A 45-year-old woman complains of severe headaches and difficulty in swallowing. Over the past 6 months, she has noticed small, red lesions around her mouth as well as thickening of her skin. The patient has "stone facies" on physical examination. Which of the following antigens is the most common and most specific target of autoantibody in patients with this disease?

Scleroderma (refer to the image below) Autoimmune disease of connective tissue. Antinuclear antibodies are common but are usually present in a lower titer than in patients with SLE. Antibodies viually specific for scleroderma include:- Nucleolar autoantibodies (primarily against RNA polymerase) Antibodies to Scl-70, a non-histone nuclear protein topoisomerase; Anticentromere antibodies (associated with the "CREST" variant of the disease). The Scl-70 autoantibody is most common and specific for the diffuse form of scleroderma and is seen in 70% of patients. -Autoantibodies to double-stranded DNA (choice B) are seen in patients with SLE. -Autoantibodies to SS-A/SS-B are seen in patients with Sjogren syndrome. (Fig: A fibroblastic focus is present at the arrows.) Diagnosis: Scleroderma