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Polyautoimmunity: axSpA and Familial Mediterranean Fever

Rachel Tate, DO

Mysteries behind polyautoimmunity have confounded rheumatologists for decades. One such association, the co-existence of Familial Mediterranean Fever (FMF) and axial spondyloarthritis (axSpA), remains rare. In fact, we believe the rate to be between 0.5% and 7.5%. Two abstracts looking at axSpA and FMF were highlighted during ACR Convergence 2021. 

Abstract 0378 reviewed the demographics and disease features of axSpA patients with and without FMF.  A total of 9630 FMF patients were identified using ICD 10 coding (E85.0) from the Hacettepe University Hospital database in Turkey. Of these, 241 were also found to have axSpA (M45) coding as well as sacroiliitis on imaging (XR and/or MRI.) FMF diagnosis was confirmed by the Tel-Hashomer criteria. 

136 patients were confirmed to have both FMF+axSpA, of these patients 107 were previously treated with biologics. These patients were matched to 102 axSpA only controls who had also been treated with biologics. Researchers found that while signs and symptoms of axSpA were comparable, those with concurrent FMF were are higher risk for amyloidosis (7.5% vs 1%) and lumbar mSASSS scores and lumbar syndesmophyte frequencies were higher in the axSpA+FMF group. Interestingly, they also determined that the presence of hip OA and total hip replacement was also more prevalent in those with FMF+axSpA. 

Abstract 1108 looked further into the FMF+SpA patients to better assess demographics and other baseline characteristics of the FMF+SpA patients that may lead to better understanding hip OA and need for total joint replacement in these patients. 

The study reviewed charts from 111 Turkish patients who met the same criteria for FMF+SpA as above for diagnoses. 53.2% of these patients were female, average age of 43.5, and were followed for, on average 93 months in clinic. They were further stratified into axial (23.4%), axial and peripheral (62.6%) and peripheral (14%) SpA subtypes. 79 patient lab samples were also reviewed and showed that MEFV variant M694V homozygote was the most common (44.3%.) Researchers also found that 56% of patients had hip involvement and 23.3% of those patients had undergone total joint replacement. 

Hip arthritis was found to be higher in patients with two MEFV variants and in those who were M694V homozygous. Total joint replacement was higher in patients with M694V. HLA B27 positivity was lower in patients with FMF/SpA compared to controls. 

These two abstracts provide a glimpse into the unknowns in patients with FMF and SpA. We still have many questions regarding these diseases, both individually and in concert. 

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