Harlequin syndrome

Disease Overview

Harlequin syndrome is a syndrome affecting the autonomic nervous system.[13659] The autonomic nervous system is responsible for controlling the body’s natural processes such as sweating, skin flushing, and the response of the pupils to stimuli.[13660] People with Harlequin syndrome have the absence of sweating and flushing of skin on one side of the body (unilateral), especially of the face, arms, and chest.[13659][546]

The symptoms associated with Harlequin syndrome may be more likely to occur when a person has been exercising, is very warm, or is in an intense emotional situation.[13659] In these situations, one side of the body sweats and flushes appropriately as a response to the situation, whereas the other side of the body does not. The asymmetrical facial sweating and flushing associated with this condition has been named the “Harlequin sign.” Harlequin syndrome is thought to be one of a spectrum of diseases that can cause Harlequin sign.[5715]

The exact cause of Harlequin syndrome is not completely understood. In some patients with this syndrome, the underlying cause seems to be a lesion or tumor that is affecting the ability of the cells of the autonomic nervous system to communicate with one side of the body.[5715] However, in many cases an exact cause of the symptoms is not found.[7849]

Diagnosis of Harlequin syndrome is based on observing symptoms consistent with the syndrome, followed by a series of tests to rule out other diseases associated with Harlequin sign.[5715][7849] Treatment may consist of removing any lesion that may be causing the symptoms of the syndrome. If no lesion is present and the syndrome is not interfering with a person’s daily living, treatment may not be necessary.[548] 

Synonyms

• Progressive isolated segmental anhidrosis
• Unilateral loss of facial flushing and sweating with contralateral anhidrosis
• Sudden onset of unilateral flushing and sweating