From the Gut to the Bone: A Narrative Review of the Synovitis, Acne, Pustulosis, Hyperostosis, and Osteitis (SAPHO)-Inflammatory Bowel Disease (IBD) Overlap Syndrome.

Synovitis, acne, pustulosis, hyperostosis, and osteitis (SAPHO) syndrome is a rare autoinflammatory disorder primarily affecting the musculoskeletal system and skin. Its coexistence with inflammatory bowel disease (IBD) is uncommon and presents a unique diagnostic and therapeutic challenge, especially when musculoskeletal symptoms precede intestinal involvement. This review synthesizes current literature on the clinical, radiological, and therapeutic intersections between SAPHO syndrome and IBD to provide a comprehensive, multidisciplinary framework that supports early recognition and effective management. A targeted narrative review of published case reports, clinical series, and relevant reviews was conducted using PubMed and Google Scholar, covering literature through 2024. In total, 14 publications describing SAPHO-IBD overlap cases were included in the synthesis, alongside additional literature informing pathophysiology and therapeutic context. Studies describing patients with concurrent SAPHO syndrome and Crohn's disease or ulcerative colitis were included, with extracted data thematically organized to explore disease presentation, diagnostic delays, treatment strategies, and outcomes. The SAPHO-IBD overlap remains underrecognized and is frequently misdiagnosed as spondyloarthritis or infectious osteomyelitis. Diagnostic delays of more than one year were commonly reported across cases, most often due to misclassification. Imaging findings such as the "bull's head" sign and sterile osteitis serve as diagnostic hallmarks but require a high index of clinical suspicion. Biologic therapies, particularly tumor necrosis factor-alpha (TNF-α) inhibitors and Janus kinase (JAK) inhibitors, have shown efficacy across both intestinal and osteoarticular domains; however, treatment challenges persist, including paradoxical dermatologic reactions and variable response across disease compartments. IBD-associated SAPHO syndrome represents a distinct but often overlooked clinical phenotype that challenges conventional diagnostic and therapeutic paradigms. Increased clinical awareness and interdisciplinary collaboration are essential to reduce diagnostic delays and facilitate individualized treatment approaches. While limited by the heterogeneity of case-based evidence and the inherent constraints of narrative review methodology, this synthesis highlights consistent clinical and therapeutic patterns and underscores the need for standardized diagnostic criteria and systematic evaluation of long-term outcomes. To our knowledge, this review is the first to propose a unified clinical and immunopathologic framework specifically addressing SAPHO-IBD overlap.