Atypical Familial Mediterranean Fever Presenting with Recurrent Migratory Polyarthritis.

A 38-year-old Japanese man without any significant past medical history was referred to our clinic to undergo further examination for a "refractory infection in his joints". He suffered recurrent migratory polyarthritis starting from bilateral knees to his right elbow. Certain antibiotic therapies appeared to improve his symptoms, but the symptoms recurred due to the migratory nature of arthritis. A diagnosis of familial Mediterranean fever (FMF) was considered and diagnostic tests were performed. Not many differential diagnoses exist for migratory polyarthritis, particularly when it has a recurrent nature. The administration of antibiotics without sufficient diagnostic consideration can cause a delay in making an accurate diagnosis and thereby also cause a delay in administering appropriate treatment.