Horner syndrome associated with ipsilateral facial and extremity anhydrosis.

We report a patient with Horner syndrome together with anhidrosis affecting the ipsilateral face and extremities confirmed with starch-iodine and sympathetic skin response testing. No anatomic lesion was apparent. This is the first reported case in which Horner syndrome has been associated with such extensive hemibody sympathetic dysfunction in the absence of other neurologic findings. We propose a developmental disorder of neural crest migration as the cause.