We have found that patients with Fabry disease have an increased resting global cerebral blood flow compared with healthy subjects. This augmentation may result from an abnormal metabolic activity in the brain of the patients. The goal of this protocol is to study the cerebral metabolic rate of glucose (rCMRGlu) in eight untreated patients with Fabry disease, eight Fabry patients who are receiving enzyme replacement therapy and compare it with the rCMRGlu eight in healthy volunteers. In order to minimize the need for arterial lines we shall image the left ventricle of the heart to obtain the (18)FDG time-activity curve needed to measure rCMRGlu. The method will be validated in the healthy volunteers.