Phenylthiocarbamide (PTC) perception in Parkinson disease

Objective: To examine phenylthiocarbamide (PTC) sensitivity in Parkinson disease (PD) patients and healthy volunteers to determine whether taster status represented a simple vulnerability marker for PD. Background: The inability to taste PTC has been associated with a number of medical illnesses not typically associated with taste impairment. Abnormalities in the function/expression of G protein-signaling pathways have been implicated in PTC perception and also in dopamine expression and regulation in PD. No study has yet probed whether PTC tasting is disrupted in PD. Method: PTC sensitivity was assessed in a small sample of 36 male PD patients and 20 healthy male comparison subjects using a standardized psychophysical method. Results: A higher proportion of nontasters were found in patients relative to healthy comparison subjects. These differences were not explained by alterations in perception of basic taste intensity or age. Among patients, nontasters and tasters of PTC did not differ with regard to duration of illness, age of onset, severity of motor symptoms, or overall illness severity. Conclusions: These data suggest an increase in the frequency of PTC nontaster status in PD. As phenotypic variation in PTC sensitivity is genetic in origin, this may represent a surrogate risk factor for the development of PD.