This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Other Autoimmune Disorders, Subject name: Pathology
Anti-topoisomerase I is marker of: 
Select and explain. 
A. Systemic sclerosis, B. Classic polyaeritis nodosa, C. Nephrotic syndrome, D. Rheumatoid ahritis
A: Systemic sclerosis
Answer: A: Systemic sclerosis 
Explanation: Two ANAs strongly associated with systemic sclerosis are as follows:- One of these,directed against DNA topoisomerase I (anti-Scl 70), is highly specific. Patients who have this antibody are more likely to have pulmonary fibrosis and peripheral vascular disease. The other, an anti-centromere antibody, is found in 20% to 30% of patients, who tend to have the CREST syndrome.