Internal Medicine · Year 3 · from Internal Medicine

Case 2: Systemic Lupus Erythematosus

Patient Presentation

A 28-year-old woman presents with 2 months of fatigue, joint pain, and a facial rash. She has noticed the rash worsens with sun exposure. She reports diffuse hair thinning and painful mouth ulcers. She also describes episodes where her fingers turn white then blue in cold weather.

Vital Signs

  • Blood Pressure: 138/88 mmHg
  • Heart Rate: 84 bpm
  • Temperature: 37.6°C

Physical Examination

  • General: Fatigued appearance
  • Skin: Erythematous malar rash sparing nasolabial folds, oral ulcers on hard palate, diffuse non-scarring alopecia
  • Joints: Symmetric polyarthralgia without obvious synovitis (Jaccoud's arthropathy pattern)
  • Cardiovascular: Normal
  • Lungs: Clear

Laboratory Results

  • ANA: 1:640 (positive, homogeneous pattern)
  • Anti-dsDNA: 120 IU/mL (positive)
  • Anti-Smith antibodies: Positive
  • C3: 58 mg/dL (low, normal 90-180)
  • C4: 8 mg/dL (low, normal 10-40)
  • CBC: WBC 3,200/μL, Hgb 10.8 g/dL, Platelets 118,000/μL
  • Urinalysis: Protein 2+, 10-15 RBC/hpf, RBC casts
  • Creatinine: 1.2 mg/dL
  • Spot urine protein/creatinine ratio: 1.8 g/g

Clinical Image

Figure 2: Classic malar (butterfly) rash of systemic lupus erythematosus - erythematous rash over cheeks and bridge of nose characteristically sparing the nasolabial folds.

Image Source: Educational illustration for teaching purposes.

Questions

  1. What clinical and laboratory features support the diagnosis of SLE?
  • A) Positive ANA alone
  • B) Multiple criteria: malar rash, oral ulcers, arthritis, renal involvement, hematologic abnormalities, positive ANA, anti-dsDNA, low complements
  • C) Joint pain only
  • D) Fatigue and fever
  1. What antibodies are most specific for SLE?
  • A) ANA
  • B) Anti-dsDNA and anti-Smith antibodies
  • C) Rheumatoid factor
  • D) Anti-CCP
  1. What findings suggest lupus nephritis in this patient?
  • A) Elevated creatinine only
  • B) Proteinuria, hematuria with RBC casts, low complements, elevated anti-dsDNA
  • C) Positive ANA
  • D) Hypertension alone
  1. What is the next step in management for suspected lupus nephritis?
  1. What are the treatment principles for SLE?

Answers

  1. B) Multiple criteria: malar rash, oral ulcers, arthritis, renal involvement, hematologic abnormalities, positive ANA, anti-dsDNA, low complements - SLICC or ACR/EULAR criteria include:
  • Mucocutaneous: Malar rash, discoid rash, photosensitivity, oral ulcers, alopecia
  • Musculoskeletal: Arthritis
  • Renal: Proteinuria, RBC casts
  • Hematologic: Hemolytic anemia, leukopenia, lymphopenia, thrombocytopenia
  • Immunologic: ANA, anti-dsDNA, anti-Smith, low complements, antiphospholipid antibodies
  1. B) Anti-dsDNA and anti-Smith antibodies - Antibody significance:
  • ANA: Sensitive (>95%) but not specific
  • Anti-dsDNA: Highly specific; correlates with disease activity and nephritis
  • Anti-Smith: Most specific (>99%) but less sensitive
  • Low complements (C3, C4): Indicate active immune complex consumption
  1. B) Proteinuria, hematuria with RBC casts, low complements, elevated anti-dsDNA - Lupus nephritis indicators:
  • Proteinuria (>500 mg/24h)
  • Active urinary sediment (RBC casts = glomerulonephritis)
  • Elevated creatinine
  • Elevated anti-dsDNA (correlates with renal activity)
  • Low complements (active disease)
  • This patient has multiple concerning features
  1. Next step for suspected lupus nephritis:
  • Renal biopsy is essential for:
  • Confirming diagnosis
  • Classifying nephritis (Class I-VI)
  • Guiding treatment intensity
  • Treatment depends on class:
  • Class I-II: May need only hydroxychloroquine and ACE inhibitor
  • Class III-IV: Requires immunosuppression (mycophenolate or cyclophosphamide + steroids)
  • Class V (membranous): Immunosuppression if nephrotic-range proteinuria
  • Also start ACE inhibitor for renal protection
  1. Treatment principles for SLE:
  • Hydroxychloroquine: All SLE patients (reduces flares, mortality, damage)
  • NSAIDs/low-dose steroids: For mild symptoms (arthritis, serositis)
  • Immunosuppressants: For major organ involvement
  • Mycophenolate mofetil (preferred for nephritis induction and maintenance)
  • Azathioprine (maintenance therapy)
  • Cyclophosphamide (severe nephritis, neuropsychiatric lupus)
  • Belimumab: B-cell targeted biologic for active SLE
  • Avoid sun exposure: Photosensitivity triggers flares
  • Monitoring: Regular labs for disease activity and medication toxicity

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