Arthritis as the sole episodic manifestation of familial Mediterranean fever

Objective. To clinically and genetically characterize patients with familial Mediterranean fever (FMF) in whom arthritis constitutes the only manifestation, and to establish the most important features distinguishing FMF arthritis in such a setting from other forms of mono/oligo arthritides. Methods. The study population comprised 14 patients with episodes of arthritis as the only manifestation of FMF who nevertheless fulfilled the diagnostic criteria for FMF. The control group consisted of 28 patients with episodic mono/oligo arthritis of different disease entities (palindromic, reactive, inflammatory bowel disease, Reiter's, seronegative spondyloarthropathy, chronic juvenile, Behçet's, and gouty arthritis) who presented to the rheumatology clinic during the study period. Patients in both groups underwent clinical evaluation and donated blood for FMF gene analysis. Results. The study and control groups shared similar age and sex distribution and experienced the monoarthritic attacks at similar sites, usually the knee and ankle joint. The 2 groups differed significantly in features of arthritis (which were febrile and of short duration in FMF), family history of FMF, mutation analysis, and response to colchicine. These differences allowed the defining of a rule, which readily distinguishes FMF arthritis from other forms of episodic mono/oligo arthritis. Conclusion. The clinical, ethnic, and genetic features of recurrent monoarthritis of FMF are specific and may separate FMF from other entities with mono/oligo arthritis.