Late-onset familial mediterranean fever: single-center experience and literature review

Familial Mediterranean fever (FMF) is a hereditary, autoinflammatory disease characterized by recurrent fever and serositis attacks. The disease onset occurs before 20 years of age in 90% of patients and rarely after the 4th decade. The aim of this study is to screen our FMF patient pool for patients with disease onset after age of 40 and to compare them to patients with early onset with regard to clinical and genetic features. The charts of 2020 patients registered in our FMF center in the years 2008–2017 were screened with regard to age of disease onset. Patients with disease onset after the age of 40 were considered as late-onset group (Group 1). The control group (Group 2) consisted of patients with a disease onset before the age of 20 who were randomly selected from the patient pool with twice the number of probands. Demographic, clinical and genetic data were recorded. Out of 2020 patients, the attacks of FMF had started after the fourth decade in 41 patients (2.02%), (Group 1). The male to female ratio was 1:1.7 in both groups. The delay of diagnosis was 5.6 ± 5.75 years in group 1, 10.7 ± 12.3 years in group 2. The only significant difference with regard to clinical features between two groups was the frequency of fever, which was present in 26 (63.4%) patients in group 1 and 67 (81.7%) in group 2 (p = 0.026). M694V mutation was more prevalent among early-onset group whereas exon 2 variants were more frequent in patients with late onset. The mean colchicine dose in the last 6 months was 1.38 ± 0.64 mg in group 1, and 1.61 ± 0.47 mg in group 2. FMF may start after 40 years of age in approximately 2% of the patients. Lower frequency of fever, lower daily colchicine dose and lower prevalence of exon 10 mutations point out that FMF patients with a disease onset after 40 years of age experience a milder disease compared to those with an onset before the second decade of life.