New use for an old treatment: Hydroxychloroquine as a potential treatment for systemic vasculitis.

Antimalarials have been an effective and safe treatment for autoimmune rheumatic diseases such as systemic lupus erythematosus for more than a hundred years. There are surprisingly few reports of hydroxychloroquine use in the systemic vasculitides. Hydroxychloroquine has antithrombotic, cardiovascular, antimicrobial and antineoplastic effects, making it a potentially valuable treatment for patients with systemic vasculitis who are at risk of infections, malignancy and thrombotic events. We report the successful use of hydroxychloroquine in patients with ANCA vasculitis, Henoch Schonlein purpura/IgA vasculitis, Takayasu's arteritis and polyarteritis nodosa. We review the immunomodulatory mechanisms of action of hydroxychloroquine and the existing evidence for its use in the treatment of vasculitis, with a particular focus on ANCA subtypes.