Background Familial Mediterranean Fever (FMF) is characterised with recurrent inflammatory attacks with serosal inflammation. The clinical findings of FMF is seen in a large spectrum. Tel Hashomer criteria are widely used for classifying FMF. According this criteria set FMF is classified as ‘definite’ and ‘probable’ disease. Objectives We aimed in this study to investigate the frequency of exon-10 MEFV mutations in ‘probable’ FMF patients according to Tel Hashomer criteria. Methods The study group consisted of 117 patients (79 male, 38 female, median age:31±11,12–69 which is classified as ‘probable’ FMF according to Tel-Hashomer criteria. The 12 frequently seen mutations in Turkey analysed in all blood samples and comparised with the previous reported ‘definite’ FMF data from Turkey. Results We found in probable FMF group single mutation in 36 patients (%30,8), two mutations in 56 patients (%47,9), 3 mutations in 5 patients (%4,3) and no mutations in 20 patients (%17,1). The distrubition of exon 10 mutations showed single exon-10 mutation in 46 patients (%39,3) and two exon-10 mutations only in 23 patients (%19,7). The detailed distrubition of MEFV mutations in ‘probable’ FMF group is shown in table 1. Conclusions We found decreased frequency of exon 10 mutations in the MEFV gene in “probable FMF’ group according to Tel-Hashomer criteria in comparison previous reported MEFV mutations data. The distribution of non-exon 10 mutations were similar in the definite FMF group. It is needed more clinical studies with large patient group for the clinical significance of non-exon 10 mutations in “probable” FMF patients. Reference [1] Cosan F, Ustek D, Oku B, Duymaz-Tozkir J, Cakiris A, Abaci N, Ocal L, Aral O, Gul A. Association of familial Mediterranean fever-related MEFV variations with ankylosing spondylitis. Arthritis Rheum2010Nov;62(11):3232–6. doi:10.1002/art.27683 Disclosure of Interest None declared