Five cases of seronegative persistent inflammatory monoarthritis improved with biological therapy.

Persistent inflammatory monoarthritis is defined as inflammation of one joint that continues for longer than 3 months. Most cases remain as nonspecific arthritis after several years. Persistent inflammatory monoarthritis is difficult to diagnose and treat in the early stage because there are no criteria for diagnosis and treatment. We report five seronegative persistent inflammatory monoarthritis cases that affected the left knee, right knee, left knee, left ankle, and right knee. All patients underwent joint punctures; two patients received steroid injections in the affected joint. The bacterial and mycobacterial culture were negative in all patients. Two patients received oral steroids, and two patients were administered nonsteroidal anti-inflammatory drugs; however, their symptoms did not improve, and one patient experienced progression of joint destruction. We investigated the usefulness of biological disease-modifying antirheumatic drugs for the treatment of seronegative persistent inflammatory monoarthritis. We obtained a remarkable improvement effect and prevented the advance of joint destruction.