SAPHO syndrome: clinico-rheumatologic and radiologic differentiation and classification of a patient sample of 86 cases

Abstract

Synovitis (inflammatory arthritis), acne (pustulosa), pustulosis (psoriasis, palmoplantar pustulosis), hyperostosis (acquired), and ostitis (bland osteomyelitis) are symptoms forming the acronym SAPHO, which is a syndrome of nosologic heterogeneity. All entities forming the SAPHO syndrome are connected by a non-obligate dermatoskeletal association with an aseptic pustulous character. 86 cases were analyzed clinically, radiologically and by histology/histopathology. 31 adult patients showed the typical triad of pustulosis palmo-plantaris (psoriatica, PPP), sterno-costo-clavicular hyperostosis (SCCH), and "productive" spondylopathy, which we define as entity I. spondarthritis hyperostotica pustulopsoriatica (Spond.hyp.pp). Twelve adolescent and 13 adult patients showed entity no. II: chronic recurrent multifocal osteomyelitis (CRMO), being characterized by non-purulent osteomyelitis of plasma-cell sclerotic type, potentially being a reactive inflammatory process. 50% of the adult patients with CRMO showed PPP. Differentiation between these two entities is possible by detection of ossifying enthesiopathy in cases of Spond. hyp.pp and primarily chronic osteomyelitis in cases of CRMO. Two more entities or abortive forms of group I and II are III: the inflammatory syndrome of the anterior chest-wall (ACW syndrome) and IV: the more productive form of isolated sterno-costoclavicular hyperostosis (SCCH). Both are connected quite frequently to HLA-B-27-independent forms of spondarthritis and to pustulous dermatosis. More rarely we find osteo-articular symptoms in cases of acne pustulosa, which form group V: acne-associated spondarthritis and CRMO in the case of acne. Adult forms of CRMO with different forms of appearance (lumosacro-iliac hyperostosis with retroperitobeal fibrosis, pelvic type with affection of the hip-joint) are described. The immunologic theory of a "reactive osteomyelitis" potentially triggered by saprophytes is described. The inverse acne triad is brought in a context of skin symptoms. A case of intercurrent postpartum symptoms together with ulcerative colitis is described. Three cases of patients with Crohn's disease are described. Clinical features, radiological findings, and histopathological elements are brought together to determine the connections between the different entities and the possibilities of differentiation. With these elements together with bone-scan, it is often not necessary to obtain a bone specimen. Therapeutical possibilities, especially concerning CRMO, are discussed. "SAPHO syndrome" is more a sign-post on the way to a more subtle diagnosis when it comes to hyperostotic, skin-associated diseases, and it needs interdisciplinary work to clear the situation.