INCREASED FREQUENCY OF MEFV GENES IN PATIENTS WITH EPIGASTRIC PAIN SYNDROME
Coskun BD, Kiraz A, Sevinc E, Baspinar O, Cakmak E
*Corresponding Author: Banu D. Coskun, M.D., Kicikapı Mahallesi Hoca Ahmet Yesevi Cad Hidayet Eraslan sitesi B Blok No: 12, Talas/Kayseri Turkey. Tel: +90-506-323-24-86. Fax: +90-352-437-52-73. E-mail: demetcoskun2@gmail.com
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DISCUSSION

Our study aimed to determined the frequency of MEFV gene mutations and FMF clinical findings in patients who were followed with a diagnosis of EPS. Familial Mediterranean fever is an autoinflammatuar disease characterized by recurrent and self-limited episodes of fever, abdominal pain and serositis with a duration of 1-3 days. The prevelance of FMF is 1/1000 and the carrier rate is 15.0-34.0% in Turkey [3,4]. It is caused by mutations in the MEFV gene. More than 300 mutations of the MEFV gene have been reported [11]. A diagnosis of FMF was established according to clinical criteria (Tel Hashomer criteria), rather than genetic analysis [12,13]. However, genetic analyses are helpful in detecting atypical FMF presentations, presymptomatic patient’s relatives and confirmation of the FMF diagnosis [14]. There are also many studies indicating that there are FMF patients who do not carry MEFV gene mutations (10.0-20.0%) [15,16]. In the present study, EPS patients were evaluated according to both the Tel Hashomer criteria and genetic analysis for the diagnosis of FMF. The FMF diagnosis has not been established in EPS patients who do not carry MEFV gene mutations. The most commonly seen mutations in FMF patients are M694V, M680I (G/C), E148Q, V726A, and frequency of the mutations change according to ethnicity [17,18]. Erden et al. [19] reported that 68.6% of FMF patients had at least one of the several mentioned mutations: M694V; 46.2%, E148Q; 16.4%, V726A; 13.4% and M680I; 5.9%. In our study population, 43 EPS patients (57.3%) had MEFV gene mutations and the carrier rate was 30.0%. The most common mutation was R202Q (55.0%), followed by E148Q (16.2%), R761H (16.2%), V726A (9.3%), M680I (9.3%) and M694V (4.6%). While the frequency of M694V, which is the most commonly observed MEFV gene in Turks, was quite low, the frequencies of other genes were approximately consistent with previous studies [20,21]. The different frequency distribution of mutations may be related to the small sample size, the geographical region, genetic heterogeneities, patients’ inclusion criteria, and the use of different genetic analytical techniques. The R202Q was another common mutation in the Turkish population. Some studies have also recently reported that frequency of R202Q was higher than the frequency of the M694V mutation in FMF patients [22,23]. In a study by Yigit et al. [24] conducted on 191 FMF patients and 150 control patients; the frequency of the R2O2Q mutation was higher than that found for the M694V mutation. The frequency of heterozygous R202Q was similar between FMF patients and controls (59.7 vs. 44.7%; p >0.05), while the frequency of homozygous R202Q mutations was higher than that in the controls (14.7 vs. 0.0%; p <0.05) [24]. Giaglis et al. [25] reported that homozygous R202Q was detected in 14/152 (9.2%) FMF patients and in 1/140 (0.7%) in a Greek study population. They also reported that the heterozygous state of R202Q produced no symptoms and only the homozygous and compound heterozygous states were associated with the development of symptoms [25]. In present study, the most common MEFV gene mutation in EPS patients was R202Q. In our geographic region, MEFV genetic analysis showed that R202Q gene mutations in FMF patients and healthy controls were not found. However, contrary to the above data, Comak et al. [26] found that some patients with a heterozygous R202Q mutation had typical episodes of FMF. In addition, Cankaya et al. [27] compared the clinical symptoms between R202Q/– and non-R202Q/– in FMF patients. It was shown that there were no differences in the frequencies of symptoms and definitive diagnosis of FMF in either group. In our study of 24 EPS patients with the R202Q gene mutation, 15 were heterozygotes, three were homozygotes, two were compound heterozygotes, and four carried the compound heterozygotes for three mutations [27]. We did not find a homozygous R202Q in the control group, which was in agreement with results from previous studies. In our study, one patient with the heterozygous R202Q mutation had arthralgia, fever, and a familial history of FMF. While only one of the patients with the homozygous R202Q mutation had FMF clinical findings, the remainder were silent carriers. We also observed that there were no clinical symptoms in either R202Q/– or non-R202Q/– in EPS patients. E148Q and V726A are other commonly observed mutations in Turkish FMF patients. The carrier frequencies of E148Q and V726A have been reported as 12.0 and 3.0-14.0%, respectively. The frequency of E148Q in Turks is similar with other ethnicities [25,28,29], while V726A is especially common in Arabs [30]. Ben-Chetrit et al. [31] found a similar frequency of E148Q mutations between patients and controls and suggested that E148Q is a benign polymorphism. However, some authors accepted that E148Q was a pathogenic mutation because of substitution of the glutamine for glutamic acid at codon 148 in exon 2 [32]. Familial Mediterranean fever patients with homozygous and compound heterozygous mutations have moderate/severe disease. In addition, several studies reported that E148Q was also associated with vasculitis (Henosch-Schonlein purpura, polyarteritis nodosa) and rheumatic diseases [33]. In the present study, E148Q was the second most common mutation with a frequency of 16.2%. While one patient who was a compound heterozygote for three mutations (R202Q/E148Q/R408Q) had FMF symptoms, five patients heterozygous for E148Q/–, and one patient with a compound heterozygosity for two mutations (L110P/E148Q) had no FMF symptoms. V726A is associated with a mild form of the disease. However, V726A homozygotes and compound heterozygotes for the V726A/E148Q variants are associated with severe disease, and patients can develop renal amyloidosis. Hence, the authors proposed that patients carrying this complex allele should have been given colchicine prophylaxis [9,34]. In the present study, V726A is the third most common mutation with a frequency of 9.3%. While two patients who had compound heterozygosities for two or three mutations (V726A/K695R and V726A/M694V/ R202Q), presented with FMF symptoms, one patient with heterozygous V726A/– and one patient with a compound heterozygosity for V726A/M680I, did not. In this study, the rare MEFV gene mutations were also identified as K695R (2.3%), L110P (2.3%) and G304R (2.3%). Dogan et al. [35] reported that the frequency of rare mutations were identified as L110P (0.2%) and K695R (0.1%) in 731 participants. In another study, Gunesacar et al. [36] found that the frequency of rare mutations were as follows: K695R (0.20%), L110P (0.10%) and G304R (0.05%). Moreover, they also detected the G304R mutation for the first time in Turkey. To date, it has been detected in a total of 33 patients carrying K695R in Turkey. It has been reported in the literature that some patients carrying K695R (compound heterozygotes) have severe FMF sypmtoms [37]. L110P is a more common MEFV gene mutation in Japan and is associated with a milder form of the disease [38]. In the present study, two patients carrying rare MEFV gene mutations were diagnosed with FMF (K695R/V726A and G304R/–), and another patient (L110P) was asymptomatic. We also detected a second case carrying the G304R mutation in Turkey. Familial Mediterranean fever can be divided into three clinical phenotypes: type 1 or typical FMF phenotype (attacks of abdominal pain, arthritis, fever); type 2 characterized by the presence of amyloidosis in asymptomatic subjects and (incidence of 7.0-25.0%); type 3 ‘silent type’ homozygous or compound heterozygous state and is estimated to occur in 1:300 Ashkenazi and 1:25 Iraqi Jews. In recent years, it has been observed that heterozygous mutation carriers can suffer also from a mild or incomplete form of FMF, named ‘FMF-like’ disease (a new phenotype) [9]. In recent years, a new phenotype termed ‛FMF-like disease,’ which is characterized as a mild or incomplete form of FMF in patients with heterozygous mutations has been defined. The reason why some carriers experience FMF clinical symptoms, while others present with only mild or no symptoms, is largely unknown, but it is assumed that the MEFV gene mutations combined with other potential modifier genes and environmental factors determine the FMF phenotype [9,14]. Thus, we also speculated that the heterozygous state of the MEFV gene may be associated with the atypical inflammatory forms of FMF. Epigastric pain might be an incomplete FMF attack, and physicians should keep this in mind in high-risk populations. Treatment for asymptomatic individuals with heterozygous mutations is unknown. Guidelines recommend that they should be followed with urine analyses [39]. Familial Mediterranean fever-like disease may initiate periodic follow-up, and administering colchicine should be considered. The patients with the ‘silent’ carrier status of two mutations (homozygous or compound heterozygous) could predispose to developing renal amyloidosis, and particularly patients with a family history of FMF should be administered colchicine prophylaxis [40]. In our study, we started colchicine therapy for FMF patients and patients who have an asymptomatic homozygous R202Q mutation and family history of FMF for increased risk of developing amyloidosis. Conclusions. Our results demonstrated a high carrier rate of MEFV gene mutations in the EPS patients. The EPS patients showed only homozygous or compound heterozygous MEFV gene mutations. Eight patients with EPS were diagnosed with FMF and colchicine therapy was started. Thus, therapy-resistant EPS patients should also be examined for FMF, especially in high risk populations such as the Turks. However, additional and larger studies are needed to identify the association between EPS and FMF. Declaration of Interest. The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article.



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