Significantly elevated plasma levels of homocysteine, but not cysteine and
cysteinylglycine, were found in treated parkinsonian patients compared to c
ontrols. Elevated levels of homocysteine may be either caused by an unknown
endogenous metabolic disturbance or by antiparkinsonian treatment, because
no association to severity or duration of disease was found. Based on the
results of this study one may speculate that homocysteine may be an indepen
dent risk factor for vascular disease in Parkinson's disease.