Long-term clinical course of two rare cases of synovitis-acne-pustulosis-hyperostosis-osteomyelitis syndrome involving only unilateral femur.

Synovitis-acne-pustulosis-hyperostosis-osteomyelitis (SAPHO) syndrome is characterised by aseptic osteitis and is often complicated by pustular dermatitis, such as palmoplantar pustulosis or acne. Although bone lesions are most found in the anterior thoracic region or spine, femoral lesions are not well documented in the literature. There is no established treatment for this condition, and few reports have described its long-term course. Here, we describe two cases of SAPHO syndrome involving the femur and discuss their long-term follow-up. A 40-year-old man (Case 1) presented with right thigh pain. Fifteen years after the initial diagnosis, the pain could be controlled with minomycin, salazosulfapyridine, and methotrexate. X-rays of the femur showed gradual cortical thickening. Although there were waves of pain, it gradually improved with the adjustment of drugs 25 years following the initial diagnosis. A 35-year-old man (Case 2) with right thigh pain was prescribed salazosulfapyridine and methotrexate; however, these were ineffective. Alendronate and guselkumab also proved ineffective. Ultimately, infliximab was started 9 years following disease onset, and pain became manageable. X-rays of the femur showed cortical thickening. SAPHO syndrome can be managed with drug therapies, such as nonsteroidal anti-inflammatory drugs, methotrexate, and conventional synthetic disease-modifying antirheumatic drugs; however, there are occasional treatment-resistant cases.