13 Sept 2026 · Case #008
Systemic lupus erythematosus (SLE)
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Diagnosis
Systemic lupus erythematosus (SLE)
First-line treatment
Hydroxychloroquine (plus corticosteroids for flares)
How the diagnosis is reached
A malar rash that spares the nasolabial folds is the detail worth pausing on, because that sparing is what separates it from rosacea and seborrhoeic dermatitis, both of which favour exactly the folds lupus leaves alone. Add photosensitivity, inflammatory arthritis, oral ulcers and cytopenias in a young woman and the pattern is systemic lupus. One laboratory oddity supports it further: an ESR of 58 against a CRP of 6 is the classic dissociation of a lupus flare, and a CRP that climbs instead should raise the question of infection rather than disease activity. The antibodies then sort sensitivity from specificity. ANA is positive in almost every patient with lupus and in plenty of people without it, so it rules out rather than rules in; anti-dsDNA and anti-Smith are the specific ones, and anti-dsDNA titres tend to track activity, particularly in the kidney. Low C3 and C4 say complement is being consumed by immune complexes right now. Proteinuria with red cell casts is what makes this urgent rather than merely uncomfortable, since casts mean glomerular inflammation, and it is why a biopsy is planned: the class of nephritis dictates the drug. Hydroxychloroquine is given to essentially everyone regardless of severity, because it lowers flares, organ damage and mortality over years. Corticosteroids cover the flare itself at a dose matched to severity and are tapered as fast as tolerated, since the long-term harm is cumulative. Azathioprine, mycophenolate or belimumab spare steroids in organ-threatening disease, with cyclophosphamide or rituximab held back for severe nephritis or cerebral involvement.
Key clinical clues
- Malar rash sparing the nasolabial folds, worsened by sun exposure
- Inflammatory arthritis and intermittent oral ulcers
- ESR/CRP dissociation with anemia and leukopenia
- Positive ANA plus specific anti-dsDNA and anti-Smith antibodies, with low complement
- Proteinuria and red cell casts suggesting lupus nephritis
The case in full
Presenting complaint
Patient history
A 27-year-old woman presents with six weeks of fatigue, low-grade fevers, and pain and swelling in both wrists and knees. She has also noticed a rash across her cheeks and nose that worsens after sun exposure.
Physical examination
Physical examination
Examination reveals a flat, erythematous rash over the malar area that spares the nasolabial folds, along with mild synovitis of the wrists and proximal interphalangeal joints. She reports having had oral ulcers intermittently, though none are present today.
Initial labs
Laboratory results
A CBC and inflammatory markers are obtained.
| Parameter | Value | Reference |
|---|---|---|
| Hemoglobin | 10.4 g/dLRef 12.0–15.5 | 12.0–15.5 |
| White blood cells | 3.1 ×10⁹/LRef 4.5–11.0 | 4.5–11.0 |
| ESR | 58 mm/hrRef 0–20 | 0–20 |
| CRP | 6 mg/LRef 0–10 | 0–10 |
Autoantibody panel
Laboratory results
An autoantibody panel and complement levels are sent.
| Parameter | Value | Reference |
|---|---|---|
| ANA | Positive, high titerRef Negative (<1:80) | Negative (<1:80) |
| Anti-dsDNA | PositiveRef Negative | Negative |
| Anti-Smith | PositiveRef Negative | Negative |
| C3/C4 complement | LowRef C3 90–180, C4 10–40 mg/dL | C3 90–180, C4 10–40 mg/dL |
Urinalysis
Laboratory results
Urinalysis shows proteinuria and red blood cell casts, raising concern for renal involvement.
Renal workup
Clinical course
A renal biopsy is planned given the urinary findings. Blood pressure is well controlled and there is no evidence of rapidly progressive renal failure at this time.