S4890 Infliximab-Induced Synovitis, Acne, Pustulosis, Hyperostosis, Osteitis Syndrome

Introduction: Synovitis, acne, pustulosis, hyperostosis, osteitis (SAPHO) syndrome is a sporadic disease with unknown incidence, characterized by comorbid synovitis, acne, pustulosis, hyperostosis, and osteitis. Clinically, it manifests as an osteoarticular syndrome involving the anterior chest wall along with a cutaneous constellation of psoriasis vulgaris, acne, and palmoplantar pustulosis. In this report, we describe a case of infliximab-induced cutaneous SAPHO syndrome. Case Description/Methods: A 21-year-old woman with a history of partially controlled perianal fistulizing Crohn's colitis on infliximab and alopecia areata presented with progressive hair loss, acne, and generalized body rash, including the genitalia. Her symptoms started roughly 4 months after the infliximab dose escalated to Q4 weeks due to inadequate drug level. Dermatology evaluation with a biopsy of the lesions favored infliximab-induced pustular psoriasis, and the patient was transitioned to upadacitinib. One month later, she had a recurrence of a similar rash with progressive hair loss, polyarticular joint pain, and worsening pustular skin lesions of the perineum, chest, and extremities while her Crohn's colitis was in remission. She reported associated chest pain, insomnia, and decreased oral intake. She failed a trial of risankizumab and cyclosporine but later switched to Spesolimab and methotrexate with rapid improvement in her cutaneous symptoms. Her unique presentation was suggestive of SAPHO syndrome, likely triggered by infliximab escalation. Discussion: Infliximab is an anti-tumor necrosis factor antibody used as a first-line treatment in severe phenotypes of Crohn's Disease and psoriatic arthritis. Commonly reported adverse events include neutropenia and infusion-related adverse reactions. We report a case of SAPHO syndrome as a likely adverse event from infliximab. Due to the rarity of this syndrome, there are no established guidelines for treatment. We identified 1 other case report of SAPHO syndrome, in which the patient presented 3 months after the initiation of infliximab. In this case, the patient showed some improvement following the discontinuation of infliximab. Interestingly, other studies suggest that infliximab can treat osteoarticular manifestations of SAPHO syndrome, which adds complexity to understanding this rare phenomenon. Furthermore, our patient responded favorably to Spesolimab, an FDA-approved anti-IL36R used to treat pustular psoriasis. Taken together, this suggests that SAPHO syndrome may be an autoimmune process defined by 2 distinct pathophysiologies.