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PSGN Complement Recovery — ESENeph MCQ

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EasyGlomerulonephritisPSGN Complement RecoveryESENeph

A 28-year-old man presents with haematuria and mild proteinuria 3 weeks after a streptococcal pharyngitis. C3 is low, C4 is normal. What is the expected complement trajectory if this is post-streptococcal GN?

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Correct answer: E — C3 normalises within 6-8 weeks; persistent low C3 beyond 12 weeks should prompt investigation for alternative diagnoses

In post-streptococcal GN, C3 is activated via the alternative pathway (low C3, normal C4). C3 typically normalises within 6-8 weeks. If C3 remains low beyond 12 weeks, alternative diagnoses should be considered: C3 glomerulopathy, membranoproliferative GN, lupus nephritis, or endocarditis-associated GN. Persistent hypocomplementaemia is a key red flag requiring further investigation including repeat biopsy if necessary.

Reference: KDIGO 2021 – Glomerular Disease Guideline; Sethi et al 2012 – Complement in GN