Harlequin sign (hemifacial flushing and contralateral hypohidrosis) in a 4-year-old girl with Horner syndrome.

We report a Japanese infant with Horner syndrome whose clinical examination and testing suggested the location of the causative lesion. A 4-year-old Japanese girl had an acquired right ocular ptosis and unequal pupils presenting shortly after birth. She also exhibited left hemifacial flushing and loss of sweating on the contralateral side (harlequin sign). Physical examination demonstrated 2.0 mm of ptosis of the right upper lid with normal elevator function. The diameters of the pupils were 4 mm on the left and 2.5 mm on the right. No sweating was induced in the right frontal region at 40 degrees C for 15 minutes of sweat challenge test. Otherwise, no abnormalities were found by the neurophysiologic examinations or magnetic resonance imaging of the brain. Based on the clinical examination, we speculated that the responsible lesion might be in the preganglionic areas. Harlequin sign was informative for making the diagnosis of Horner syndrome.