Abstract
Anti-nRNP antibody, which was first reported as a serological marker of mixed connective tissue disease, has also been known to be detected in various other diseases such as Raynaud’s phenomenon, systemic sclerosis, systimic lupus erythematosus, and polymyositis. We herein report two cases of mixed connective tissue disease that were initially diagnosed as rheumatoid arthritis (RA). The first patient, a 70-year-old woman, was initially diagnosed as RA because of arthralgia and a positive rheumatoid factor. One year later, she consulted us for contact dermatitis and still had arthralgia. Antinuclear antibody tests revealed the presence of anti-nRNP antibodies. She had slightly swollen fingers and her chest X-ray showed mild pulmonary fibrosis. She was treated with prednisolone (10mg/day), resulting in an improvement in the arthralgia. The second patient, a 27-year-old woman, was also initially diagnosed as RA because of arthralgia and a positive rheumatoid factor. One year later, she presented with Raynaud’s phenomenon and swollen fingers. Antinuclear antibody tests demonstrated the presence of anti-nRNP antibody. Neither patient fulfilled the criteria for RA as proposed by the American Rheumatism Association. A total of 52 patients with anti-nRNP antibodies were examined to reveal first manifestations. Arthralgia was observed in 10/52(19.2%). In addition, rheumatoid factor was reported to often be detected in patients with anti-nRNP antibodies. Therefore, it appears that patients with anti-nRNP antibodies may initially be misdiagnosed as RA when they have arthralgia as a first manifestation and a positive rheumatoid factor.
