**Core Concept:**
Glomerulonephritis is a group of diseases that affect the glomeruli, small clusters of capillaries in the kidneys responsible for filtering blood and maintaining kidney function. The four main types of glomerulonephritis are:

1. IgA nephropathy: IgA is an antibody produced by the immune system, and this type of glomerulonephritis is characterized by immune complex deposition in the glomeruli, leading to inflammation and damage.
2. Membranous nephropathy: This type is characterized by the formation of a thickened basement membrane (membranous thickening) in the glomerulus due to immune complex deposition and subsequent inflammation.
3. Membranoproliferative nephropathy: This type involves both the thickening of the basement membrane (membranoproliferative thickening) and the formation of abnormal immune complexes, resulting in severe renal damage.
4. Focal segmental glomerulosclerosis: This type involves the destruction and scarring of specific areas (foci) within the glomerulus, leading to impaired filtration and subsequent kidney damage.

**Why the Correct Answer is Right:**
The correct answer, Membranous Nephropathy (MN), is characterized by the formation of a thickened basement membrane (membranous thickening) due to immune complex deposition in the glomerulus. This leads to inflammation and damage, resulting in the clinical features mentioned in the question (increased blood pressure, proteinuria, and red blood cell casts).

**Why Each Wrong Option is Incorrect:**
A. IgA nephropathy is characterized by immune complex deposition in the glomerulus, but the basement membrane remains normal, leading to inflammation but not membranous thickening.
B. Membranoproliferative nephropathy involves both membranous thickening and immune complex deposition, making it a more severe disease with more severe clinical features than MN.
C. Focal segmental glomerulosclerosis primarily results in scarring and destruction of specific areas within the glomerulus, leading to impaired filtration but not membranous thickening.

**Clinical Pearl:**
Membranous nephropathy is an important differential diagnosis to consider in patients presenting with nephrotic syndrome (excessive proteinuria), hypertension, and hematuria. A renal biopsy may be necessary to confirm the diagnosis and guide treatment decisions.