PSGN (post-streptococcal GN) associated with –
**Core Concept**
Post-streptococcal glomerulonephritis (PSGN) is an immune complex-mediated glomerulonephritis characterized by the deposition of immune complexes in the glomeruli, leading to inflammation and renal damage. This condition typically follows a streptococcal infection, such as strep throat or skin infections.
**Why the Correct Answer is Right**
The characteristic histopathological feature of PSGN is the presence of subepithelial deposits, also known as humps, in the glomerular basement membrane. These deposits are composed of immune complexes, including IgG, IgM, and C3, which are formed in response to the streptococcal antigens. The subepithelial location of these deposits is a hallmark of PSGN and is responsible for the glomerular injury and renal dysfunction seen in this condition. The immune complexes activate the complement system, leading to the formation of C3 convertase and the deposition of C3 and other complement components in the glomeruli.
**Why Each Wrong Option is Incorrect**
**Option B:** PSGN can present with nephritis, but it is not always associated with acute renal failure. While some patients may develop acute renal failure, it is not a universal feature of PSGN.
**Option C:** Low complement levels are more characteristic of membranoproliferative glomerulonephritis (MPGN) and systemic lupus erythematosus (SLE), rather than PSGN. In PSGN, complement levels may be normal or slightly decreased, but not as low as seen in other conditions.
**Option D:** Hypertension and proteinuria can be seen in PSGN, but they are not unique to this condition and can be present in other forms of glomerulonephritis as well. These features are not specific enough to diagnose PSGN.
**Clinical Pearl / High-Yield Fact**
In PSGN, the subepithelial deposits are often described as "humps" due to their characteristic appearance under electron microscopy. This is a key diagnostic feature that differentiates PSGN from other forms of glomerulonephritis.
**Correct Answer:**
✓ Correct Answer: A. Subepithelial deposits