The expanded spectrum of arthritis in children with familial Mediterranean fever.

Introduction: Familial Mediterranean fever (FMF) is the most common monogenic autoinflammatory disease that can present with various forms of arthritis. This retrospective study aims to evaluate the characteristics of patients with arthritis in a large pediatric cohort of FMF patients.
Methods: The demographic and clinical data were extracted from electronic medical records. Patients with arthritis were grouped as arthritis of FMF and arthritis of FMF-associated diseases.
Results: A total of 541 patients were followed with a diagnosis of FMF in the last 5 years. Acute arthritis of FMF (n: 138) was the most common cause. It showed a recurrent course in the majority with a longer duration than other attack symptoms. Significantly higher frequencies of biallelic exon 10 and M694V mutations, erysipelas-like erythema, and protracted febrile myalgia were detected in these patients, particularly in those older than 2 years of age. Sacroiliitis of FMF was the second most common cause (n: 19). Patients with acute arthritis and sacroiliitis of FMF needed higher doses of colchicine. One patient with neonatal-onset FMF and M694V homozygosity was diagnosed with protracted arthritis. Arthritides of FMF-associated diseases including IgA vasculitis (n: 10), juvenile idiopathic arthritis (n: 9), chronic nonbacterial osteomyelitis (n: 5), and inflammatory bowel disease (n: 2) were detected in 26 patients.
Conclusions: Arthritis is an important clinical finding of FMF mostly associated with M694V mutations. The frequency of protracted arthritis is declined, whereas sacroiliitis of FMF and arthritis of associated diseases expand the spectrum of arthritis. This study represents the changing face and current perspectives of arthritis in FMF. Key Points • Arthritis is an important clinical finding of familial Mediterranean fever (FMF) that can present in various forms • Arthritis is most likely associated with M694V mutations • The frequency of protracted arthritis is declined whereas sacroiliitis of FMF and arthritis of associated diseases expand the spectrum of arthritis in FMF.
(© 2022. International League of Associations for Rheumatology (ILAR).)