Most common cause of glomerulonephritis?
**Core Concept**
Post-streptococcal glomerulonephritis (PSGN) is a type of acute glomerulonephritis triggered by an immune response to Group A beta-hemolytic streptococci (GABHS) infection. This condition is characterized by the deposition of immune complexes in the glomeruli, leading to inflammation and damage to the kidney tissues.
**Why the Correct Answer is Right**
The correct answer is related to the pathogenesis of PSGN. After a GABHS infection, the immune system produces antibodies against the streptococcal antigens. These antibodies can cross-react with the glomerular antigens, leading to the formation of immune complexes. The immune complexes are deposited in the subepithelial space of the glomerular basement membrane, triggering an inflammatory response and damage to the glomeruli. This process is known as type III hypersensitivity reaction.
**Why Each Wrong Option is Incorrect**
**Option A:** IgA nephropathy is a different type of glomerulonephritis characterized by the deposition of IgA antibodies in the glomeruli, but it is not the most common cause of glomerulonephritis.
**Option B:** Membranous nephropathy is a type of glomerulonephritis characterized by the deposition of immune complexes in the subepithelial space, but it is less common than PSGN.
**Option C:** Focal segmental glomerulosclerosis (FSGS) is a type of glomerulopathy characterized by scarring of the glomeruli, but it is not typically associated with an immune response to GABHS infection.
**Clinical Pearl / High-Yield Fact**
Post-streptococcal glomerulonephritis often presents with hematuria, proteinuria, and hypertension, and is associated with a history of recent streptococcal infection, such as strep throat or skin infections.
**Correct Answer: D.**