Polyarteritis nodosa in patients with Familial Mediterranean Fever (FMF): A concomitant disease or a feature of FMF?

Background: Familial Mediterranean Fever (FMF) is caused by mutations in the gene encoding pyrin and is characterized by self-limited, recurrent attacks of fever and serositis. Vasculitis has been increasingly reported in FMF. A study evaluating the prognosis in FMF and polyarteritis nodosa (PAN) patients has not been reported previously. Objectives: To determine the special characteristics and the prognosis of PAN in FMF patients. Methods: A questionnaire was used for the present survey. The setting was 7 referral centers from Turkey and Israel. Seventeen patients who were diagnosed with FMF and who developed PAN were included. PAN was diagnosed in those who met the Chapel Hill consensus criteria for microscopic polyarteritis or classic PAN. The clinical features of these 17 patients and the outcomes of their vasculitis were analyzed. Results: The age at diagnosis of PAN in these FMF patients ranged from 3.5 to 37 years. All patients had constitutional symptoms, elevated acute phase reactants, and myalgia at the time PAN was diagnosed. The diagnosis of PAN was confirmed by renal angiography in 8 patients, by renal biopsy in 6 patients, and by muscle and/or nodule biopsies in 6 patients. A number of patients had definite features of both classic PAN and microscopic polyarteritis. Conclusions: When compared with other PAN patients, those with FMF tended to have a younger age at PAN onset, more frequent perirenal hematomas, and an overall better prognosis. The cases with overlapping features of microscopic and classic PAN pose a problem for the current classification of vasculitis. We suggest that the clinical representation of PAN in FMF patients has certain characteristics and may be a feature of FMF per se. Semin Arthritis Rheum 30:281-287. Copyright © 2001 by W.B. Saunders Company