Familial mediterranean fever in a patient with ankylosing spondylitis: could familial mediterranean fever explain a typical eight-year ankylosing spondylitis?

Patients with familial mediterranean fever (FMF) often present with musculoskeletal involvement typical of spondyloarthropathy (SpA) or ankylosing spondylitis (AS), posing a diagnostic challenge for medical practitioners and leading to the description of the FMF-related SpA/AS clinical spectrum. Currently, the available data focuses on SpA diagnosis in patients with known FMF, while the contrary is rarely reported in the medical literature. We describe an unusual case of concomitant FMF diagnosis in a patient with an eight-year long history of typical, human leukocyte antigen-B27 positive AS on adalimumab treatment, who presented with recurrent febrile attacks and abdominal pain. The laboratory work-up revealed high titres of serum amyloid A while genetic testing was positive for the pathogenic M694V heterozygous variant in the MEFV gene. The patient was promptly treated with colchicine, showing complete remission of clinical symptoms and normalisation of inflammatory markers to date. We also performed a review of the available literature elaborating on the interrelationship of AS and FMF in terms of pathogenesis and clinical characteristics. Our case highlights the need for reporting of similar cases and further explores the association of AS and FMF as distinct clinical entities or as constituents of the same disease continuum model.