Increased prevalence of M694V in patients with ankylosing spondylitis: additional evidence for a link with familial mediterranean fever.

OBJECTIVE: To assess whether there is a statistically significant difference in the frequency of common MEFV allele variants in patients with ankylosing spondylitis (AS) as compared with control patients with rheumatoid arthritis (RA) and with healthy control subjects.
METHODS: Sixty-two patients with AS, 50 healthy control subjects, and 46 patients with RA were assessed for the presence of MEFV variants. Exon 10 was analyzed by direct sequencing. E148Q was analyzed by restriction endonuclease enzyme digestion (REED) or by direct sequencing when REED analysis failed.
RESULTS: The allele frequency of all MEFV variants in the AS group was significantly higher than that in the pooled control group of healthy subjects plus RA patients (15.3% versus 6.8%; P = 0.021). M694V was the only variant that was significantly more common in the AS group than in the combined or individual control groups (P = 0.026 for AS patients versus healthy controls, P = 0.046 for AS patients versus RA patient controls, and P = 0.008 for AS patients versus healthy and RA patient control groups). The carriage rate of M694V was also significantly higher in the AS patient group than in the combined control group (odds ratio 7.0, P = 0.014). Neither M694V nor any other MEFV variant showed a correlation with most of the disease-related measures examined.
CONCLUSION: We found an increased frequency of MEFV variants in AS patients as compared with healthy controls and with RA patient controls. This was primarily due to the presence of M694V. The roles of other exon 10 variants, as well as the relationship between the variant status and the severity and clinical course of the disease, need to be explored in further studies that include sufficiently large sample sizes.