SAPHO syndrome mimicking acute osteomyelitis in the lower extremity: A case report

SAPHO (synovitis, acne, pustulosis, hyperostosis, osteitis) syndrome is a rare and often misdiagnosed autoinflammatory condition characterized by an assortment of osteoarticular and dermatological manifestations. We report a case of a 27-year-old female who presented with undiagnosed SAPHO syndrome that mimicked acute osteomyelitis of the 5th digit. The patient had a one-month history of a painful erythematous and edematous 5th digit with intermittent fevers that were recalcitrant to both oral and intravenous antibiotics. Radiographic and advanced imaging displayed inflammatory osteitis, which is commonly seen in cases of osteomyelitis. The patient was referred to rheumatology and diagnosed with SAPHO syndrome. This diagnosis stemmed from the emergence of concurrent symptoms, including anterior chest pain, pustular acne, knee joint pain, and aphthous ulcerations, accompanied by intermittent low-grade fevers. The patient exhibited a notable response to the initiation of Humira, Methotrexate, and Plaquenil therapy. Although she has not fully reached her baseline, there has been a significant improvement in her condition. Our case report underscores the significance of considering atypical rheumatological diseases as potential differential diagnoses in the assessment of patients presenting with symptoms suggestive of chronic, recurrent osteomyelitis, particularly in instances where conventional treatments for infectious causes have proven ineffective.