Vitamin D binding protein genotype frequency in familial Mediterranean fever patients

Objective: Familial Mediterranean fever (FMF) is an autosomal recessive disorder characterized by recurrent short episodes (1-3 days) of inflammation and fever. FMF is associated with MEFV gene mutations but some patients with FMF symptoms do not have a mutation in the coding region of the MEFV gene. Vitamin D binding protein (VDBP) has important functions, including transporting vitamin D and its metabolites to target cells. Circulating levels of vitamin D are decreased in several inflammatory conditions, including FMF. Thus, we hypothesize that VDBP may play a crucial role in FMF pathogenesis, in addition to the MEFV gene. Method: VDBP genotyping was performed by polymerase chain reaction (PCR)-restriction fragment length polymorphism in 107 FMF patients and 25 healthy individuals without FMF or family history. For this, after amplification of genomic DNA, PCR products were digested with restriction enzymes HaeIII and StyI and evaluated electrophoretically. Results: We observed a statistically significant difference in the frequency of the 1F-2 genotype. The frequency of allele 2 was significantly higher and allele 1S was significantly lower compared to the [MEFV(-)] group and healthy controls (p = 0.034, 0.001, and 0.012, respectively). We observed a significant association between the presence of allele 2 and amyloidosis (p = 0.026) and arthritis (p = 0.044) in the [MEFV(-)] group. Conclusion: Our results suggest that FMF symptoms in the absence of MEFV gene mutations may be due to the presence of VDBP allele 2. Therefore, VDBP genotype may explain the symptoms in FMF [MEFV(-)] patients.