Disease severity in children and adolescents with familial Mediterranean fever: a comparative study to explore environmental effects on a monogenic disease

Background: Worldwide, familial Mediterranean fever (FMF) is the most common autoinflammatory disease. It has been suggested that environmental factors affect the phenotype as some patients do not develop the complication of secondary amyloidosis. Objective: To analyse whether disease severity in Turkish children with FMF, living in Turkey and Germany is different. Patients and methods: A total of 55 Turkish children living in Turkey were compared with 45 Turkish children born and raised in Germany. Mean age among the group from Turkey and Germany was 42.2 and 44.29 months, respectively. M694V was the leading mutation in both groups. The severity scores were compared with two scoring systems, modified according to published paediatric data for dosage. Results: There was no significant difference between the mean C-reactive protein and erythrocyte sedimentation rate levels of the two groups. According to the modified Sheba Center score, 78.2% of patients from the group living in Turkey had a severe course compared with 34.1% from the group living in Germany. The modified score of Pras et al also showed more severe disease in the patients from Turkey. The difference between the two groups for both scoring systems were significant (both p < 0.05). Conclusions: We believe the modified scores that we introduce can be widely used for children. Our results suggest that the environment affects the phenotype of a monogenic disease of the innate inflammatory pathway.