Unresolved Issues in Familial Mediterranean Fever: Is p.R202Q MEFV Variant Potentially Pathogenetic in Unleashing Inflammation?

Familial Mediterranean Fever (FMF) is caused by mutations in the MEFV gene, which encodes for pyrin. Although genetic testing is commonly employed for FMF diagnosis, the interpretation of genetic results is often challenging. Therefore, we aimed to functionally characterise the p.R202Q MEFV alteration. Furthermore, we hypothesized that inflammation may affect genomic stability and neutrophilic (N) subsets. A cohort comprising patients with FMF (n = 4), p.R202Q variant (n = 18) and FMF-like (n = 8) were selected from the Outpatient Clinic for Autoinflammatory diseases of Padova University Hospital. Primary monocytes were incubated for 3 h in the presence of LPS or LPS + PKN1/2 inhibitor (UCN-01). Colchicine pretreatment was applied to assess its anti-inflammatory effect. Pro-inflammatory cytokines were measured by ELISA and leukocytes were examined using May-Grünwald-Giemsa staining on blood smears. We did not find significant differences in IL-1 and IL-18 levels in monocytes treated with LPS + UCN-01 between p.R202Q patients and healthy donors (HDs). The levels of IL-1β released from LPS-stimulated patients were higher in p.R202Q patients than in HDs. We found that immature and hypersegmented neutrophils were higher in p.R202Q patients than in HD. Nuclear abnormalities were higher in FMF and p.R202Q patients than in HD. Finally, we found a higher cell rate in leukocytes from p.R202Q patients than in HDs. The p.R202Q variant did not appear to affect pyrin function, albeit these patients presented cytological alterations similar to those observed in FMF patients. These changes may contribute to FMF pathophysiology by influencing inflammation progression.