The Possible Relationship Between Familial Mediterranean Fever and Chronic Nonbacterial Osteomyelitis: Coincidence or Coexistence?

BACKGROUND/OBJECTIVES: Chronic nonbacterial osteomyelitis (CNO) is an inflammatory disease characterized by recurrent attacks and remissions due to sterile bone inflammation. The CNO may be accompanied by various inflammatory diseases. The aims of our study were to determine the clinical, laboratory, and radiological characteristics of children with CNO, and to investigate the possible effect of concomitant diseases on the course of CNO. METHODS: Twenty-three patients who were diagnosed with CNO between 2012 and 2019 were analyzed. Demographic characteristics, clinical courses, laboratory and imaging findings, and concomitant diseases were recorded. The characteristics of the CNO patients with and without concomitant diseases were compared. RESULTS: The mean ± SD age of patients at the time of diagnosis and the last follow-up was 10.46 ± 4.1 and 12.47 ± 4.47 years, respectively. The median (range) time interval between disease onset and diagnosis was 5.33 (1-55) months. The mean ± SD duration of disease was 24.71 ± 16.76 months. Twelve patients (52.2%) were male. The most commonly affected areas were femur (74%), tibia/fibula (74%), and pelvis (52.2%). Age at symptom onset, age at diagnosis, mean number of lesions, presence of sacroiliitis, acute phase reactants at the start of disease, clinical and radiological remission rates, and treatment responses were not significantly different between the 13 patients with concomitant diseases and those without. Eight patients (34.8%) had familial Mediterranean fever (FMF), and all of them had exon 10 mutations. Four patients (17.4%) had juvenile spondylarthritis, one had inflammatory bowel disease, and one had psoriatic arthritis as concomitant diseases. Clinical remission was achieved in 19 patients (82.6%) and complete remission in 11 patients (47.8%) at the time of follow-up. CONCLUSIONS: In our cohort, half of the patients with CNO had concomitant diseases, with FMF being the most common. We think that the coexistence of FMF and CNO is not a coincidental one and that both may result due to an abnormality of a common pathogenetic pathway.