A Case of SAPHO (Synovitis, Acne, Pustulosis, Hyperostosis and Osteitis) Syndrome Complicated by Sweet's Disease

We report the case of a 45-year-old man who had complained of severe acne, left knee pain, sternoclavicular joint pain, and left ankle pain for 5 years. An inflammatory reaction had been observed during a health exam. A month before his presentation at our hospital, he had observed infiltrated erythema on his arms and the dorsum of his hands. On examination, he had infiltrated erythema on the dorsum of his right hand, severe acne on his face, and flares and swelling on his left ankle. A skin biopsy specimen from the erythemic area showed an intense dermal neutrophilic infiltrate. Prednisone therapy was effective, and therefore a diagnosis of Sweet's disease was made. His severe acne and recurrent arthralgia led us to consider the possibility of SAPHO syndrome. Technetium bone scanning showed an increased uptake in the sternoclavicular joint and L2, L3 vertebrae. Therefore, we diagnosed his disease as SAPHO syndrome. Several cases of SAPHO syndrome associated with Sweet's disease have been reported. The pathogenic mechanisms of SAPHO syndrome and Sweet's disease are unclear, but both are neutrophil-related diseases, thus a mechanism involving neutrophils was suggested.