"Synovitis, acne, pustulosis, hyperostosis and osteitis (SAPHO) syndrome": Comment on the article by Zhao et al

We read with great interest the article by Zhao et al.,1 recently published in The Journal of Dermatology, regarding an emblematic case of synovitis, acne, pustulosis, hyperostosis and osteitis (SAPHO) syndrome. We fully agree with Zhao et al., both on the importance of an early diagnosis and on the detrimental consequences of a delayed diagnosis on various aspects of quality of life. In 1987, Chamot and Kahn suggested the acronym SAPHO in order to unify various conditions characterized mainly by the variable association of osteitic ⁄ hyperostotic lesions of the anterior chest wall (ACW) and several skin disorders, such as palmoplantar pustulosis,severe acne and hidradenitis suppurativa. Less commonly described are Sneddon–Wilkinson disease and other neutrophilic dermatoses, namely Sweet syndrome and pyoderma gangrenosum. Inclusion of psoriasis vulgaris as the only skin lesion is still being discussed and should be considered only in patients with a typical sternocostoclavicular hyperostosis.2 We also agree with Zhao et al. that SAPHO syndrome could be underestimated because the cutaneous lesions may be transient, or also absent. Skin manifestations usually precede the onset of osteoarticular complaints, therefore an effort for greater awareness of the ACW pain syndromes is needed among dermatologists. The nosological framing of SAPHO syndrome is still a matter of debate. Although it has repeatedly been related to the spondyloarthropathy family, emerging evidence suggests that SAPHO syndrome could be a primitive inflammatory osteitis, probably related to polygenic auto-inflammatory disorders. Our previous finding of a dysregulation of the extracellular adenosine triphosphate-dependent P2X7–IL1b axis in a case of SAPHO syndrome effectively treated with the interleukin (IL)-1 receptor antagonist anakinra seems to suggest that SAPHO syndrome should be included in the growing family of polygenic auto-inflammatory disorders.3 Different stimuli have been implicated as possible inciting factors, in particular Propionibacterium acnes, either alive or as dead antigen.4 So far, our work, previously published in Arthritis Care & Research, represents the largest published series since the 1980s, with a median follow-up duration of 11 years.5 In agreement with Zhao et al., we found that the course of the disease was variable. In particular, nine patients presented with a limited course lasting less than 6 months but more than 3 months, with a single episode that afterward faded away. In these subjects, no disease flares occurred during a median follow up of 8 years. In 25 cases, after a first, limited course of less than 6 months, the patients experienced multiple remissions and exacerbations. In these patients, the duration of the flares was 2–8 months and they did not demonstrate any apparent periodicity or recurrence. Thirty-seven patients, representing 52% of our series, had a chronic course characterized by fluctuating intermittent periods of exacerbations and short improvements, requiring almost continuous treatment. We also demonstrated that female sex, elevated erythrocyte sedimentation rate and C-reactive protein values, ACW involvement, peripheral synovitis, and the occurrence of two or more skin lesions at the onset are associated with a chronic course. In conclusion, we agree that diagnostic delays are important and that early recognition of SAPHO syndrome is of great importance. Therefore, as Zhao et al. affirmed, we firmly hope that nonrheumatological specialists, such as dermatologists, but also general practitioners and internists, will have greater confidence in recognizing this condition.