A 35-year-old man presents with hematuria, proteinuria, and hypertension. Serum complement (C3) is low acutely but returns to normal within 8 weeks. Renal biopsy shows mesangial and subendothelial deposits with a 'lumpy-bumpy' granular IgG/C3 pattern on immunofluorescence. The most likely diagnosis is:

• A Membranoproliferative glomerulonephritis type I
• B Dense deposit disease (MPGN type II)
• C Lupus nephritis class IV
• D Post-infectious (post-streptococcal) glomerulonephritis ✓

Explanation

Post-streptococcal GN classically presents 1-3 weeks after streptococcal pharyngitis or skin infection with nephritic syndrome, transiently low C3, and granular 'lumpy-bumpy' IgG/C3 deposits (subepithelial 'hump' deposits) on EM. Complement normalises within 6-8 weeks, supporting this diagnosis. MPGN type I has persistently low C3 and a tram-track pattern on LM. Dense deposit disease (MPGN II) involves C3 nephritic factor and shows ribbon-like dense deposits on EM. Lupus nephritis IV would show full-house immunofluorescence.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.