OSCE — Systemic Lupus Erythematosus

Station instructions (to candidate)

A 24-year-old woman presents to the outpatient department with 6 weeks of joint pain and swelling in both hands, a facial rash that worsens in sunlight, painless mouth ulcers, fatigue and low-grade fever. She has noticed her hair is thinning. Examine and manage.

Vital signs: BP 142/92 mmHg, pulse 88/min, temperature 37.8 C, otherwise stable.

Examiner checklist (assess each — done / partial / not done)

History (2 min)

• Confirms the rash distribution and photosensitivity, and that it spares the nasolabial folds
• Asks about oral/nasal ulcers (painless), alopecia, Raynaud, dry eyes/mouth
• Drug history (hydralazine, procainamide, isoniazid, anti-TNF) and allergies (often sulpha)
• Past history: pregnancy losses, thrombosis, renal disease, family history of autoimmunity

Examination (2 min)

• Inspects skin: malar (butterfly) rash, discoid lesions, livedo, alopecia, and the oral mucosa for ulcers
• Examines the hands for symmetrical non-erosive synovitis and reducible Jaccoud deformities
• Cardiorespiratory: pleural/pericardial rub, effusion
• Screens for organ threat: blood pressure (nephritis), urine dipstick (protein and blood)

Investigations (2 min)

• Bloods: FBC (cytopenias, haemolysis), renal and liver function, ESR/CRP
• Antibodies: ANA (screen), anti-Smith (most specific), anti-dsDNA (activity/renal), C3 and C4 (low in flare)
• Additional: anti-Ro/La, anti-RNP, anti-histone (drug-induced), antiphospholipid antibodies
• Urinalysis and urine protein-to-creatinine ratio; states need for renal biopsy if proteinuria/haematuria
• States the ACR/EULAR 2019 classification (ANA entry + additive weighted score at least 10 with at least one clinical criterion)

Diagnosis (1 min)

• States systemic lupus erythematosus with the multisystem pattern
• Offers a differential: rheumatoid arthritis (erosive, anti-CCP), mixed connective-tissue disease (anti-RNP), drug-induced lupus, vasculitis, infection

Management (2 min)

• Foundation: sun protection, hydroxychloroquine 200-400 mg/day (all patients), smoking cessation, vaccination
• Symptom/flare control: short-course glucocorticoid (e.g. prednisolone 0.5 mg/kg/day) ± steroid-sparing agent
• If lupus nephritis confirmed: induction with mycophenolate mofetil or cyclophosphamide + steroid, then maintenance
• Screens and manages antiphospholipid overlap (aspirin ± anticoagulation)
• Counsels on pregnancy (aspirin + hydroxychloroquine; avoid teratogens; screen anti-Ro) and retinal monitoring on hydroxychloroquine

Key questions to ask the candidate

1. Which antibody is most specific, and which tracks activity? — Anti-Smith is most specific; anti-dsDNA titre (with low C3/C4) tracks activity and nephritis.
2. Why biopsy the kidney here? — New proteinuria/haematuria in SLE needs biopsy to determine the ISN/RPS class (Class IV diffuse proliferative carries the worst prognosis and needs aggressive induction).
3. Why is hydroxychloroquine given to nearly every patient? — It reduces flares, thrombosis, renal involvement and cumulative damage and improves survival; continue in pregnancy; annual retinal screen.
4. Fever in this patient — flare or infection? — Cultures and an infection screen FIRST; treat presumptive infection; only escalate immunosuppression once infection is excluded.

Common errors to flag

• Treating ANA positivity as diagnostic (it is sensitive, not specific; anti-Smith/anti-dsDNA are confirmatory).
• Forgetting to biopsy new proteinuria to classify lupus nephritis.
• Not screening for antiphospholipid antibodies in a patient with thrombosis or pregnancy loss.
• Escalating immunosuppression in a febrile patient without excluding infection first.
• Stopping hydroxychloroquine in pregnancy, or missing the need for retinal screening.
• Overlooking teratogenic drugs (mycophenolate, cyclophosphamide, methotrexate, warfarin) in women of childbearing age.