There is a need for better definition of polyarteritis nodosa (PAN) subphenotypes and the influence of ethnicity and geography. This study is aimed to study the demographic and clinical features of PAN cohorts from the UK and Turkey (TR) and to compare and contrast disease characteristics. A retrospective survey of databases from two vasculitis centres between 1990 and 2016 for PAN patients fulfilling the EMEA Vasculitis Classification algorithm. All paediatric-onset adult patients met the Ankara 2008 (EULAR/PReS endorsed) criteria for childhood PAN. Those with typical angiographic and/or histopathologic findings consistent with PAN were included. 93 (M/F: 51/42) patients (UK: 47, TR: 46) were included. Three were HBV-related, 20 (21.5%) had paediatric onset and 16 (16.5%), cutaneous PAN. TR patients had younger age of disease onset 44 (28.5-59.0) vs. 24.5 (11.8-40.5), p = 0.002. Twelve (26%) of TR patients had monogenic disease (Familial Mediterranean Fever association (n = 7), deficiency of adenosine deaminase 2, DADA2, (n = 5). No difference was found in phenotype between paediatric and adult onset patients except for frequency of cutaneous lesions (p = 0.002). During a median 67.5 (32-126) months follow-up, 13 patients died (12.7% in UK vs. 15.2% in Turkish cohorts). No difference was found between two cohorts in relation to relapse rate, death and vasculitis damage index. This study defined a diagnosis of PAN according to the EMEA algorithm. The TR group had a younger age of disease onset and more cases of monogenic disease; however, disease extent, relapse rate, damage index and death rates were similar between groups.

Migraine pathogenesis involves a complex interaction between hormones, neurotransmitters, and inflammatory pathways, which also influence the migraine phenotype. The Mediterranean fever gene (MEFV) encodes the pyrin protein. The major role of pyrin appears to be in the regulation of inflammation activity and the processing of the cytokine pro-interleukin-1β, and this cytokine plays a part in migraine pathogenesis. This study included 220 migraine patients and 228 healthy controls. Eight common missense mutations of the MEFV gene, known as M694V, M694I, M680I, V726A, R761H, K695R, P369S, and E148Q, were genotyped using real-time polymerase chain reaction with 5\' nuclease assays, which include sequence specific primers, and probes with a reporter dye. When mutations were evaluated separately among the patient and control groups, only the heterozygote E148Q carrier was found to be significantly higher in the control group than in the patient group (P=0.029, odds ratio [95% confidence interval] =0.45 [0.21-0.94]). In addition, the frequency of the homozygote and the compound heterozygote genotype carrier was found to be significantly higher in patients (n=8, 3.6%) than in the control group (n=1, 0.4%) (P=0.016, odds ratio [95% confidence interval] =8.57 [1.06-69.07]). However, there was no statistically significant difference in the allele frequencies of MEFV mutations between the patients and the healthy control group (P=0.964). In conclusion, the results of the present study suggest that biallelic mutations in the MEFV gene could be associated with a risk of migraine in the Turkish population. Moreover, MEFV mutations could be related to increased frequency and short durations of migraine attacks (P=0.043 and P=0.021, respectively). Future studies in larger groups and expression analysis of MEFV are required to clarify the role of the MEFV gene in migraine susceptibility.