SUMMARY Objective: The aim of this study is to assess presence of MEFV (MEditerranean FeVer) gene mutations and relationship between those mutations and disease activity in ankylosing spondylitis (AS). Method: Study group was consisted of 34 patients with AS, and 35 healthy volunteers enrolled to study as control group. 12 MEFV gene mutations were screened by Stripe-Assay technique. Patients with AS were divided into 2 subgroups according to whether they are MEFV gene positive or negative. Demographic data of study group were questioned. Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), Bath Ankylosing Spondylitis Functional Index (BASFI) and The Bath Ankylosing Spondylitis Metrology Index (BASMI), peripheral joint involvement, and drug use were used as clinical parameters; Visual Analog Scale (VAS) was used to assess pain, and erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) were assessed as laboratory parameters. Results: Among 34 patients with AS, it was found that 5 patients (35.7%) were positive for E148Q, 2 patients (14.2%) for M694V, 2 patients (14.2%) for A744S, 2 patients (14.2%) for V726A and 1 patient (7.1%) for each of the M680I, R761H, P369S. Among 35 individuals in control group, E148Q was detected in two (5.7%) and M694V was detected in another two (5.7%). When MEFV gene mutations were compared between study group and control group, there was no significant difference (p>0.05). There was significant difference between MEFV carriers and non-carriers regarding BASDAI, CRP and ESR values and positive family history whereas no difference was found in BASMI, BASFI, VAS, disease duration and biological agent use. Conclusions: It was thought that MEFV mutation frequency in AS patients was similar with control group but disease should have more progressive course in MEFV positive AS patients. To address this issue, further studies with large series are needed. Keywords: Anklyosing spondylitis, MEFV gene mutations, disease activity OZET Amac: Ankilozan Spondilit (AS) hastalarinda MEFV (MEditerranean FeVer) gen mutasyonlarinin varligini ve bunun hastalik aktivitesi ile olan iliskisini degerlendirmektir. Yontem: AS tanisi olan 34 hasta ve 35 saglikli gonullulerden olusan kontrol gurubu alindi. Strip-assay teknigi ile 12 adet MEFV gen mutasyonuna bakildi. AS hastalari MEFV mutasyonu pozitif ve negatif olarak iki gruba ayrildi. Her iki grubun demografik verileri sorgulandi. Klinik parametre olarak, Bath Ankilozan Spondilit Hastalik Aktivite Indeksi (BASDAI), Bath Ankilozan Spondilit Fonksiyonel Indeksi (BASFI), Bath Ankilozan Spondilit Metroloji Indeksi (BASMI), agri icin Vizuel Analog Skala (VAS), periferik eklem tutulumu, ilac kullanimi, labaratuvar olarak eritrosit sedimantayon hizi (ESH) ve C-Reaktif Protein (CRP) degerlendirildi. Bulgular: AS’li 34 hastanin 7’sinde (%20,6) E148Q, 4’unde (%11,8) M694V, 2’sinde (%5,9) A744S, 2’sinde (%5,9) V726A, 1’er hastada da (%2,9) M6801, R761H, P369S pozitif olarak bulundu. Kontrol grubundaki 35 bireyden 2’sinde (%5,7) E148Q, 2’sinde (%5,7) M694V tespit edildi. Hasta ve kontrol grubundaki MEFV mutasyonlari karsilastirildiginda farklilik onemsizdi (p>0,05). MEFV mutasyonu pozitif olan 14 AS’li hastanin 7’sinde (%50,0) E148Q, 4’unde (%28,6) M694V tespit edilmis olup bu oran istatiksel olarak anlamli bulundu (p<0,05). MEFV mutasyonu tasiyan ve tasimayanlar arasinda BASDAI, CRP, ESH ve pozitif aile oykusu anlamli bulunurken, BASMI, BASFI, VAS, hastalik suresi, biyolojik ajan kullanimi acisindan fark bulunamamistir. Sonuc: AS hastalarinda MEFV mutasyon sikliginin kontrol grubu ile benzer oldugu fakat MEFV mutasyonu pozitif olan AS hastalarinda hastaligin daha progresif seyredebilecegi dusunulmektedir. Bununla ilgili daha cok olguyla yapilacak calismalara ihtiyac vardir. Anahtar sozcukler: Ankilozan spondilit, MEFV gen mutasyonlari, hastalik aktivitesi