Dermal microdialysis provides evidence for hypersensitivity to noradrenaline in patients with familial dysautonomia

Objectives: To use the technique of dermal microdialysis to examine sensitivity of skin vessels to noradrenaline (NA) in patients with familial dysautonomia (FD) and in healthy controls. Methods: In 14 patients with FD and 12 healthy controls, plasma extravasation, local laser Doppler blood flow, and skin blanching were observed before, during, and after application of 10^-6 M NA through a microdialysis membrane, located intradermally in the skin of the lower leg. Results: Maximum local vasoconstriction measured by laser Doppler blood flow did not differ between patients with FD and controls. In contrast, patients with FD had an earlier onset of vasoconstriction (p = 0.02). Moreover, reaction to NA was more prominent and prolonged in FD, shown by a larger zone of skin blanching around the microdialysis membrane (p < 0.001) and delayed reduction of the protein content in the dialysate after termination of NA application (p = 0.03). Conclusion: These data support the hypothesis that peripheral blood vessels of patients with FD show a denervation hypersensitivity to catecholamines. This may be one mechanism contributing to the major hypertension that frequently occurs during "dysautonomic crises" in FD.