Neurochemical studies of CSF metabolites suggest a negative correlation between the dopamine metabolite homovanillic acid (HVA) and VH in a small number of LBD patients and weak negative correlations with aspartate and taurine in AD.32 One suggestion is that VH susceptibility is linked to a specific 3,4-dihydro-xyphenylacetic acid-HVA metabolic deficit, possibly as a result of a common polymorphism in the catechol-O-methyltransferase (COMT) gene. Here, COMT is linked to Alzheimer disease.