Case Report: Successful treatment of SAPHO syndrome refractory to adalimumab with upadacitinib.

Background: Synovitis, acne, pustulosis, hyperostosis, and osteitis (SAPHO) syndrome is a rare autoinflammatory disorder characterized by osteoarticular and cutaneous manifestations. While tumor necrosis factor-alpha (TNF-α) inhibitors such as adalimumab are increasingly used for refractory cases, some patients exhibit inadequate response. Janus kinase (JAK) inhibitors have emerged as a potential alternative, but data on the selective JAK1 inhibitor upadacitinib in SAPHO syndrome are lacking. Case summary: An 18-year-old male presented with a 7-year history of recurrent facial acne since 2016. Whole-body bone scintigraphy revealed focally increased radiotracer uptake in the right clavicle, consistent with SAPHO syndrome. Initial treatment of acne with adapalene gel combined with oral minocycline failed to improve skin symptoms, leading to the decision to ultimately pursue biologic therapy. After four months of adalimumab therapy, the patient initially showed improvement in chest pain and dermatitis but subsequently experienced paradoxical worsening of facial acne accompanied by erythema and pruritus. No improvement was observed after an additional four weeks of continued adalimumab treatment. Following a transition to upadacitinib, facial lesions improved within 4 weeks and achieved marked resolution by 8 weeks. Conclusion: This report of upadacitinib in SAPHO syndrome demonstrates its rapid and substantial efficacy in a patient refractory to adalimumab. Upadacitinib may represent a promising treatment option for difficult-to-treat SAPHO syndrome, particularly in cases with inadequate response to TNF-α inhibition.