Avacopan in the treatment of relapsing polychondritis with myeloperoxidase-antineutrophil cytoplasmic antibody associated vasculitis: A case report.

Background: This case report describes myeloperoxidase-anti-neutrophil cytoplasmic antibody associated vasculitis with kidney involvement in a patient with relapsing polychondritis, which was successfully treated with Avacopan. Although relapsing polychondritis has been associated with anti-neutrophil cytoplasmic antibody-associated vasculitis, overlap can result in severe organ involvement, particularly renal damage progressing to end-stage kidney disease. This case presents a unique opportunity to evaluate the potential role of Avacopan as an alternative therapeutic option in managing myeloperoxidase-anti-neutrophil cytoplasmic antibody-associated vasculitis in the context of relapsing polychondritis highlighting a positive renal response despite treatment challenges.

Case summary: This is a case of a 69-year-old Caucasian woman who presented to our hospital's emergency department with a 4 week history of inflammatory polychondritis affecting the auricular cartilage, accompanied by acute kidney injury. On admission, serum creatinine was elevated at 4.0 mg/dL, which progressively increased to 6.07 mg/dL on day 6. The renal biopsy revealed necrotizing and crescentic glomerulonephritis affecting more than 50% of the glomeruli. She was treated with a total of 2500 mg intravenous methylprednisolone over 3 days followed by oral prednisone. Induction treatment included intravenous cyclophosphamide induction, with plans for a total of 2 doses followed by transition to rituximab. However the patient was unable to tolerate rituximab due to allergic reaction so intravenous cyclophosphamide was continued for a total of 6 doses (cumulative dose 3000 mg). In the setting of persistent acute kidney injury, Avacopan was added to the regimen 3 months after diagnosis. Maintenance therapy included azathioprine in addition to Avacopan. Prednisone gradually tapered off at 6 months.

Conclusion: Avacopan may be beneficial in treating anti-neutrophil cytoplasmic antibody-associated vasculitis with coexisting relapsing polychondritis, especially in cases where preservation of kidney function is critical. Further research will be essential to validate these findings and refine treatment protocols for such complex cases.