Blood-based test for diagnosis and functional subtyping of familial Mediterranean fever

Abstract

Background and objectiveFamilial Mediterranean fever (FMF) is the most common monogenic autoinflammatory disease (AID) worldwide. The disease is caused by mutations in the MEFV gene encoding the inflammasome sensor Pyrin. Clinical diagnosis of FMF is complicated by overlap in symptoms with other diseases, and interpretation of genetic testing is confounded by the lack of a clear genotype–phenotype association for most of the 340 reported MEFV variants. In this study, the authors designed a functional assay and evaluated its potential in supporting FMF diagnosis.MethodsPeripheral blood mononuclear cells (PBMCs) were obtained from patients with Pyrin-associated autoinflammation with an FMF phenotype (n=43) or with autoinflammatory features not compatible with FMF (n=8), 10 asymptomatic carriers and 48 healthy donors. Sera were obtained from patients with distinct AIDs (n=10), and whole blood from a subset of patients and controls. The clinical, demographic, molecular genetic factors and other characteristics of the patient population were assessed for their impact on the diagnostic test read-out. Interleukin (IL)-1β and IL-18 levels were measured by Luminex assay.ResultsThe ex vivo colchicine assay may be performed on whole blood or PBMC. The functional assay robustly segregated patients with FMF from healthy controls and patients with related clinical disorders. The diagnostic test distinguished patients with classical FMF mutations (M694V, M694I, M680I, R761H) from patients with other MEFV mutations and variants (K695R, P369S, R202Q, E148Q) that are considered benign or of uncertain clinical significance.ConclusionThe ex vivo colchicine assay may support diagnosis of FMF and functional subtyping of Pyrin-associated autoinflammation.

Therapeutic modulation of inflammasome pathways

“…Notably, disease-penetrant FMF mutations were recently shown to render Pyrin inflammasome activation independent of microtubules. 78,80…”

“…This feature appeared highly specific for FMF-associated mutations and was recently leveraged to develop a functional diagnostic assay for rapidly stratifying FMF patients. 80 Significantly lower doses of colchicine are being used in the clinic since the 1970' to effectively control FMF symptoms, but the therapeutic mode of action of colchicine in FMF and gout patients remains a mystery.…”

Familial Mediterranean Fever and COVID-19: Friends or Foes?

“…The E148Q and R202Q MEFV variants, which according to a current consensus are considered neutral polymorphisms, showed a response to colchicine challenge alike normal controls (42). These two variants presented rather divergent evolutionary features.…”

Familial Mediterranean fever, from pathogenesis to treatment: a contemporary review

“…Next generation sequencing (NGS) has identified many new variants but their clinical associations are largely unknown, hampering their interpretation. Functional assays and biomarkers that may aid in diagnosis, assessment of disease severity and treatment are under development [2]. Practical indices quantifying FMF disease severity, activity and recently damage accrual have been developed and validated for clinical use and research purposes [3][4][5].…”

“…MEFV gene has 10 exons and there are more than 370 variants identified to date. The number of variants are increasing with use of genome sequencing 2 . Most of the pathogenic/likely pathogenic variants are located on exon 10 which encodes B30.2/SPRY domain, responsible for the activation of caspase-1.…”