease where immune complexes containing antibodies and antigens are deposited on the outer side of the GBM, causing it to split. This leads to proteinuria (excess protein loss in urine) and nephrotic syndrome (edema, hypoalbuminemia, and hyperlipidemia).

**Why Each Wrong Option is Incorrect:**

A. Diabetes: In diabetic nephropathy, the primary injury is to the endothelial cells and mesangial cells, leading to thickening of the GBM, but not splitting.

B. Minimal Change Disease (MCD): This is a type of nephrotic syndrome characterized by the absence of immune complex deposition in the GBM. Unlike membranous nephropathy, the GBM remains intact.

C. Minimal Change Disease (MCD): Similar to minimal change disease, MCD involves the loss of podocytes and foot process effacement but does not involve splitting of the GBM.

**Clinical Pearl:** Membranous nephropathy should be considered in the differential diagnosis of nephrotic syndrome, especially when other causes like diabetes or MCD have been ruled out. It is essential to differentiate between these conditions, as the treatment, prognosis, and patient management differ significantly.