抄録
The differential diagnosis between polymyalgia rheumatica and elderly-onset rheumatoid arthritis is difficult because these diseases share similar clinical findings, especially at onset. We report a case of elderly-onset rheumatoid arthritis that was differentiate from polymyalgia rheumatica on the detection of synovitis of the acromioclavicular joint. A 73-year-old man was admitted to our hospital because of pain and bilateral stiffness in his shoulders and hips. Tests for rheumatoid factor and anti-cyclic citrullinated peptide antibody were negative. Bone erosions and joint space narrowing were not detected by radiographic examination of the glenohumeral and wrist joints, and polymyalgia rheumatica was suspected. Diagnostic treatment with prednisolone (15 mg per day) was started, but his arthralgia did not disappear. Further testing by radiography and magenetic resonance imaging (MRI) of the acromioclavicular joint showed synovitis and bone erosions. On the fourteenth day after initiation of steroid therapy, morning stiffness and arthralgia of the bilateral finger joints and wrist joints appeared, and synovitis and bone erosions of carpal bones were detected by MRI. Therefore, the diagnosis of elderly-onset rheumatoid arthritis was made. Acromioclavicular joint synovitis would be useful in the differential diagnosis between polymyalgia rheumatica and elderly-onset rheumatoid arthritis.
