A 22-year-old man presents with acute nephritic syndrome 10 days after streptococcal pharyngitis. Serum C3 is markedly reduced, C4 is normal. Renal biopsy shows diffuse endocapillary proliferation with 'humps' on electron microscopy and granular IgG and C3 on immunofluorescence. The MOST likely glomerular disease and the expected course are:
- A IgA nephropathy; progressive course requiring immunosuppression
- B Membranoproliferative glomerulonephritis type I; requires complement inhibitor therapy
- C Post-infectious (post-streptococcal) glomerulonephritis; self-limiting with >95% recovery in children ✓
- D Lupus nephritis class IV; requires cyclophosphamide
Explanation
Post-streptococcal glomerulonephritis (PSGN) classically presents 10-14 days after pharyngitis (or 3-6 weeks after impetigo), with nephritic syndrome, depressed C3 (alternate pathway activation) with normal C4, and characteristic 'humps' (large subepithelial immune deposits) on EM. IgG and C3 on IF in a 'starry sky' pattern is typical. Prognosis in children is excellent (>95% complete recovery); adults have slightly worse outcomes. Supportive treatment (antihypertensives, diuretics) is sufficient; immunosuppression is not indicated. MPGN also shows low C3 but is chronic with MPGN pattern on biopsy.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.