Serotonin receptor (5-HT 2A) and catechol-O-methyltransferase (COMT) gene polymorphisms: Triggers of fibromyalgia?

Introduction: Fibromyalgia is a rheumatic syndrome characterized by diffuse and chronic pain associated with fatigue, sleep disorders, anxiety, depression, memory loss, and dizziness. Although the physiological mechanisms that control fibromyalgia have not been precisely established, neuroendocrine, genetic or molecular factors may be involved in fibromyalgia. Objective: The aim of the present study was to characterize serotonin receptor (5-HT2A) and catechol-O-methyltransferase (COMT) gene polymorphisms in Brazilian patients with fibromyalgia and to evaluate the participation of these polymorphisms in the etiology of the disease. Material and Methods: Genomic DNA extracted from 102 blood samples (51 patients, 51 controls) was used for molecular characterization of the 5-HT2A and COMT gene polymorphisms by PCR-RFLP. Results: Analysis of the 5-HT2A polymorphism revealed a frequency of 25.49% C/C, 49.02% TIC and 25.49% T/T in patients, and of 17.65% C/C, 62.74% TIC and 19.61% T/T in the control group, with no differences between the two groups. Analysis of the COMT polymorphism in patients showed a frequency of 17.65% and 45.10% for genotypes H/H and L/H, respectively. In the control group the frequency was 29.42% for H/H and 60.78% for L/H, also with no differences between the two groups. However, there was a significant difference in the frequency of the Lit genotype between patients (37.25%) and controls (9.8%), which permitted differentiation between the two groups. Conclusion: The L/L genotype was more frequent among fibromyalgia patients. Though considering a polygenic situation and environmental factors, the molecular study of the rs4680 SNP of the COMT gene may be helpful to the identification of susceptible individuals.