How would you approach failure of maintenance therapy (Azathioprine) for PR3 positive, c-ANCA positive, pulmonary–renal vasculitis previously induced with cyclophosphamide, with a history of anaphylaxis to rituximab?  

This is a challenging clinical situation with several appropriate treatment approaches as follows: Desensitization to rituximab - this would need to be done in the ICU but is effective for patients who are willing to undergo the process for whom other maintenance regimen options are suboptimal. Av...