Granulomatosis With Polyangiitis: Remissions in a Thiopurine Fast Metabolizer Over 20 Years.

A 35-year-old Maori man presented with lethargy, nasal congestion, scleritis, epistaxis, progressive shortness of breath, myalgia, and pleuritic pain. His CT scan showed bilateral pulmonary infiltrates and a corneal biopsy confirmed granulomatosis with polyangiitis (GPA).  Remission was achieved with cyclophosphamide-based regimen. Maintaining remission proved difficult because of treatment side effects or relapses on cyclophosphamide, methotrexate, or azathioprine maintenance regimes. Overall, he needed six courses of pulse cyclophosphamide / IV methylprednisolone therapy in his first 10 years of treatment. He was identified to be an azathioprine fast metabolizer producing little active metabolite at usual doses. The combination of low dose azathioprine / allopurinol achieved therapeutic level of 6-thioguanine nucleotides (TGNs) to achieve long-term remission. Low dose azathioprine / allopurinol at levels to control inflammatory bowel disease achieve long-term remission of GPA. He has been in remission for 10 years without side effects or relapses.