A purine degradation study, thermography and near infrared spectroscopy of the extremities were performed on 2 young males with Fabry disease and 2 healthy controls. Two-minute semi-ischemic forearm exercise caused a distinct increase in lactate in all subjects, but venous hypoxanthine and ammonia were greatly increased only in the Fabry patients, suggesting a relatively hypoxic state of the extremities. Limb thermograms of the patients revealed glove and stocking type disturbance at rest. Poor recovery of the skin temperature of the hands and forearms after exercise was observed in the patients, but the sharp increase in oxygenated hemoglobin after total ischemia was found to be normal or near infrared spectroscopy. Neurotropin showed an analgesic effect, i.e. a strong and selective heat-productive action on the painful lesions, and suppressed the hypoxanthine level after exercise in 1 patient. Although the pathophysiology of the pain in Fabry disease has not been clearly elucidated, a relatively hypoxic state with peripheral hypothermia might play an important role in triggering of a painful attack or chronic burning paresthesia.