Lupus nephritis and systemic disease: Viva

Branch 1: Classification and the biopsy

The candidate should identify this biopsy as Class IV diffuse proliferative lupus nephritis, the most common and most severe paediatric pattern. The defining feature is proliferative endocapillary and extracapillary change affecting 50 percent or more of glomeruli (65 percent in this case), with subendothelial deposits visible as wire-loop lesions and cellular crescents. A strong candidate should place this in the six-class ISN/RPS 2003 framework: Class I minimal mesangial and Class II mesangial proliferative are mild mesangial-only disease, Class III focal proliferative involves under 50 percent, Class IV diffuse proliferative involves 50 percent or more and is subdivided into IV-S segmental and IV-G global, Class V membranous shows subepithelial deposits with nephrotic-range proteinuria, and Class VI advanced sclerosing shows over 90 percent global sclerosis. The practical divide is proliferative (III, IV) versus non-proliferative. ^[1]

If the examiner presses on the full-house immunofluorescence, the candidate should explain that it means granular staining for all major immunoglobulins (IgG, IgA, IgM) and complement components (C3, C1q), which distinguishes lupus from other glomerulonephritides where the deposition is more restricted (IgA-dominant in IgA nephropathy). The candidate should also explain the activity-versus-chronicity indices: the activity index scores reversible inflammation (crescents, necrosis) and predicts response to immunosuppression, while the chronicity index scores irreversible damage (sclerosis, atrophy, fibrosis) and predicts the long-term outcome. ^[1]