In Fabry disease, an X-linked alpha-galactosidase A deficiency, painful crises and limb paresthesias are possibly linked to thermal exposure. Small nerve fiber function has not yet been tested after cold challenge. In two Fabry patients (15 and 17 years old), their heterozygote mother, their healthy sister, and eight controls, we determined warm and cold perception thresholds at the dorsal foot and the lower medial calf (method of limits, Somedic-Thermotest), before and 1, 5, 10 and 15 min after 30 s immersion of one leg into 5 degrees C water. Discomfort was rated from 0 to 10. At baseline, thermal thresholds of all participants were normal. In contrast to controls, the patients tolerated 30 s cold stimulation only with interruptions. The mother aborted stimulation after 6 s because of pain. The patients and their mother reported intense burning pain and numbness during and after stimulation. After cold exposure, thermal sensation was highly abnormal for 20 min in one and 80 min in the other brother. In controls, thermal thresholds were somewhat elevated after stimulation but normalized within 10.0+/-4.6 min. Discomfort during cold exposure was rated 8-10 by the patients and their mother, but 3-5 by the healthy persons. We assume that glycolipid accumulation in cutaneous and vasa nervorum vessels as well as small nerve axons accounts for skin and small fiber malperfusion during cold induced vasoconstriction. Transitory ischemia initiated burning pain and prolonged small fiber dysfunction.