Relationship between COMT gene genotypes and severity of fibromyalgia

Background and aim: To determine the possible relationship between Val158Met genotypes of the COMT gene and the severity of fibromyalgia (FM) syndrome. Patients and methods: The study included 110 patients aged between 45 and 55 years old diagnosed with FM (ACR, 1990) and 110 samples from control subjects with no pain and no abnormal fatigue (National DNA Bank, Spain). To measure the severity of fibromyalgia, the Fibromyalgia Impact Questionnaire (FIQ) was used. Severe FM was defined as an FIQ of ≥ 70 and was found in 35.5% of the patients. Polymorphisms were analyzed using standard polymerase chain reaction techniques. All the groups met the Hardy-Weinberg equilibrium. Results: The frequency of the Met/Met genotype was lower in controls (20.9%) than in patients (34.5%), whereas that of the Val/Val genotype was higher in controls (30.9%) than in patients (20.0%), with significant differences (p = 0.048). The mean FIQ values were higher in the Met/Met genotypes (71.67) and Val/Met genotypes (68.27) and were lower in the Val/Val genotype (58.93). Tukey's multiple comparison test indicated that FIQ values presented significant differences when Met/Met/ Val/Val (Tukey, p < 0.001) and Val/Val/Val/Met (Tukey, p=0.003) were compared. Conclusions: Our results appear to indicate that the Met/Met genotype is associated with greater severity of FM symptoms.