A patient has a malar rash with joint pain. Which diagnosis is most likely and what autoantibody targets?

A patient has a malar rash with joint pain. Which diagnosis is most likely and what autoantibody targets?

• A. Rheumatoid arthritis; autoantibodies against citrullinated peptides
• B. Systemic lupus erythematosus; autoantibodies attack a wide variety of cells in the body (cell surface, cytoplasm, and nuclear proteins)
• C. Scleroderma; autoantibodies against DNA topoisomerase I
• D. Sjögren's syndrome; autoantibodies against Ro/SSA and La/SSB

Answer: (B)

The idea being tested is recognizing systemic lupus erythematosus from a malar (butterfly) rash with joint pain and linking it to a broad autoantibody response. In SLE, the immune system makes antibodies against a wide array of cellular components, especially nuclear antigens such as DNA, histones, and small nuclear ribonucleoproteins, and these autoantibodies can target cytoplasmic and cell-surface components as well. This breadth leads to immune complex formation and deposition in multiple organs, producing the diverse symptoms seen, including skin findings like the malar rash and inflammatory arthritis. That broad autoantibody profile is what sets SLE apart from diseases with more restricted targets. For example, rheumatoid arthritis is driven by antibodies to citrullinated peptides and mainly affects joints; scleroderma involves antibodies like anti-topoisomerase I with prominent skin thickening; Sjögren’s syndrome features antibodies such as Ro/SSA and La/SSB with sicca symptoms. The combination of malar rash and widespread autoantibody activity most strongly points to SLE.

The idea being tested is recognizing systemic lupus erythematosus from a malar (butterfly) rash with joint pain and linking it to a broad autoantibody response. In SLE, the immune system makes antibodies against a wide array of cellular components, especially nuclear antigens such as DNA, histones, and small nuclear ribonucleoproteins, and these autoantibodies can target cytoplasmic and cell-surface components as well. This breadth leads to immune complex formation and deposition in multiple organs, producing the diverse symptoms seen, including skin findings like the malar rash and inflammatory arthritis.

That broad autoantibody profile is what sets SLE apart from diseases with more restricted targets. For example, rheumatoid arthritis is driven by antibodies to citrullinated peptides and mainly affects joints; scleroderma involves antibodies like anti-topoisomerase I with prominent skin thickening; Sjögren’s syndrome features antibodies such as Ro/SSA and La/SSB with sicca symptoms. The combination of malar rash and widespread autoantibody activity most strongly points to SLE.