Renal Relapse in Myeloperoxidase (MPO)-ANCA-Associated Vasculitis

Introduction: Microscopic polyangiitis (MPA) is a small-vessel vasculitis characterized by MPO-ANCA positivity and often presents in renal decline. Recognizing relapses can be challenging when symptoms are mild or nonexistent. We present a case of MPA with new kidney failure present after a remission period to highlight the diagnostic challenges of MPA. Case Description: A 47-year-old woman with a history of pulmonary renal MPA was diagnosed in 2007 after presenting with hemoptysis and hematuria. She had renal relapses in 2013 and 2016. Upon presentation, the patient did not have any clinical symptoms. A month later, she presented with a creatinine of 2.3mg/dL and proteinuria of 1.6g. Urinalysis depicted rising serum creatinine, proteinuria, and hematuria. Her MPO titers were elevated (28.9) and CT chest showed alveolar hemorrhage. Treatment included empiric pred 40 mg/day to monitor vasculitis flare vs AIN while awaiting biopsy. Patient responded to steroid treatment with severe psychiatric side effects. Kidney biopsy revealed severe anca vasculitis. She was later admitted to the hospital and given a lower steroid dose due to previous side effects. Patient was started on immunosuppression and adjunctive steroid sparing therapy. Discussion: Because there were no typical symptoms seen, the escalation of care was not indicated, showing the need to be vigilant in patients with MPA history. Biopsy was conducted due to unexplained relapse with pathology confirming need for immunosuppression. This case underscores the challenges of managing MPA due to patient-specific tolerances as well as the need for biopsies when serologies and signs are inconclusive.Figure shows creatinine trends across flaresFigure shows sediment changes with activity