Is age associated with disease severity and compliance to treatment in children with familial Mediterranean fever?

Familial Mediterranean Fever (FMF) is the most common monogenic autoinflammatory disease in the world. The disease characteristics may vary in different age groups. In this study, we aimed to compare disease characteristics and treatment compliance according to the age of pediatric FMF patients. This is a single-center, cross-sectional study. Between August and October 2016, patients who were diagnosed with FMF, participated to the study. 378 pediatric FMF patients were enrolled in the study. Among those, age at symptom onset was ≤ 5 years in 69%, 6-11 years in 26% and ≥ 12 years in 5%. Patients older than 12 years old at symptom onset, had significantly less frequent fever attacks than the patients from other age groups. Patients younger than 5 years old at symptom onset had significantly higher international severity scoring system for FMF (ISSF) than other patients. And M694V homozygosity was significantly more frequent in patients with younger age at symptom onset. Patients younger than 5 years old were using their drugs more regularly than the other age groups (p = 0.002). Drug compliance was 90.5% in patients ≤ 5 years, 64.4% in patients 6-11 years, 58.3% in patients ≥ 12 years. The disease characteristics of FMF may differ between patients with different age at symptom onset. Younger age at disease onset seems to be related with more severe course; thus these patients should be followed-up more closely. In addition, treatment compliance which is critical for prevention of amyloidosis in FMF should be questioned especially in adolescent patients.