Case Report: Rapid improvement with upadacitinib in a case of paradoxical skin lesions associated with SAPHO syndrome.

SAPHO syndrome is a rare autoinflammatory disorder with osteoarticular and cutaneous involvement. Paradoxical skin lesions have been reported during treatment with tumor necrosis factor-α (TNF-α) inhibitors. We describe a 42-year-old man with a 6-year history of SAPHO syndrome presenting with chronic sternoclavicular and lumbosacral pain and sterile pustules on the lower extremities. Conventional therapy with etoricoxib and methotrexate improved musculoskeletal symptoms but failed to resolve skin lesions, while adalimumab treatment led to progressive worsening of cutaneous manifestations. Following a switch to upadacitinib (15 mg once daily), rapid improvement of skin lesions and sustained control of musculoskeletal symptoms were achieved without adverse events. This case suggests that Janus kinase inhibition may represent a therapeutic option for TNF-α inhibitor-induced paradoxical skin lesions in SAPHO syndrome.