A 30 year old man presents with generalized edema and hypertension. Urine examination shows subnephrotic proteinuria (<2gm) and microscopic hematuria. Serum complement levels are decreased and he is positive for antihepatitis C antibodies. The most likely diagnosis is –
**Core Concept**
The patient's presentation of generalized edema, hypertension, subnephrotic proteinuria, microscopic hematuria, decreased serum complement levels, and positive anti-hepatitis C antibodies suggests a renal disease associated with hepatitis C virus (HCV) infection, specifically membranoproliferative glomerulonephritis (MPGN).
**Why the Correct Answer is Right**
MPGN is characterized by the deposition of immune complexes and complement activation, leading to inflammation and damage to the glomeruli. HCV infection is a known cause of MPGN, and the presence of anti-HCV antibodies supports this association. The decreased serum complement levels are indicative of complement activation and consumption in the process. The subnephrotic proteinuria and microscopic hematuria are consistent with glomerular damage. The pathophysiology involves the deposition of immune complexes containing HCV antigens, which activate the complement system and attract inflammatory cells, leading to glomerular injury.
**Why Each Wrong Option is Incorrect**
**Option A:** Focal segmental glomerulosclerosis (FSGS) is characterized by sclerosis of segments of glomeruli and is not typically associated with HCV infection or decreased serum complement levels.
**Option B:** IgA nephropathy is characterized by deposition of IgA antibodies in the glomeruli, but it is not typically associated with HCV infection or decreased serum complement levels.
**Option C:** Membranous nephropathy is characterized by thickening of the glomerular basement membrane due to immune complex deposition, but it is not typically associated with HCV infection or decreased serum complement levels.
**Clinical Pearl / High-Yield Fact**
HCV infection is a known cause of MPGN, and screening for HCV antibodies should be considered in patients with unexplained glomerulonephritis.
**Correct Answer: C. Membranoproliferative glomerulonephritis (MPGN)**