Background/Purpose: Familial Mediterranean fever (FMF) is a rare hereditary autoinflammatory disease that predominantly affects, but is not limited to, persons of Middle Eastern ancestry. In Germany, roughly 10% of the general population has Mediterranean roots or migrated from the area of the Silk Road and may therefore be at risk of developing FMF. To our knowledge, epidemiologic data on FMF in Germany remain limited and no analyses of corresponding claims data have been published previously. The aim of this study was to explore the epidemiology of FMF in Germany and to describe demographic characteristics of the affected population.

Methods: We analyzed the database of the Institute for Applied Health Research Berlin (InGef). This database contains a representative subset of anonymized claims based on about 4 million members of the statutory health insurance (SHI) in Germany (overall about 73 million members). Individuals included in this analysis had to be continuously observable between 01-JAN-2012 and 31-DEC-2017. Prevalence and incidence were calculated for two years, 2014 and 2015. FMF patients were identified by ICD codes E85.0 (familial Mediterranean fever) and M14.4 (amyloid arthropathy).

Results: A total of 383 (11.99/100,000) prevalent FMF patients were identified, of whom 111 (28.98%) were < 18 years of age. Adults constituted 71.02% of prevalent cases. Females represented 48.65% of the pediatric population and 49.26% of the adult population. Also, 138 (4.23/100,000) incident cases were observed with a lower number of pediatric patients (47 or 34.06%) than adults (91 or 65.94%) and balanced proportions of males and females. Median age of incident patients was 30 years.

Associated rheumatic conditions diagnosed most frequently were juvenile arthritis, rheumatoid arthritis, and spondyloarthritis.

Conclusion: Our analysis provides a broad and current picture of FMF in Germany: We find a 2-year prevalence of about 0.012% for FMF across 2014 and 2015, corresponding to an extrapolated population of about 5,800 affected subjects among SHI members in Germany. The observed 2-year incidence of 0.004% in this population corresponds to approximately 2,100 newly diagnosed patients in 2014 and 2015 (i.e. about 1,050 per year). This high number of newly diagnosed patients in the adult population is unique and surprising, given the predominant onset and diagnosis of FMF during childhood reported in other publications. The cross-sectional design and lack of information on ethnic background constitute methodical limitations of this analysis. Future studies would be needed to assess, if awareness and early diagnosis of FMF improve over time.