This case report describes mogamulizumab-associated Kaposi sarcoma in 2 patients with primary cutaneous T-cell lymphomas.

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Corresponding Author: Emilie Holder, MD, Service de Dermatologie, Hospices Civils de Lyon, Hôpital Lyon Sud, F-69495 Oullins-Pierre-Bénite, France ([email protected]).

Published Online: February 11, 2026. doi:10.1001/jamadermatol.2025.

Conflict of Interest Disclosures: Dr Dalle reported grants from Bristol Myers Squibb, Merck Sharp & Dohme, Pierre Fabre, and Regeneron, and his spouse is an employee of Sanofi outside the submitted work. No other disclosures were reported.