Background/Purpose: SAPHO (synovitis, acne, pustulosis, hyperostosis, and osteitis) is a relatively rare and often underdiagnosed inflammatory disorder. Its diagnosis can be challenging due to its wide range of osteoarticular and cutaneous manifestations. Managing SAPHO syndrome often necessitates a multidisciplinary approach, considering its diverse manifestations across multiple systems. Given the rarity of SAPHO syndrome, treatment approaches are primarily informed by observational studies and case reports. In this study, we present a series of five patients diagnosed with SAPHO syndrome and highlight the distribution of lesions and their response to various therapeutic agents.

Methods: In our retrospective single-center study, we examined SAPHO patients under rheumatology care from 2018 to 2023. We screened patients aged 18 or older using specific ICD-10 codes related to sacroiliitis, sternoclavicular joint pain, inflammatory spondylopathy, inflammatory arthritis, acne vulgaris, hidradenitis suppurativa, pustulosis, palmar pustulosis, and palmoplantar pustulosis. Patients with alternate diagnoses or lost to follow-up were excluded. Our analysis identified a cohort of five SAPHO patients and thoroughly characterized their articular and dermatologic manifestations. Additionally, we evaluated the treatment responses in these patients.

Results: We conducted a study on five patients (four female, one male) with SAPHO syndrome, with a mean age of 49 years (range 28-68). The average follow-up period was 56 months (range 21-130). Among the patients, three (60%) exhibited sternoclavicular joint involvement, while one (20%) had sacroiliitis. Peripheral joint involvement was reported in two patients (40%). Acne was present in three patients (60%) in the arms and legs, while one patient (20%) had hidradenitis suppurativa. One patient (20%) had comorbid Crohn’s disease. All five patients (100%) were treated with methotrexate, with three patients (60%) also receiving adalimumab and one patient (20%) receiving infliximab. Four out of five patients (80%) showed improvement in bone lesions with methotrexate. Skin lesions improved in two patients (40%) with methotrexate and in two patients (40%) with adalimumab. In one patient, infliximab was initiated when adalimumab failed to improve the skin lesions, resulting in improvement. Three patients (60%) required treatment with two or more agents.

Conclusion: In our study, the most frequent involvement observed was in the sternoclavicular joints, followed by peripheral joints and the lower back. Acne was more commonly reported than hidradenitis suppurativa. We found that bone lesions showed favorable responses to treatment with methotrexate, while a significant proportion of skin lesions also demonstrated positive results. Adalimumab was effective in treating skin lesions, except in one case where infliximab proved to be more effective. It is important to note that the lack of validated response criteria specific to SAPHO syndrome currently hinders the objective assessment of therapeutic response. Further research is needed to develop better methods for evaluating the response to various treatment modalities in SAPHO patients.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/unmasking-sapho-a-case-series-revealing-the-clinical-spectrum-and-treatment-approaches/