True about post streptococcal glomerulonephritis
**Core Concept**
Post-streptococcal glomerulonephritis (PSGN) is an immune complex-mediated glomerulonephritis that occurs after an infection with certain strains of group A beta-hemolytic streptococci (GABHS). This condition is characterized by the deposition of immune complexes in the glomeruli, leading to inflammation and damage to the kidney.
**Why the Correct Answer is Right**
The correct answer is related to the pathophysiology of PSGN. The condition typically follows a streptococcal infection, such as pharyngitis or skin infection, and is mediated by the deposition of immune complexes containing antibodies against streptococcal antigens. These immune complexes activate the complement system, leading to the formation of membrane attack complexes (MACs) and the activation of various inflammatory cells, including neutrophils and macrophages. This results in the characteristic histological findings of PSGN, including crescents, hypercellularity, and the presence of immune complexes.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because PSGN is not primarily caused by a direct bacterial invasion of the glomeruli. While there is some evidence of direct bacterial invasion in some cases of PSGN, the condition is primarily an immune complex-mediated disease.
**Option B:** This option is incorrect because PSGN is not typically associated with the presence of ANCA (anti-neutrophil cytoplasmic antibodies). ANCA is more commonly associated with diseases such as granulomatosis with polyangiitis and microscopic polyangiitis.
**Option C:** This option is incorrect because PSGN is not typically associated with a significant elevation in serum levels of cryoglobulins. Cryoglobulins are more commonly associated with diseases such as mixed cryoglobulinemia.
**Option D:** This option is incorrect because PSGN is not typically associated with a significant elevation in serum levels of rheumatoid factor. Rheumatoid factor is more commonly associated with diseases such as rheumatoid arthritis.
**Clinical Pearl / High-Yield Fact**
It's worth noting that PSGN can occur in individuals who have a history of streptococcal infections, even if they do not currently have an active infection. This is because the immune system can take several weeks to months to clear the streptococcal antigens from the body.
**Correct Answer: C.**