summary Background: Familial mediterranean fever (FMF) is a single inherited autoinflammatory disease characterized by periodic fever with relatively short duration of 1 to 3 days and sterile serositis. Although the prevalence rate is highest in the Mediterranean coastal area, a large number of cases have been reported recently by genetic analysis by identification of MEFV (Mediterranean fever) which is responsible gene in Japan too. In outpatient department of rheumatology, diagnosis and treatment of FMF is performed in cases where fever and abdominal pain attack are repeated for a short period of time. Patients and Methods: We examined cases in which symptoms considered periodic seizures were repeated, excluding autoimmune diseases, infectious diseases, and malignant tumors. In both cases, genetic analysis is performed as auxiliary diagnosis. Results: Seven cases satisfied the Tel-Hashomer criteria criteria and MEFV gene mutation was detected. Everyone was a female, and half had seizure symptoms at menstruation. Even though there is a difference in the amount of colchicine to be used, either one is effective. Conclusion: In cases of periodic symptoms or cases called periodic fever, exclusion diagnosis is carried out, there is a need to suspect FMF, determine the effect of colchicine, and perform genetic analysis.

Familial Mediterranean fever (FMF) is a hereditary autoinflammatory disease caused by Mediterranean FeVergene (MEFV) mutations on Chromosome 16, and characterized by periodic fever of and serositis. FMF is the result of gain-of-function mutations in pyrin that lead to interleukin-1β activation. FMF can be classified as "typical" and "atypical" types based on clinical finding and genetic screening. Although MEFV genotyping has enabled FMF to be confirmed in some cases, the diagnosis remains predominantly clinical since genotyping has shown that the disease is characterized by variable manifestations in Japanese. In 1976, the first report performed on the case of Japanese FMF with periodic fever of and serositis. Since 2002, genetic analyses are performed on Japanese FMF patients by K. Shiozaki et al. and N. Tomiyama et al. In our case, she was a 25-year-old Japanese woman with at periodic fever and abdominal pain. MEFV gene analysis demonstrated a heterozygous mutation of variant M694I, leading to a diagnosis of FMF. After the increase dose (up to 3 mg/day) of colchicine, periodic fever and abdominal pain disappeared. It is the important candidate of FMF for differential diagnosis with unexplained periodic fever and serositis, such as our case.