In diffuse cutaneous systemic sclerosis, which autoantibody is most characteristic?

• A. Anti-DNA
• B. Anti-Scl-70
• C. Anti-centromere
• D. Anti-RNP

Answer: (B)

Autoantibody profiles in systemic sclerosis help distinguish disease subsets and prognosis. Anti-Scl-70 (topoisomerase I) is most characteristic of diffuse cutaneous systemic sclerosis, and its presence is linked to more extensive skin involvement and a higher risk of interstitial lung disease. In contrast, anticentromere antibodies are more typical of the limited form (CREST) with milder internal organ disease. Anti-RNP antibodies point to mixed connective tissue disease, and anti-DNA antibodies are more typical of systemic lupus erythematosus. Thus, the antibody most characteristic of diffuse cutaneous systemic sclerosis is anti-Scl-70.