A 49-year-old man had frequent episodes of heat exhaustion and excessive sweating involving the left lower quadrant of his back, associated with lack of sweating on his forehead, axilla, hands, and feet. He also had difficulty focusing with his left eye.

Our patient had episodes of heat exhaustion associated with hyperhidrosis and segmental anhidrosis. He also had problems with accommodation of his left eye. Examination was remarkable for anisocoria (left pupil larger than right pupil) with absent reaction to light but with a slow constriction to prolonged near effort (lightnear dissociation). Redilation after constriction (not shown) was slow and tonic. The patellar and ankle reflexes were absent.