Three patients with familial Mediterranean fever: a possible underdiagnosed entity in Japan

Area of Science:

• Genetics and Immunology
• Autoinflammatory Disorders
• Rare Disease Epidemiology

Background:

• Familial Mediterranean fever (FMF) is an autosomal recessive autoinflammatory disease.
• Characterized by recurrent episodes of fever and serosal inflammation.
• Predominantly reported in Mediterranean populations, considered rare in Japan.

Observation:

• Three unrelated FMF cases were treated within one year in a Japanese city of 144,000 residents.
• Two of these diagnosed patients were over 70 years old.
• This observation challenges the notion of FMF being exceedingly rare in Japan.

Findings:

• The incidence of FMF in this specific Japanese urban population suggests a higher prevalence than previously estimated.
• The diagnosis in elderly patients indicates potential for delayed or missed diagnoses in older demographics.
• This case series highlights the importance of considering FMF in individuals presenting with recurrent inflammatory symptoms, irrespective of geographic origin.

Implications:

• FMF may be significantly underdiagnosed in Japan and potentially other non-Mediterranean countries.
• Clinical awareness and diagnostic criteria for FMF should be re-evaluated for broader applicability.
• Further epidemiological studies are warranted to determine the true prevalence of FMF in Japan.