Gas-containing iliopsoas bursitis in the setting of degenerative osteoarthritis

A case of rheumatoid arthritis with bilateral shoulder bursitis accompanied by gas image

We experienced a case of bilateral shoulder bursitis with gas images in a rheumatoid arthritis (RA) patient. A 60-year-old man with RA had been treated with weekly methotrexate 10 mg and daily prednisolone (PSL) 10 mg for 7 months. Generalized pain, especially in the bilateral shoulder joints, developed and exacerbated daily with increased C-reactive protein (CRP) level. Despite the initiation of biweekly sarilumab 200 mg, joint symptoms and CRP level continued to worsen. Computed tomography (CT) scan to determine the cause of severe shoulder inflammation revealed low absorption areas with contrast effects at the margins around the bilateral shoulder joints, accompanied by internal gas images. In addition, magnetic resonance imaging demonstrated subacromial bursae and coracoid bursae and bursitis, leading to the suspicion of abscess formation depending on the presence of gas image. In spite of antimicrobial therapy, arthralgia did not improve, and a CT-guided arthrocentesis of the left shoulder joint resulted in negative findings of infection in culture and pathological examinations. Switching treatment to intensive anti-inflammatory therapy with high-dose steroids and etanercept finally improved symptoms and CRP levels associated with the reduction of low absorption areas and disappearance of gas images at bilateral shoulder joints. Our case indicated that bursitis with gas image in RA patients involves unusual pathophysiology and requires intensive anti-rheumatic treatment.