Would you have concerns using azathioprine in NXP-2 or TIF-1 gamma positive dermatomyositis patients due to higher risk of malignancy?  

No studies have examined the effect of long-term azathioprine and the risk of malignancy in myositis. However, data from other autoimmune diseases (like lupus, myasthenia gravis, multiple sclerosis) have been negative in most cases (except perhaps for rheumatoid arthritis), and distinct from what is...