**Question:** Most common cause of immune complex associated MPGN in adult population is:

A. Hepatitis C virus infection
B. Human immunodeficiency virus (HIV) infection
C. Systemic lupus erythematosus (SLE)
D. Diabetes mellitus

**Core Concept:** Membranoproliferative glomerulonephritis (MPGN) is a type of kidney disease characterized by damage to the glomerular basement membrane and mesangium, leading to proteinuria, hematuria, and hypertension. Immune complex-associated MPGN occurs when immune complexes are deposited in the kidneys, causing inflammation and tissue damage.

**Why the Correct Answer is Right:** The correct answer is **C. Systemic Lupus Erythematosus (SLE)** because it is a chronic autoimmune disease where immune complexes containing autoantibodies and immune complexes accumulate in various organs, including the kidneys. This leads to inflammation and tissue damage, resulting in immune complex-associated MPGN.

**Why Each Wrong Option is Incorrect:**

A. **Hepatitis C virus infection (HCV)**: Although HCV infection can cause MPGN, it is less common than SLE. Moreover, MPGN in HCV infection is typically immune complex-independent and is characterized by cryoglobulinemia.

B. **Human immunodeficiency virus (HIV)** infection: While MPGN is a known complication of HIV infection, the correct answer is not HIV because immune complex-associated MPGN is more commonly associated with SLE.

D. **Diabetes mellitus**: Diabetes is not the most common cause of immune complex-associated MPGN. Diabetes can lead to diabetic nephropathy, a different kidney disease characterized by nephrinuria and albuminuria, but not MPGN.

**Clinical Pearl:**

In clinical practice, distinguishing between MPGN types is essential for appropriate diagnosis and treatment. SLE-associated MPGN typically responds well to corticosteroids, while other causes, like HCV infection and diabetes, may require different therapeutic approaches.