Five patients with postural hypotension were evaluated for sweating defects. Three of the five were found to have anhidrosis. Two of these three had generalized anhidrosis and the other had partial anhidrosis. This combination of postural hypotension and anhidrosis represent the basic features of the autonomic insufficiency syndrome. Whether the primary defect of this syndrome resides within the central nervous system or the peripheral autonomic nervous system cannot be definitely determined in most cases. Intradermal injection of methacholine yielded inconsistent results, one patient being unresponsive to this agent and the others having a low normal sweat response. Hence, a positive sweat response to intradermal parasympathomimetic agents does not rule out anhidrosis; environmental testing is essential for this purpose. Blood pressures taken while the patient is in recumbant and standing positions should be determined in any patient with either localized or generalized anhidrosis.
Fisher DA, Maibach HI. Postural Hypotension and AnhidrosisThe Autonomic Insufficiency Syndrome. Arch Dermatol. 1970;102(5):527-531. doi:10.1001/archderm.1970.04000110043007