The unsolved mystery of MEFV variants variable expressivity in Familial Mediterranean Fever

The enigma of familial Mediterranean fever: phenotypic characterization of patients harbouring variants of uncertain significance

OBJECTIVE

To assess the phenotypic characteristics of the patients carrying variants of uncertain significance (VUS) in the Mediterranean fever (MEFV) gene.

METHODS

The study included patients carrying only VUS in the MEFV gene. Patients were excluded if they did not meet the paediatric criteria for familial Mediterranean fever (FMF). Patients were assigned to homozygous, compound heterozygous or heterozygous groups according to their genotype. Additionally, analyses were conducted based on specific genotypes.

RESULTS

A total of 2326 MEFV gene records were reviewed. Of these, 310 (F: 152/M: 158) met the inclusion criteria for analysis. The mean age at diagnosis and symptom onset was 7.51 ± 3.9 and 6.03 ± 3.86 years, respectively. Among the patients, 75.5% had a single variant, 17.1% were compound heterozygous, and 7.4% were homozygous. The common VUS alleles accounted for 93% of the cohort: E148Q (65.7%), P369S (15.6%), R408Q (7.6%) and A744S (4.1%). Most cases exhibited mild disease severity, while those with multiple variants were more likely to experience moderate disease severity. Patients with a homozygous allele had a higher mean number of annual attacks (11.2/year), a higher Pras severity score (5.86) and a greater proportion of moderate disease severity (56.5%). The most common clinical manifestations were abdominal pain (90.6%), fever (84.2%) and arthralgia (58.7%).

CONCLUSION

Individuals with VUS variants in the MEFV gene may present with a classic FMF phenotype characterized by mild to moderate disease activity. Patients carrying various VUS genotypes in the MEFV gene exhibit comparable clinical features with some degree of variation.

Unraveling the genome: Familial Mediterranean fever

ABSTRACT

Familial Mediterranean fever (FMF) is an inherited, autoinflammatory disease with a high prevalence in Middle Eastern and Mediterranean populations including Turks, Iranian, Spanish, Sephardic Jews, Arabs, and other Mediterranean ethnic groups. Autoinflammatory diseases are genetically predetermined disorders with multisystem effects primarily caused by defects in innate immunity. Although primarily known for an autosomal recessive mode of inheritance, there are increasing case reports associated with single Mediterranean fever (MEFV) mutation or dominant transmission. There have been over 300 variants identified in the MEFV gene; however, roughly 9-11 variants are responsible for the phenotypical expression seen with FMF. Symptoms include recurrent episodes of fever of unknown origin, abdominal, chest, or joint pain because of serosal inflammation. Persistent elevations in serum amyloid A can lead to complications like renal amyloidosis, kidney dysfunction, and end-stage kidney disease. Familial Mediterranean fever is diagnosed clinically using the Tel-Hashomer criteria and confirmed through genetic testing. Treatment includes initiation of colchicine with the goal of stopping attacks and preventing renal dysfunction and end-stage kidney disease. Genetic testing helps to identify the specific mutation allowing the provider to create a patient-specific treatment plan, monitor for complications such as renal amyloidosis, and enhance knowledge on the genetic heterogeneity and possible epigenetic factors.