Kaposi sarcoma in a patient treated with upadacitinib for rheumatoid arthritis

Upadacitinib is a Janus kinase (JAK) inhibitor that inhibits JAK1. It is approved for rheumatoid arthritis, psoriatic arthritis, atopic dermatitis, and ulcerative colitis. Kaposi sarcoma (KS) is a neoplasm of lymphatic endothelium-derived cells infected by human herpesvirus 8 (HHV-8).1 KS is subdivided into the following 4 clinical variants: classic, African endemic, because of iatrogenic immunosuppression, and associated with AIDS.1 Many immunosuppressants have been reported to trigger KS. To our knowledge, we report the first case of KS induced by upadacitinib.