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Full-House IF Occult Lupus — ESENeph MCQ

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ModerateGlomerulonephritisFull-House IF Occult LupusESENeph

A 40-year-old man presents with nephrotic syndrome and biopsy shows diffuse mesangial and subendothelial immune complex deposits with full-house immunofluorescence (IgG, IgA, IgM, C3, C1q). He has no known history of SLE. What is the most important next investigation?

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Correct answer: D — ANA and anti-dsDNA antibodies plus complement levels – full-house IF strongly suggests lupus nephritis

Full-house immunofluorescence (simultaneous positivity for IgG, IgA, IgM, C3, and C1q) is virtually pathognomonic of lupus nephritis. Even without a prior SLE diagnosis, this biopsy finding mandates serological investigation for lupus (ANA, anti-dsDNA, complement C3/C4, anti-Sm). Up to 15-20% of lupus nephritis cases present as the first manifestation of SLE. The ISN/RPS classification should be applied to determine the LN class.

Reference: KDIGO 2024 – Lupus Nephritis Guideline; ISN/RPS Classification 2018