A case of diffuse sclerotic osteomyelitis of the mandible associated with SAPHO syndrome successfully treated with an oral bisphosphonate

The SAPHO syndrome (synovitis, acne, pustulosis, hyperostosis, osteitis) is a rare syndrome, which is characterized by osteoarticular and dermatological symptoms. Its etiology remains unclear. Treatments such as non-steroidal anti-inflammatory drugs (NSAIDs) and steroids have been reported, but it is difficult to manage SAPHO syndrome perfectly. Recently, the effectiveness of intravenous bisphosphonates has been reported in many cases. But serious side effects of intravenous bisphosphonates have also been reported in some cases. Intravenous bisphosphonates are known to have more severe side effects than oral bisphosphonates. We therefore hesitated to administer bisphosphonates for diffuse sclerotic osteomyelitis of mandible (DSOM) associated with SAPHO syndrome. However, we considered the possibility that oral bisphosphonates might be suitable for the treatment of SAPHO syndrome, and decided to start administration of oral bisphosphonates. An oral bisphosphonate (alendronate 35 mg/week) was started and continued for 38 weeks. The pain of mandible decreased after 13 weeks of oral therapy and disappeared after 33 weeks, at which administration was ceased. In addition, 99mTc bone scan showed decreased uptake in the left part of the mandible. The patient has made good progress and it has passed for 202 weeks without relapse. To the best of our knowledge, this is the first reported case of successful treatment of DSOM associated with SAPHO syndrome with an oral bisphosphonate alone without relapse.