Sacroiliitis in familial Mediterranean fever: A rare joint involvement of the disease

AIM: Familial Mediterranean fever (FMF) is a monogenic autoinflammatory disease characterised by recurrent episodes of fever and polyserositis. Sacroiliac joint involvement is rare in FMF patients. The purpose of this study was to evaluate the demographic, clinical, laboratory and imaging findings of patients with FMF who developed sacroiliitis. METHODS: The files of paediatric patients aged 0-18 years who were followed up with a diagnosis of FMF were retrospectively reviewed. FMF patients with evidence of sacroiliitis on magnetic resonance imaging (MRI) were included in the study. RESULTS: Among 1062 FMF patients, 22 (12 males; median age 8.5) (2.1%) of them were found to have sacroiliitis. FMF was diagnosed before sacroiliitis in nine (40.9%) patients and after in 13 (59.1%) patients. The most common symptom in patients with sacroiliitis was low back pain (n = 21, 95.5%). In MEFV gene analysis, M694V was found in 16 (72.7%) patients and was the most common mutation. MRI showed evidence of sacroiliitis in all patients. All patients were using colchicine. Patients with FMF-associated sacroiliitis, remission was achieved with non-steroidal anti-inflammatory drugs in 12 (54.5%), conventional disease-modifying antirheumatic drugs in six (27.3%) and tumour necrosis factor inhibitor treatment in four (31.8%). Four (31.8%) patients experienced sacroiliitis when colchicine incompatible and four (31.8%) patients experienced sacroiliitis while using biologic agents for colchicine-resistant FMF. CONCLUSIONS: FMF-associated sacroiliitis should be considered especially in patients with M694V mutation if they have symptoms such as low back pain. Colchicine-resistant FMF patients should be evaluated for sacroiliitis symptoms at each visit.