Background: Systemic juvenile idiopathic arthritis (sJIA) has many clinical features overlapping with familial Mediterranean fever (FMF), which is caused by mutations in MEFV gene. And FMF patients were easily misdiagnosed as sJIA in China. So we speculate that MEFV is critical genetic background for sJIA and influences patients' severity. In this study, we aim to figure out whether MEFV mutations are risk factor for the occurrence of sJIA and to study the association of MEFV mutations with disease severity of sJIA patients.
Methods: The present study includes 57 sJIA children and 2573 healthy controls. Odd ratio with 95% confidence interval based on allelic frequency of MEFV mutations or variants was used to evaluate their contribution to sJIA susceptibility. Meta-analysis was then performed to reach comprehensive conclusion. All included sJIA patients were grouped by presence and number of MEFV mutations. Clinical data and indicators of disease severity were compared among different groups. Multiple linear regression method was used to find out whether the number of MEFV variants is associated with the severity of sJIA. Kaplan-Meier curves and log rank test were used to estimate the probability of the first relapse.
Results: The MEFV mutations of our subjects predominantly existed in exons 2 and 3. No significant difference was found in allelic frequency between sJIA children and healthy controls. Meta-analysis demonstrated that p.M694V/I was a risk factor for sJIA (pooled OR: 7.13, 95% CI: 3.01-16.89). The relative period of activity was significantly lower in the one mutation group than those with more than one mutation (p = 0.0194). However, no relevance was found in multiple linear regression models.
Conclusions: The mutation p.M694V/I in MEFV might be a risk factor for sJIA. SJIA patients carrying more than one heterozygous mutation in MEFV tend to be more severe than those containing only one, but studies in other cohort of patients need to be performed to validate it.
Keywords: Disease risk; Disease severity; MEFV gene; Systemic juvenile idiopathic arthritis.