Harlequin Syndrome: Causes, Symptoms and Treatment

It is a rare condition characterized by redness and sweating.

It occurs only on one side of the face and can happen for no apparent reason or response to warmth and exercise.

Harlequin syndrome is a result of damage to the autonomic nervous system. The “unconscious” part of the nervous system controls the organs’ involuntary muscular contractions, the gland’s activities, such as sweating and crying, and the fight or flight response.

The nerves carry instructions for these actions to different body parts, so damage to a single nerve can lose its functions.

Harlequin syndrome is an autonomic disorder that occurs at any age and is characterized by redness and unilateral sweating.

This affects the face and sometimes the arms and chest under thermal, exercise, or vigorous conditions without sympathetic ocular manifestations.

However, the tonic pupils, the parasympathetic oculomotor injury, and the supposed postganglionic or sympathetic deficits rarely occur.


A rare disorder that is often associated with profuse sweating and redness of the body.

Fortunately, the condition is not associated with severe complications and can be managed, although the result of the state is not good.

It is a relatively rare disorder that affects the autonomic nervous system.

The disorder is seen as extreme redness and sweat in the middle of the side of the body. The condition was unknown and remained anonymous until 1988, when it was observed in some patients.

The treatment is feasible only for a few patients. However, the disorder is not fatal.

Half of the body sweats profusely and reddens in the syndrome, while the other part does not sweat or redden. The symptoms appear involuntarily; one has no control over them, and occurs suddenly.

What causes harlequin syndrome?

The following are the common causal factors for the harlequin syndrome:

The traumatism or injury of the Sympathetic Nervous System (that part of the nervous system that responds to stress) can bring the symptoms of Harlequin syndrome.

It can be seen as a side effect of sympathetic endoscopic block or surgical intervention of unilateral endoscopic thoracic sympathectomy.

People who have tumors or have had a stroke may also experience the characteristics of Harlequin syndrome.

Usually, the face turns red and suddenly reddens, and there is profuse perspiration without any identifiable cause.

Occasionally, symptoms may appear when the person is exercising or is in hot conditions for too long.

What are the symptoms?

Harlequin syndrome is characterized by profuse sweating and blushing on one side of the body, usually the face, neck, and chest.

The other side of the body is normal and shows no blushing or sweating at all. The clinical characteristics of the syndrome occur involuntarily.

Symptoms vary from individual to individual but always include the “Harlequin sign,” where one side of the face does not sweat or redden, known as anhidrosis.

The effect is highly pronounced because the other half of the face compensates by sweating excessively – hyperhidrosis.


There is no specific treatment regimen for the condition. Surgical intervention is recommended in some instances. The doctor detects the altered nerve; then, the damage can be rectified.

In case the surgery is not feasible, a ganglionic block is performed. For ganglionic blockade, a local anesthetic is administered; It has been shown that this technique can reduce the duration and intensity of the symptoms of the harlequin syndrome.

Although this technique is relatively new, it effectively manages the disorder.

The outcome of a case of Harlequin syndrome is moderate to mild. The disorder causes discomfort and awkwardness, but it is not full of serious complications.

It is generally benign. It has been described in up to 10% of healthy newborns and is associated with a temporary imbalance in the tone of cutaneous blood vessels due to hypothalamic immaturity.

However, many different etiologies have been described, including dissection of the carotid artery, tumors, syringomyelia, multiple sclerosis, and iatrogenic effects of invasive procedures.

Recently, researchers have tried to find a pathogenic connection between migraine and the syndrome based on the autonomic dysfunction associated with migraine. However, this correlation has not yet been established.

The term “Harlequin syndrome” should be used exclusively for attacks of redness and sweating that are not associated with any other neurological symptoms.

When these symptoms appear along with other autonomic disorders, the term “harlequin sign” should be used.

The diagnostic process for patients should try to determine the organic cause.

If the symptoms are idiopathic, it is essential to assure patients that the disorder is benign and that follow-up examination will not be necessary.

Although idiopathic cases do not require treatment, contralateral sympathectomy can be performed when it has a severe psychological impact on patients.

However, this surgical procedure can lead to compensatory redness and sweating elsewhere.

The researchers postulate that compensatory neuronal activity on the healthy side accentuates skin symptoms typical of the disease. The dysfunction can be located in any of the three levels of the cervical sympathetic chain.

The first originates in the hypothalamus. It descends along the brainstem to the spinal cord, where it forms a synapse with the second neuron (preganglionic) of the intermediate column, at the level of segments C8-T2.

The preganglionic neuron leaves the spinal cord, travels through the ganglion, and ascends to the superior cervical ganglion through the paravertebral sympathetic chain, which is in contact with the apex of the lung.

The second (preganglionic) and third (postganglionic) neurons form a synapse in the upper cervical ganglion. Two branches leave this ganglion.

One runs along the internal carotid artery and includes the vasomotor and sudomotor fibers that innervate the nose and the medial frontal region and the sympathetic fibers that cause the iris to dilate.

The second branch extends along the external carotid artery and includes postganglionic vasomotor and sudomotor fibers that innervate the rest of the face.