Thiopurine methyltransferase enzyme activity
Treatment of granulomatosis with polyangiitis (Wegener’s) is currently viewed as having two phases: induction, where the active disease is put into remission, followed by maintenance.
cyclophosphamide combined with glucocorticoids
rituximab with glucocorticoids.
Before initiation of azathioprine, thiopurine methyltransferase (TPMT), an enzyme involved in the metabolism of azathioprine, should be assayed because inadequate levels may result in severe cytopenia.
The antineutrophil cytoplasmic antibody (ANCA) titer can be misleading and should not be used to assess disease activity.Many patients who achieve remission continue to have elevated titers for years.
A rise in ANCA by itself is not a harbinger of immediate disease relapse and should not lead to reinstitution or an increase in immunosuppressive therapy.