Frequency of rheumatic diseases in patients with familial Mediterranean fever

Purpose: Mutations in the Mediterranean FeVer (MEFV) gene, which causes familial Mediterranean fever (FMF), may also cause the emergence of other specific rheumatic diseases. This study aims to determine the frequency of other rheumatologic diseases in paediatric FMF patients, evaluate whether there are clinical and genetic differences between those with and without concomitant rheumatologic diseases, and compare the data with previous studies. 
Materials and methods: The files of FMF patients who were followed up at the paediatric rheumatology department were reviewed retrospectively. Demographic data, MEFV mutations, treatment, disease severity scores, and concomitant rheumatic diseases were recorded from the files. 
Results: There were 303 FMF patients (154 female/149 male). The mean age at diagnosis was 7.04±3.9 years. The mean disease duration was 5.33±3.13 years. In the cohort, 41 FMF patients (13.5%) were diagnosed with another rheumatic disease. There were 22 cases of juvenile idiopathic arthritis (53.6%), seven cases of vasculitis (17%), six cases of periodic fever aphthous stomatitis and adenitis syndrome (14.6%), three cases of Behçet disease (7.3%), two cases of acute rheumatic fever (4.8%), and one case of systemic lupus erythematosus (2.4%). 32 of these 41 FMF patients (78%) had the M694V mutation (homozygous in 11, heterozygous in 21). Disease activity scores PRAS and ISSF scores were higher in FMF with rheumatic diseases (p=0.002 and p