Dermatology MCQ - Inflammatory Dermatoses - Systemic lupus erythematosus diagnosis

A 25-year-old woman is evaluated for possible systemic lupus erythematosus (SLE). She presents with photosensitivity, oral ulcers, and arthralgias. Which of the following sets of findings, if present, would be sufficient to confer a formal diagnosis of SLE based on the 2019 EULAR/ACR classification criteria?

A. Positive ANA (≥1:80), leukopenia, and proteinuria (500 mg/24h)
B. Fever, positive anti-Smith antibody, and non-scarring alopecia
C. Positive anti-dsDNA antibody, thrombocytopenia, and a history of seizures
D. Positive ANA (≥1:80), class II lupus nephritis on renal biopsy, and Raynaud's phenomenon
E. Positive anti-Ro/SSA antibody, polyserositis, and a malar rash

Correct Answer: C. Positive anti-dsDNA antibody, thrombocytopenia, and a history of seizures

Explanation

The 2019 EULAR/ACR classification criteria for Systemic Lupus Erythematosus require a positive ANA (≥1:80 on HEp-2 cells or an equivalent positive test) as an obligatory entry criterion. Once this is met, points are assigned for clinical and immunologic criteria, with a total score of 10 or more required for classification as SLE.

Let's calculate the score for option C:

• Positive anti-dsDNA antibody: This is an immunologic criterion worth 6 points.

• Thrombocytopenia (<100,000/μL): This is a hematologic criterion worth 4 points.

• History of seizures: This is a neuropsychiatric criterion worth 5 points.

• Total Score = 6 + 4 + 5 = 15 points. This far exceeds the 10-point threshold, confirming the diagnosis.

The other options are incorrect because they either lack the obligatory positive ANA (a requirement not stated in the options but implied by the question's focus on "sufficient...based on the criteria") or do not accumulate enough points.

Why other options are incorrect

• A. Positive ANA (≥1:80), leukopenia, and proteinuria (500 mg/24h):

  • Positive ANA: Entry criterion met.

  • Leukopenia: 3 points.

  • Proteinuria >500mg/24h: 4 points.

  • Total = 7 points. This is below the 10-point threshold.

• B. Fever, positive anti-Smith antibody, and non-scarring alopecia:

  • This option does not state a positive ANA, so it fails the entry criterion. Even if ANA were positive:

  • Fever (non-specific): 0 points in the SLE criteria.

  • Anti-Smith: 6 points.

  • Non-scarring alopecia: 2 points.

  • Total = 8 points. Still insufficient.

• D. Positive ANA (≥1:80), class II lupus nephritis on renal biopsy, and Raynaud's phenomenon:

  • Positive ANA: Entry criterion met.

  • Class II LN (mesangial proliferative): This is a low-grade nephritis and is not assigned points in the 2019 criteria. Only more significant renal pathology (proteinuria, biopsy with class III/IV/V, etc.) scores points.

  • Raynaud's phenomenon: 0 points in the SLE criteria.

  • Total = 0 points. This combination would not classify as SLE.

• E. Positive anti-Ro/SSA antibody, polyserositis, and a malar rash:

  • This option does not state a positive ANA, so it fails the entry criterion. Even if ANA were positive:

  • Anti-Ro/SSA: 3 points.

  • Polyserositis (e.g., pleurisy/pericarditis): 5 points.

  • Malar rash: 3 points.

  • Total = 11 points. This would be sufficient, but the absence of the stated obligatory ANA makes it incorrect in this context.

Key Associations for SLE Diagnosis

• 2019 EULAR/ACR Criteria: This system uses a weighted, points-based approach. The obligatory positive ANA acts as a "gatekeeper." Key high-point criteria include:

  • Renal (up to 10 points): High points for proteinuria, renal biopsy class III/IV/V, or red cell casts.

  • Immunologic (6 points each): Anti-dsDNA, Anti-Smith, Hypocomplementemia.

  • Neuropsychiatric (5-8 points): Delirium, psychosis, seizures.

  • Hematologic (3-4 points): Leukopenia, thrombocytopenia, hemolytic anemia.

• Clinical Significance: These are classification criteria, primarily for research, but they heavily inform clinical diagnosis. A diagnosis of SLE is made clinically by a physician based on the entire presentation, with the criteria providing a structured framework.

• Differential Diagnosis: Includes other autoimmune diseases like Rheumatoid Arthritis, Sjögren's Syndrome, Systemic Sclerosis, Dermatomyositis, as well as chronic infections, drug-induced lupus, and hematologic malignancies.

• Management & Prognosis: Management is tailored to the severity and organs involved. It ranges from antimalarials (hydroxychloroquine for all patients) for mild disease to high-dose corticosteroids and potent immunosuppressants (mycophenolate mofetil, cyclophosphamide, azathioprine, belimumab) for major organ involvement. Prognosis has improved dramatically but is still influenced by the severity of renal, neurologic, and cardiovascular disease.