A 55-year-old male had been experiencing pain over the left shoulder to the anterior part of the chest since two days. Physical examination indicated a body temperature of 37.8°C, as well as swelling, elevated temperature, and tenderness on the left side of the sternum (Figure 1). The pain worsened with elevation of the left shoulder, right rotation and retroflexion of the neck, and deep inspiration. Blood tests showed an inflammatory response (C-reactive protein, 13.1 mg/dL, erythrocyte sedimentation rate, 48 mm/h). Rheumatoid factor and anti-cyclic citrullinated peptide (anti-CCP) antibody were negative. Joint aspiration was not performed because ultrasonography did not detect the effusion of sternoclavicular joints. Computed tomography (CT) scan of the sternoclavicular joints revealed an erosive change in the left sternoclavicular joint. Magnetic resonance with the short-T1 inversion-recovery (MR-STIR) sequence showed an abnormal signal in the left sternoclavicular joint (Figure 2). A non-steroidal anti-inflammatory drug was orally administered, and the symptoms disappeared after one month. Although no skin eruption developed during the follow-up, sternoclavicular joint arthritis due to SAPHO syndrome was diagnosed.

Conditions of the sternoclavicular joints are sometimes misdiagnosed as shoulder diseases because sternoclavicular joints are involved during shoulder joint elevation. When inflammation related to sternoclavicular joint arthritis spreads to the sternocleidomastoid muscles, retroflexion of the neck or rotation to the unaffected side causes pain. Sternoclavicular joint arthritis may be caused by septic arthritis, osteoarthritis, rheumatoid arthritis, SAPHO syndrome, ankylosing spondylitis, psoriasis, gout, or pseudogout [1]. Among those, erosive changes of in sternoclavicular joints have been observed in rheumatoid arthritis, ankylosing spondylitis, psoriasis and SAPHO syndrome. Anti-CCP antibody was negative in this patient, making rheumatoid arthritis unlikely. Ankylosing spondylitis typically develops in young adults and occurs insidiously. Nail lesions and dactylitis were not observed, making psoriatic arthritis unlikely. Among patients with SAPHO syndrome, 65–90% experience damage in the bones and joints of the anterior chest. Skin symptoms such as severe acne and palmoplantar pustulosis aid the diagnosis of SAPHO syndrome. However, 32–60% of patients develop bone and joint symptoms several years before skin symptoms, and 15% of patients do not develop skin symptoms [2]. Osteolytic changes are often noted at an earlier stage with or without osteosclerotic findings [2]. A computed tomography scan reveals an erosive change in the bone, and MR-STIR imaging shows an abnormally high signal in the bone. MR-STIR imaging can help differentiate active lesions from chronic ones [3].

Magnetic resonance imaging scan is useful in the diagnosis of sternoclavicular joint arthritis and especially magnetic resonance with the short-T1 inversion-recovery imaging can help differentiate active sternoclavicular joint arthritis from chronic one.

1. Guglielmi G, Scalzo G, Cascavilla A, Salaffi F, Grassi W. Imaging of the seronegative anterior chest wall (ACW) syndromes. Clin Rheumatol 2008;27(7):815–21.   [CrossRef]   [Pubmed]    
2. Nguyen MT, Borchers A, Selmi C, Naguwa SM, Cheema G, Gershwin ME. The SAPHO syndrome. Semin Arthritis Rheum 2012;42(3):254–65.   [CrossRef]   [Pubmed]    
3. Earwaker JW, Cotten A. SAPHO: Syndrome or concept? Imaging findings. Skeletal Radiol 2003;32(6):311–27.   [CrossRef]   [Pubmed]