Harlequin syndrome

Harlequin syndrome is a rare autonomic nervous system disorder characterized by unilateral flushing and sweating on one side of the face, with the contralateral side remaining pale and dry (anhidrotic), typically triggered by exercise, heat, or emotional stress. The condition results from a disruption of the sympathetic nervous system pathways that control facial sweating and blood vessel dilation. The affected (non-flushing) side of the face demonstrates impaired sympathetic innervation, making the normal flushing and sweating side appear abnormal by contrast. The characteristic 'harlequin' appearance — with a sharp midline demarcation between the red, sweating side and the pale, dry side — gives the syndrome its name. Harlequin syndrome primarily affects the autonomic nervous system, specifically the sympathetic fibers supplying the face. It can occur as an isolated (idiopathic) condition or may be associated with other autonomic disorders, brainstem lesions, superior mediastinal or cervical lesions, or iatrogenic causes such as surgery or epidural anesthesia. In some cases, it has been associated with Horner syndrome on the affected side, suggesting a preganglionic or postganglionic sympathetic lesion. The condition is generally considered benign when it occurs in isolation, though it can cause significant cosmetic and psychological distress. There is no specific curative treatment for Harlequin syndrome. Management is primarily supportive and focused on reassurance, as the condition is not life-threatening. In cases where an underlying cause is identified (such as a tumor or vascular lesion), treatment of the underlying condition may improve symptoms. Stellate ganglion block and contralateral sympathectomy have been reported in some cases, but evidence for these interventions remains limited. Patients should be evaluated for associated neurological conditions, particularly Horner syndrome and other autonomic neuropathies.

Common questions about Harlequin syndrome