Not easy-peasy to diagnose: familial Mediterranean fever unaccompanied by fever

Classical attacks of familial Mediterranean fever (FMF) are often accompanied by fever, but some of the patients have attacks without fever. This study aimed to compare the characteristics of FMF patients with and without fever during their attacks and draw attention to the different clinical presentations of FMF in children. Medical files of patients aged 0-18 years who were followed up with the diagnosis of FMF in two reference pediatric rheumatology centers were reviewed retrospectively. The patients were divided into two groups: children who had had no fever in any of their attacks were assigned as group 1, and those who had fever during their attacks were classified as group 2. Out of 2003 patients evaluated, 191 (9.53%) patients had attacks not accompanied by fever and their median age at onset of symptoms (7.0 vs. 4.0 years, p < 0.001) and the median age at diagnosis (8.6 vs. 6.0 years, p < 0.001) were significantly higher; however, group 2 had a delay in diagnosis. The annual number of attacks and abdominal attacks were more common in group 2; arthritis, arthralgia, erysipelas-like rash, exercise-induced leg pain, and myalgia were more common in group 1.    Conclusion: The data from the assessment of children with FMF attacks not accompanied with fever were presented for the first time. Children with late age onset of FMF and dominance of musculoskeletal features may display attacks not accompanied with fever. What is Known: • Familial Mediterranean fever (FMF) is the most common inherited auto-inflammatory disease, characterized by recurrent attacks of fever, serositis, and musculoskeletal symptoms. • Although fever is the most common symptom, few studies have reported attacks without fever. What is New: • The aim of this study was to identify patients with FMF but without fever during attacks and to demonstrate their distinctive presentations. • We found that 7% of our patients had afebrile attacks with predominant musculoskeletal symptoms and were diagnosed earlier than patients with febrile attacks, probably due to early referral to pediatric rheumatology clinics.