SAPHO (synovitis, acne, pustulosis, hyperostosis, and osteitis) syndrome

• is a rare disorder characterized by cutaneous and osteoarticular manifestations that include acne, palmoplantar pustulosis, psoriasis, arthralgia, chest pain, and enthesitis
  • skin manifestations may be evident at the time of presentation with osteoarticular symptoms, but may have occurred years earlier or may develop later
    
    
  • laboratory evaluation is nonspecific, and magnetic resonance imaging is the modality of choice for evaluating osteoarticular manifestations
    
    
  • bone biopsies are performed to rule out malignancy and infection and primarily exhibit a sterile neutrophilic inflammatory infiltrate early in the disease; late-stage findings include enlarged sclerotic trabeculae with increased osteocytes and marrow fibrosis
    
    
• generally considered to be a rare condition, possibly due to being underdiagnosed - a prevalence estimate of <1/10,000 is frequently mentioned
  
  
• SAPHO syndrome may present at any age but is most commonly seen in children and young to middle-aged adults - there may be a female preponderance
  
  
• bony involvement is most notable at the sternoclavicular joint
  • anterior chest wall is affected in 63% to 73% of patients with SAPHO syndrome
    • in early disease, radiography is often normal
    • early lesions, when present, are osteolytic and may be accompanied by endosteal or periosteal reaction. As the disease progresses, the lesions become sclerotic
    • pathognomonic bull's head sign can be seen with whole-body scintigraphy and refers to increased radiotracer uptake in the sternoclavicular joints and sternum-the manubrium represents the skull of the bull, and the sternoclavicular joints are the horns (1)
      • unlike plain radiography, whole-body scintigraphy and whole-body magnetic resonance imaging may identify subclinical disease, although magnetic resonance imaging is preferred because it has similar sensitivity without the radiation exposure
      • bone biopsy is also necessary to rule out malignancy and osteomyelitis (1)

Reference:

1. Nguyen M.T., Borchers A., Selmi C., Naguwa S.M., Cheema G., Gershwin M.E. The SAPHO syndrome. Semin Arthritis Rheum. 2012;42(3):254-265