Idiopathic localized unilateral hyperhidrosis in a child.

Idiopathic unilateral circumscribed hyperhidrosis is an extremely rare form of increased sweat production that occurs within a sharply demarcated area on the face or upper extremities of otherwise healthy patients. There are no associated neurovascular or metabolic abnormalities. We report idiopathic localized unilateral hyperhidrosis on the upper extremity of a healthy 4-year-old girl.