Question:
A female presents with malar rash and her serology is positive for ANA and dsDNA antibodies. What is the most likely diagnosis?
A female presents with malar rash and her serology is positive for ANA and dsDNA antibodies. What is the most likely diagnosis?
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Anti-dsDNA and Anti-Smith (anti-Sm) are the two most specific antibodies for SLE. While anti-Sm levels remain relatively constant, anti-dsDNA levels can be used to monitor disease activity and predict renal flares.
Updated On: Sep 3, 2026
- systemic lupus erythematosus (SLE)
- Dermatomyositis
- systemic sclerosis
- Mixed connective tissue disease (MCTD)
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The Correct Option is A
Solution and Explanation
Concept:
The combination of a characteristic clinical sign (malar rash) and highly specific autoantibodies (anti-dsDNA) establishes the diagnosis of Systemic Lupus Erythematosus (SLE).
SLE is a multisystem autoimmune disorder predominantly affecting women of childbearing age, characterized by diverse clinical manifestations and the production of pathogenic autoantibodies.
Explanation:
• The malar (butterfly) rash is a classic acute cutaneous manifestation of SLE. It typically spares the nasolabial folds, helping to distinguish it from rosacea or dermatomyositis.
• Antinuclear Antibodies (ANA) are the best screening test for SLE due to their high sensitivity ($>$95%), though they lack specificity.
• Anti-double-stranded DNA (anti-dsDNA) antibodies are highly specific for SLE. Their titers often fluctuate with disease activity, particularly correlating with the development and severity of lupus nephritis.
• Option (B), Dermatomyositis, presents with a heliotrope rash (violaceous rash over the eyelids, not sparing nasolabial folds), Gottron papules, and proximal muscle weakness. It is associated with anti-Mi-2, anti-Jo-1, and anti-TIF1-gamma antibodies, not primarily dsDNA.
• Option (C), Systemic Sclerosis, is characterized by skin thickening, Raynaud's, and internal organ fibrosis. Associated antibodies include anti-centromere and anti-Scl-70 (anti-topoisomerase I).
• Option (D), Mixed Connective Tissue Disease (MCTD), has overlapping features of SLE, systemic sclerosis, and polymyositis. Its hallmark autoantibody is anti-U1 RNP, and by definition, it typically lacks high titers of dsDNA or Sm antibodies.
Final answer:
The presentation of a malar rash alongside ANA and the highly specific anti-dsDNA antibody definitively points to Systemic Lupus Erythematosus.
The combination of a characteristic clinical sign (malar rash) and highly specific autoantibodies (anti-dsDNA) establishes the diagnosis of Systemic Lupus Erythematosus (SLE).
SLE is a multisystem autoimmune disorder predominantly affecting women of childbearing age, characterized by diverse clinical manifestations and the production of pathogenic autoantibodies.
Explanation:
• The malar (butterfly) rash is a classic acute cutaneous manifestation of SLE. It typically spares the nasolabial folds, helping to distinguish it from rosacea or dermatomyositis.
• Antinuclear Antibodies (ANA) are the best screening test for SLE due to their high sensitivity ($>$95%), though they lack specificity.
• Anti-double-stranded DNA (anti-dsDNA) antibodies are highly specific for SLE. Their titers often fluctuate with disease activity, particularly correlating with the development and severity of lupus nephritis.
• Option (B), Dermatomyositis, presents with a heliotrope rash (violaceous rash over the eyelids, not sparing nasolabial folds), Gottron papules, and proximal muscle weakness. It is associated with anti-Mi-2, anti-Jo-1, and anti-TIF1-gamma antibodies, not primarily dsDNA.
• Option (C), Systemic Sclerosis, is characterized by skin thickening, Raynaud's, and internal organ fibrosis. Associated antibodies include anti-centromere and anti-Scl-70 (anti-topoisomerase I).
• Option (D), Mixed Connective Tissue Disease (MCTD), has overlapping features of SLE, systemic sclerosis, and polymyositis. Its hallmark autoantibody is anti-U1 RNP, and by definition, it typically lacks high titers of dsDNA or Sm antibodies.
Final answer:
The presentation of a malar rash alongside ANA and the highly specific anti-dsDNA antibody definitively points to Systemic Lupus Erythematosus.
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