The analysis of genotype-phenotype correlation in familial Mediterranean fever

The Impact of Different MEFV Genotypes on Clinical Phenotype of Patients with Familial Mediterranean Fever: Special Emphasis on Joint Involvement

Familial Mediterranean Fever (FMF) is the most common monogenic autoinflammatory disease worldwide. In this retrospective cohort study, we aimed to assess the effects of various MEFV genotypes on the clinical characteristics of the patients, with a special focus on the joint involvement. In total, 782 patients with FMF were categorized into 3 groups according to the MEFV mutation; Group 1: Patients homozygous for M694V; Group 2: Patients carrying other pathogenic MEFV variants in exon 10 in homozygous or compound heterozygous states; and Group 3: FMF patients with other variants or without mutations. Clinical and demographic findings were compared between groups. Among the 782 FMF patients, total frequency of arthritis was 237 (30.3%): 207 (26.4%) were acute monoarthritis and 67 (8.5%) were chronic arthritis. Both the frequency of arthritis (acute and/or chronic) (40.4% vs. 24.8% vs. 26.7%; p:0.001) and acute monoarthritis (35.4% vs. 20% vs. 23.7%; p:0.001) were significantly higher in Group 1 than in the other groups. FMF patients with chronic arthritis showed a distinct juvenile idiopathic arthritis (JIA) distribution pattern with a more frequent enthesitis-related arthritis (ERA) subtype (43.2%). HLA-B27 was positive in 24% of the ERA patients.Conclusion: Homozygous M694V mutation is associated with a more frequent and longer acute monoarthritis comparing to other MEFV genotypes. In addition, the risk of chronic arthritis seems not related to the MEFV mutations. However, FMF patients with chronic arthritis show a distinct ILAR JIA distribution pattern with a more frequent ERA and undifferentiated arthritis subtype. What is known: • Homozygous M694V mutation is associated with a more frequent and longer acute monoarthritis What is new: • FMF patients with chronic arthritis show a distinct ILAR JIA distribution pattern with a more frequent ERA subtype • ERA patients with negative HLA-B27 antigen should also be assessed for polyserositis episodes of FMF, especially in countries with high FMF carrier frequency.

The significance of carrying MEFV variants in symptomatic and asymptomatic individuals

Familial Mediterranean fever (FMF) is an autoinflammatory disease characterized by recurrent attacks of fever, serositis (peritonitis, pleuritis, or synovitis), and erysipelas-like erythema. Genetic variants in the MEFV gene are associated with this disease. Familial Mediterranean fever is considered an autosomal recessive disease. However, in Middle Eastern countries, a third of the patients expressing FMF manifestations, carry a single mutation only. Moreover, some cases of pure dominant inheritance linked to specific single MEFV variants have also been described. This complex inheritance of MEFV-associated inflammatory diseases poses a serious challenge when interpreting the results of genetic testing in patients having recurrent fever syndromes. In addition, in certain situations, asymptomatic individuals may be incidentally found to carry MEFV variants. These cases pose the question of their exact diagnosis and whether they should be treated. Previous studies have focused on genetic results interpretations among symptomatic patients. In the current article, we would like to elaborate on the genetic interpretation in cases of symptomatic individuals suspected to have FMF and on asymptomatic individuals carrying MEFV variants. We aim to assist physicians unfamiliar with FMF to cope with genetic results interpretation when facing symptomatic and asymptomatic individuals carrying MEFV variants and suggest a management plan accordingly.

Pyrin Inflammasome Activation Defines Colchicine-Responsive SURF Patients from FMF and Other Recurrent Fevers

Syndrome of undifferentiated recurrent fever (SURF) is characterized by recurrent fevers, a lack of confirmed molecular diagnosis, and a complete or partial response to colchicine. Despite the clinical similarities to familial Mediterranean fever (FMF), the underlying inflammatory mechanisms of SURF are not yet understood. We here analyzed the in vitro activation of the pyrin inflammasome in a cohort of SURF patients compared to FMF and PFAPA patients. Peripheral blood mononuclear cells (PBMC) were collected from SURF (both colchicine-treated and untreated), FMF, PFAPA patients, and healthy donors. PBMC were stimulated ex vivo with Clostridium difficile toxin A (TcdA) and a PKC inhibitor (UCN-01), in the presence or absence of colchicine. The assembly of the pyrin inflammasome was evaluated by measuring the presence of apoptosis-associated Speck-like protein containing caspase recruitment domain (ASC) specks in monocytes using flow cytometry. IL-1β secretion was quantified using an ELISA assay. No differences in TcdA-induced activation of pyrin inflammasome were observed among FMF, PFAPA, and healthy donors. Untreated SURF patients showed a reduced response to TcdA, which was normalized after colchicine treatment. In contrast to FMF, SURF patients, similar to PFAPA patients and healthy donors, did not exhibit pyrin inflammasome activation in response to UCN-01-mediated pyrin dephosphorylation. These data demonstrate that in vitro functional analysis of pyrin inflammasome activation can differentiate SURF from FMF and PFAPA patients, suggesting the involvement of the pyrin inflammasome in the pathophysiology of SURF.

Genetic and clinical features of familial mediterranean fever (FMF) in a homogeneous cohort of patients from South-Eastern Italy

Familial Mediterranean Fever (FMF) is linked with the MEFV gene and is the commonest among monogenic autoinflammatory diseases, with high prevalence in the Mediterranean basin. Although the clinical presentation of FMF has a major role in diagnosis, genotype/phenotype correlations and the role of "benign" gene variants (as R202Q) appear highly variable and incompletely clear, making difficult to select the most effective strategy in the management of patients. Aim of the present study was to investigate the clinical presentation and the genetic background in a homogenous cohort of patients from Apulia (south eastern Italy). We investigated 217 patients with a clinical suspect of autoinflammatory diseases, who were characterized for the occurrence of specific symptoms and with next generation sequencing by a 4-gene panel including MEFV, MVK, NLRP3 and TNFRSF1A. A genetic change was identified in 122 (53.7%) patients, with 161 different MEFV variants recorded in 100 individuals, 10 variants in NLRP3, and 6 each in TNFRSF1A and MVK. The benign variant R202Q was largely prevalent (41.6% of all MEFV variants). When patients were selected according the number of pathogenic MEFV variants (0, 1, or 2 pathogenic variants), results failed to show significant links between the frequency of symptoms and the number of pathogenic variants. Only family history and Pras score (indicative for severity of disease) predicted the presence of pathogenic variants, as compared with carriers of variants considered of uncertain significance or benign. Fever >38 °C and arthralgias appeared more frequently in R202Q-positive patients than in non-R202Q carriers. These two subgroups showed comparable duration of fever, occurrence of myalgia, abdominal and chest pain, Pras, and IFFS scores. In conclusion, results confirm that FMF manifests in mild form in non-middle eastern patients. This possibility partly affects the reliability of clinical criteria/scores. Furthermore, the presence of the R202Q variant might not be completely neutral in selected groups of patients.

Real-Life Data From the Largest Pediatric Familial Mediterranean Fever Cohort

Familial Mediterranean fever (FMF) is the most common monogenic autoinflammatory disease manifesting phenotypic heterogeneity. It is a clinically diagnosed disease supported by MEditerranean FeVer (MEFV) gene mutation analysis. However, the phenotype-genotype correlation is not yet established clearly. We aimed to determine the clinical findings, phenotype-genotype correlation, and treatment outcomes within a large pediatric FMF cohort. The medical charts of children with FMF who were diagnosed and followed up at the eight pediatric rheumatology units were reviewed retrospectively. All patients in the cohort were analyzed for sequence variants in exon 2,3,5 and 10 of the MEFV gene. Patients without any mutations or with polymorphisms including R202Q were excluded. A total of 3,454 children were involved in the study. The mean ± standard deviation of current age, age at symptom onset, and age at diagnosis were 12.1 ± 5.2, 5.1 ± 3.8, and 7.3 ± 4.0 years, respectively. Of 3,454 patients, 88.2% had abdominal pain, 86.7% had fever, 27.7% had arthritis, 20.2% had chest pain, 23% had myalgia, and 13.1% had erysipelas-like erythema. The most common MEFV mutation patterns were homozygous (32.5%) and heterozygous (29.9%) mutations of exon 10. Homozygous M694V was present in 969 patients (28.1%). Allele frequencies of common mutations were M694V (55.3%), M680I (11.3%), V726A (7.6%), and E148Q (7.2%). Children carrying homozygous or compound heterozygous exon 10 mutations had an earlier age of disease onset (4.6 vs. 5.6 years, p = 0.000) and a higher number of attacks per year (11.1 vs. 9.6, p = 0.001). Although 8% of the patients had a family history of amyloidosis, 0.3% (n = 11) had the presence of amyloidosis. M694V homozygosity was detected in nine patients who developed amyloidosis. Colchicine resistance was present in 4.2% of our patients. In this largest pediatric cohort reviewed and presented to date, patients with exon 10 mutations, particularly the M694V homozygous mutation, have been demonstrated earlier disease onset, annual attack count, and more frequent colchicine-resistant cases. Although E148Q is considered as a polymorphism in some populations, it was identified as a disease-causing mutation in our cohort. Secondary amyloidosis is still happening in adults however, it is extremely rare among children, presumably due to increased awareness, tight control, and the availability of anti-IL1 agents in colchicine-resistant cases.