Systemic lupus erythematosus vs Sjögren syndrome and mixed connective tissue disease
How to tell Systemic lupus erythematosus and Sjögren syndrome and mixed connective tissue disease apart when a board question makes them look alike.
SLE is immune-complex multisystem nephritis/rash disease; Sjögren is sicca exocrine disease; MCTD is anti-U1 RNP overlap disease.
Side by side
SLE causes malar/photosensitive rash, oral ulcers, serositis, nephritis, cytopenias, neurologic disease, ANA, anti-dsDNA, anti-Smith, and low complement.
Sjögren causes dry eyes and dry mouth with anti-SSA/SSB and lymphoma risk; MCTD causes overlap features with anti-U1 RNP, Raynaud, swollen hands, and myositis/scleroderma/lupus features.
SLE is immune-complex disease against nuclear antigens with complement activation and multisystem injury.
Sjögren is lymphocytic exocrine gland destruction; MCTD is an overlap autoimmune syndrome centered on anti-U1 RNP antibodies.
Anti-dsDNA, anti-Smith, low C3/C4, proteinuria, and cytopenias support SLE.
Schirmer test, anti-SSA/SSB, salivary gland biopsy, anti-U1 RNP, and Raynaud overlap features support Sjögren or MCTD.
The trap
Autoimmune symptoms overlap, so dryness, nephritis, and overlap antibody pattern separate them.
The repair move
For systemic autoimmune disease, anchor on the dominant organ pattern and signature antibody.
Try a free question
CoreA 36-year-old woman has 6 months of malar rash, photosensitive rash on the chest, painful oral ulcers, polyarthritis, and 1 episode of pleuritic chest pain. Labs: ANA 1:1280, anti-dsDNA positive at 240 IU/mL, anti-Smith positive, C3 64 (low), C4 11 (low). Urine protein/creatinine ratio is 0.5. Which diagnosis is most likely?
Show answer and explanation
Answer: A. Systemic lupus erythematosus. SLE is multisystem disease with rash, oral ulcers, serositis, nephritis, and characteristic anti-dsDNA/anti-Smith positivity with hypocomplementemia.
Why the other choices are tempting
- B. Sjögren syndrome features sicca symptoms (dry eyes/mouth) with anti-SSA/SSB rather than nephritis with anti-dsDNA.
- C. MCTD has overlapping features and high titers of anti-U1 RNP but typically lacks anti-dsDNA/anti-Smith.
- D. RA is erosive symmetric arthritis without rash, oral ulcers, or low complement.
- E. Dermatomyositis has heliotrope rash and proximal muscle weakness with elevated CK.
Flashcards
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What antibodies support SLE?
Anti-dsDNA and anti-Smith support systemic lupus erythematosus.
What symptoms support Sjögren?
Dry eyes and dry mouth support Sjögren syndrome.
Quick answers
What is the fastest way to tell Systemic lupus erythematosus from Sjögren syndrome and mixed connective tissue disease?
SLE is immune-complex multisystem nephritis/rash disease; Sjögren is sicca exocrine disease; MCTD is anti-U1 RNP overlap disease.
What is the key clue for Systemic lupus erythematosus?
SLE causes malar/photosensitive rash, oral ulcers, serositis, nephritis, cytopenias, neurologic disease, ANA, anti-dsDNA, anti-Smith, and low complement.
What is the key clue for Sjögren syndrome and mixed connective tissue disease?
Sjögren causes dry eyes and dry mouth with anti-SSA/SSB and lymphoma risk; MCTD causes overlap features with anti-U1 RNP, Raynaud, swollen hands, and myositis/scleroderma/lupus features.
What is the common trap with Systemic lupus erythematosus vs Sjögren syndrome and mixed connective tissue disease?
Autoimmune symptoms overlap, so dryness, nephritis, and overlap antibody pattern separate them.