Background & objectives: FMF is an auto-inflammatory and hereditary periodic disorder. The symptoms can occur in more than 80% during the first decade of life. With regard to high prevalence of FMF in northwest of Iran, this study was conducted to introduce especial features of FMF in this area.

Methods: This is a descriptive study performed on 403 patients with diagnosis of FMF according to the Tel-Hashomer criteria. Information obtained from patients' file and entered in the questionnaire. Data analyzed by SPSS v20 using simple descriptive statistical analysis.

Results: In this study 228 (56.6%) patients were male, and the mean age of patients was 21.03 years. The common symptoms were abdominal pain in 93.3% and fever in 88.1% of patients. Abdominal pain was the main complaint(49.6%), the average duration of pain was 43.3±34.5 hours and the average attack-free period was 36.5±29.6 days. 15.1% of patients had positive family history and 12.7% had history of appendectomy. Delayed diagnosis was more than three years in 52.3% of patients. Genetic analysis has been done in 239 patients in which 21.33% had no mutations, 39.7% were compound heterozygous genotype, 25.52% heterozygote and 13.38% had compound homozygous mutations. The most common mutations were M694V/V726A (10.46%) and the most common alleles were M694V (20.9%) and V726A (12.7%). The M694V-V726A genotype (12.7%) was the most common combined mutations in male and the common mutations in female was M694V/M694V (10.4%). Among the patients with abdominal pain M694V/V726A (12.5%) was more common. The genotypes of M680I/V726A (13.9%), M694/V726A and M694V/R761H (16.7%) and the M694V/M694V (33.3%) had the common mutations in patients with fever, chest pain and joint symptoms respectively.

Conclusion: First decade is usual age to presentation of FMF. M694V is the most common mutation and M694V-V726A is the common compound heterozygous mutation. MEFV mutations in this study are similar to Arabs results. It seems that clinical criteria still are the best way in diagnosis of FMF in spite of the fact that erysipelas like skin rash  is not common as a clinical criteria in this area