An 8-year-old boy developed gross hematuria and periorbital edema 12 days after a streptococcal pharyngitis. Serum C3 was low at presentation. He was managed conservatively, but repeat testing 10 weeks later shows C3 remains persistently depressed. This laboratory course argues strongly against resolving post-streptococcal glomerulonephritis and instead suggests:

• A Focal segmental glomerulosclerosis
• B Minimal change disease
• C Anti-GBM disease
• D Membranoproliferative glomerulonephritis ✓

Explanation

Postinfectious glomerulonephritis characteristically lowers C3 transiently, with normalization within 6 to 8 weeks as immune deposits clear. Hypocomplementemia persisting beyond 8 weeks shifts the diagnosis toward MPGN, where alternative pathway activation sustains C3 consumption indefinitely. Biopsy would show lobular accentuation, double contours of the GBM from mesangial interposition, and subendothelial or intramembranous dense deposits. Minimal change disease, FSGS, and anti-GBM disease all run with normal complement levels, excluding them here.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.