Explanation:
This patient has ANCA positive microscopic polyangiitis and is in a clinical remission, with residual proteinuria and renal impairment. The remission has been induced with sequential cyclophosphamide and azathioprine therapy and the only outward manifestation of possible continued “activity” of disease is a positive ANCA serology. While persistence of positive ANCA serology, despite clinical remission may herald a clinical relapse in some patients many exceptions to this finding have been described. Most experts agree that it is better to carefully follow patients with clinically quiescent disease who are serologically positive and to reinstitute therapy at the first sign of a clinical relapse, rather than to expose patients to unnecessary and potentially toxic therapy, based solely on a serologic finding, which may represent a “false positive” with respect to “active” disease. Nevertheless, patients who are serologically “active” may be at increased risk of relapse, especially when they develop an intercurrent infection. Prophylactic trimethoprim-sulfamethoxazole may reduce the likelihood of a recrudescence of pulmonary angiitis, but seems to be less effective in preventing renal relapses. Mycophenolate mofetil may be effective as maintenance therapy in this situation, but prospective studies have not yet been conducted to test this point.
