What Is New and What Is Next for SAPHO Syndrome Management: A Narrative Review

Abstract

Synovitis-acne-pustulosis-hyperostosis-osteitis (SAPHO) syndrome is a rare disease characterized by a sterile inflammatory osteitis and/or arthritis associated with a wide range of dermatological manifestations, such as acne, palmoplantar pustulosis, and psoriasis. This review, providing up-to-date knowledge on this disease, aims at informing researchers and clinicians to help them program future studies in order to improve patients' care. Due to the vast clinical heterogeneity that characterizes this disease, SAPHO syndrome has received various names; among these, chronic recurrent multifocal osteomyelitis represents the most used one. The various nomenclatures in use also reflect different approaches to its management. Indeed, considering the world-wide distribution and the vast onset age (from children to late adulthood), in addition to the multiform clinical presentation, its diagnosis and treatment are often challenging for clinicians. In this review, we provide valuable insights on SAPHO syndrome, delving into its many aspects: epidemiology, pathogenesis, clinical presentation, diagnosis, and classification. Most importantly, this paper addresses the continuously changing treatment panorama of this disease, from established drugs to newly introduced ones. Furthermore, a peculiar focus regards nonpharmacologic approaches, including traditional Chinese medicine, the apheresis technique, and surgery. Similarly, this review also discusses patients' lifestyle, including quality of life. To improve SAPHO syndrome's management, different knowledge gaps should be filled, such as its current epidemiology and pathogenesis. In turn, perfected knowledge in these fields could also advance research in therapy.

Keywords: SAPHO; SAPHO syndrome; biologics; spondyloarthritis; therapy.

Figure 1

Pathogenesis of SAPHO syndrome. A complex interaction between genetic predisposition, environmental factors, and immune dysregulation leads to the loss of tolerance that, in turn, produces the activation of the immune system. The T helper 17 cells (Th-17) appear to be pivotal in this process. In fact, IL-17 production leads to the typical skin disorders related to psoriasis (together with IL-23) and acne. On the other hand, Th-17 mediates the osteoarticular manifestations, such as peripheral arthritis, and—by activating osteoclasts—bone damage (osteolysis and hyperostosis). Figure legend: IL: interleukin; DC: dendritic cell; Th: T helper cell; RANKL: receptor activator of nuclear factor kappa-Β ligand.