Impaired skin vasomotor reflexes in patients with erythromelalgia

Erythromelalgia (EM) is a chronic disorder characterized by intermittent bu rning pain, warmth and erythema of the extremities. Increasing the local te mperature and dependency of the affected limb(s) precipitates the symptoms, whereas direct cooling and elevation of the limb(s) can provide partial re lief. Our previous findings showed that patients with EM have enhanced cuta neous vascular tone at rest and during stimulation, which may be due to an increase in sympathetic neural activity. To test this, we measured skin vas oconstrictor responses to contralateral arm cold challenge (CC) and inspira tory gasp (IG) using laser Doppler flowmetry at the toe pulp and fingertip. These areas were chosen because of their dense sympathetic innervation. An index of the vasoconstrictor response (between 0 and I) was calculated fro m the change in skin perfusion from baseline following CC and IG. In contro l subjects, vasoconstrictor responses to CC at the toe and fingertip were b oth 0.70+/-0.02 (mean +/-S.E.M.), which were significantly greater (P < 0.0 01) than corresponding values in patients with EM (0.37 +/- 0.04 and 0.45+/ -0.04 respectively). Similarly, vasoconstrictor responses to IG were signif icantly greater (P < 0.001) at the toe and fingertip in control subjects (0 .70+/-0.03 and 0.70+/-0.02 respectively) compared with values in EM patient s (0.27 +/- 0.03 and 0.45+/-0.15 respectively). These data show that, in co ntrast with control subjects, patients with EM have diminished sympathetic vasoconstrictor responses to both CC and IG. Denervation supersensitivity m ay play a part by increasing vasoconstrictor responses to circulating catec holamines, leading to a reduction in skin blood flow. Therefore an interpla y between neural and vasoactive agents may be involved in the pathophysiolo gy of EM.