Vanishing Bile Duct Syndrome Caused by a Treatment Regimen Including Avacopan for Microscopic Polyangiitis.

An 81-year-old man was treated with prednisolone, avacopan, and rituximab for microscopic polyangiitis and sulfamethoxazole/trimethoprim (SMX/TMP) and vonoprazan for prophylaxis. The liver enzyme levels were elevated 42 days after avacopan administration. Avacopan, SMX/TMP, and vonoprazan treatment were discontinued. A liver biopsy revealed vanishing bile duct syndrome. The patient was subsequently treated with ursodeoxycholic acid and glucocorticoid. Although vasculitis remained in remission, the patient ultimately died. Autopsy revealed persistent bile ductopenia and progressive liver cell injury confirmed by cytokeratin 7 positivity, severe cholestasis, and portal fibrosis. Further studies are required to elucidate associated mechanisms and risk factors.