Abstract
BACKGROUND: Recent genetic association studies have investigated the possible genetic role of the dopaminergic system in migraine. Catechol-O-methyltransferase (COMT) is an enzyme that plays a crucial role in the metabolism of dopamine and its genetic polymorphism is associated with three- to fourfold variation of enzymatic activity. OBJECTIVES: The objective of this study was to elucidate the role of the COMT polymorphism in the genetic susceptibility to migraine and its phenotypic expression in patients with migraine without aura (MWOA). METHODS: Ninety-seven patients with MWOA and 94 healthy volunteers were included in the study. After amplifying COMT genes by the polymerase chain reaction, we assessed their genotype frequencies and allele distributions by based on restriction fragment length polymorphisms. We classified all MWOA patients into two groups according to their COMT genotype: with the L allele (N = 43), and without this allele (N = 54). RESULTS: The genotype frequency and allele distribution of the COMT polymorphism did not differ between MWOA patients and the control group. During migraine attacks, MWOA patients with the L allele showed a higher pain intensity of headache (P = 0.001) and a higher incidence of the accompanying nausea/vomiting (94% vs 75%; P = 0.026) compared with MWOA patients without the L allele. CONCLUSIONS: Although the COMT polymorphism does not appear to be involved in predisposition to the development of MWOA, this genetic factor could be involved in the phenotypic expression of MWOA.