COMT and Parkinson disease: Studies from Portland [1, 12] (including 322 patients with PD and 357 controls) did not demonstrate an association between functional COMT haplotypes in patients with PD and the controls; the frequencies of low (A_C_C_G) and medium (A_T_C_A) or without high (G_C_G_G) activity haplotypes tended to be slightly lower among patients with PD than among the controls.