SAPHO Syndrome

SAPHO syndrome (synovitis, acne, pustulosis, hyperostosis, osteitis) is a chronic inflammatory disorder of the skin and osteoarticular system, with sterile bone inflammation.

• Prevalence about 1 in 10,000; onset 30 to 50 years; women more than men.

• Part of the spectrum with chronic recurrent multifocal osteomyelitis (children).

• Immune dysregulation with IL-1, TNF, IL-17 and IL-23; Cutibacterium acnes proposed trigger.

• Anterior chest wall (sternoclavicular, manubriosternal, costoclavicular) is involved in 70 to 90%, plus spine and sacroiliac joints.

• Associations: palmoplantar pustulosis, severe acne (acne conglobata, fulminans), hidradenitis, pyoderma gangrenosum, IBD, psoriasis.

• Pain and swelling of the anterior chest wall (sternoclavicular hyperostosis), spine pain, sacroiliitis, peripheral arthritis, mandibular lesions.

• Palmoplantar pustulosis or severe acne (may precede, follow, or be absent).

• Fatigue, mild fever; relapsing remitting course.

• Complications: vertebral collapse, nerve compression, venous thrombosis (subclavian), joint ankylosis.

• Clinical criteria (Kahn): osteoarticular involvement with palmoplantar pustulosis or severe acne, or hyperostosis with or without dermatosis, or chronic recurrent multifocal osteomyelitis.

• Bone scintigraphy: "bull's head" sign at sternoclavicular region; whole body MRI shows bone marrow oedema.

• CT/radiographs: hyperostosis, osteitis, sclerosis.

• CRP, ESR may be normal or mildly raised; HLA-B27 usually negative; rheumatoid factor negative.

• Biopsy and cultures to exclude infectious osteomyelitis, tumour (sterile inflammation); exclude spondyloarthritis, SAPHO mimics.

• NSAIDs first line (naproxen 500 mg twice daily, indomethacin 25 to 50 mg three times daily).

• Bisphosphonates: pamidronate 60 mg IV monthly for 3 to 6 months or zoledronic acid 4 to 5 mg for resistant bone pain and oedema; remission in many.

• Conventional DMARDs: methotrexate 15 to 25 mg weekly, sulfasalazine 2 to 3 g daily, azathioprine.

• Biologics for refractory disease: TNF inhibitors (adalimumab 40 mg every 2 weeks, infliximab 5 mg/kg), IL-17 inhibitors (secukinumab 300 mg monthly), ustekinumab, IL-1 antagonists (anakinra 100 mg daily); JAK inhibitors (tofacitinib 5 mg twice daily).

• Antibiotic trials (azithromycin 500 mg three times weekly, doxycycline 100 mg twice daily) have anecdotal benefit, especially for acne.

• Skin: topical corticosteroids, retinoids, phototherapy, acitretin for pustulosis.

• Orthopaedic management of fractures or deformity; follow up on pain and imaging.