C1q Nephropathy — ESENeph MCQ

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HardGlomerulonephritisC1q NephropathyESENeph

A 45-year-old woman with SLE develops membranoproliferative pattern on kidney biopsy with C1q-dominant IF staining. What diagnosis should be considered?

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Correct answer: C — C1q nephropathy – a rare entity with dominant/co-dominant C1q staining; may overlap with lupus nephritis but can occur without systemic SLE features

C1q nephropathy is characterised by dominant or co-dominant mesangial C1q staining on IF, often with a proliferative or membranoproliferative pattern on light microscopy. It can overlap with lupus nephritis (which also shows C1q) but may occur in patients without full SLE criteria. Distinguishing C1q nephropathy from lupus nephritis requires clinical correlation (serological lupus markers, extrarenal features). In SLE patients, C1q-dominant staining is typically classified within the lupus nephritis framework. Treatment follows lupus nephritis guidelines if SLE criteria are met.

Reference: KDIGO 2021 – GN Guideline; Vizjak et al 2008 – C1q Nephropathy