Systemic lupus erythematosus: Viva

Branch 1: Classification

The candidate should classify this as systemic lupus erythematosus using the 2019 European League Against Rheumatism and American College of Rheumatism criteria. The entry criterion is a positive antinuclear antibody at any time, which is met. The weighted score then exceeds the threshold of 10 points: acute cutaneous lupus (the malar rash) scores 6 in the mucocutaneous domain, joint involvement scores 6 in the musculoskeletal domain, low C3 and C4 together score 4, and anti-dsDNA scores 6 in the SLE-specific antibody domain. A strong candidate states that each criterion counts once, the highest within a domain is taken, and a more likely alternative must be excluded. ^[1]

If the examiner presses on the older criteria, the candidate should contrast the 2019 system with the 1997 American College of Rheumatology criteria (at least four of eleven criteria) and the Systemic Lupus International Collaborating Clinics 2012 criteria (at least four of seventeen, with one clinical and one immunological), demonstrating familiarity with the lineage and the move toward weighting by specificity. The candidate should also flag that the urinalysis abnormality mandates renal biopsy, and that a biopsy showing class III or IV lupus nephritis would classify lupus regardless of the point total via the biopsy shortcut. ^[1]