Progressive isolated segmental anhidrosis.

A patient had progressive segmental anhidrosis, which proved after extensive neurologic and autonomic workup to be an isolated abnormality. Intradermal acetylcholine produced localized sweating in areas of thermoregulatory anhidrosis five months after the onset of symptoms but failed to do so at two years. These findings are consistent with a preganglionic sympathetic lesion affecting a functionally defined subset of sympathetic cells and/or fibers. The alteration of the sudomotor response to intradermal acetylcholine during the course of the illness suggests that the diagnostic utility of pharmacologic sweat tests may be time dependent, limited to a relatively early period following onset of anhidrosis.