Harlequin syndrome is an uncommon neurological condition that affects the autonomic nervous system, the part of your body that controls automatic functions like sweating and blood vessel dilation. This syndrome leads to a distinctive pattern of asymmetrical sweating and flushing on one side of the body, while the other side remains unaffected. It is considered a rare disorder. The name “Harlequin” comes from the Italian commedia dell’arte character, whose costume featured contrasting colors, reflecting the stark visual difference seen in the syndrome.
Symptoms and Manifestation
The defining characteristic of Harlequin syndrome is the sudden appearance of unilateral (one-sided) flushing and sweating. This typically affects the face, neck, and upper chest, though it can sometimes extend to the arms. The affected side becomes noticeably red and warm, often accompanied by profuse sweating, while the opposite side remains pale and dry, with a clear line of demarcation down the body’s midline.
This striking visual difference is often triggered by physical exertion, exposure to heat, or strong emotional responses. The symptoms can last anywhere from a few seconds to several minutes, or even hours, before the skin color and sweating patterns return to normal.
Underlying Causes and Common Triggers
Harlequin syndrome can stem from two main categories of causes: idiopathic, meaning the cause is unknown, or secondary, where it is linked to an identifiable underlying condition. Approximately half of all reported cases are idiopathic. In these idiopathic cases, the syndrome is generally benign and not associated with other health issues.
Secondary Harlequin syndrome occurs due to damage or disruption of the sympathetic nerve fibers that control sweating and blood vessel dilation on one side of the body. This nerve damage can result from various factors, including local trauma, benign tumors, or lesions that compress these nerve pathways. Certain medical procedures can also unintentionally affect these nerves, leading to symptoms. Other associated conditions include stroke, certain viral infections (such as human herpes virus-6 or varicella-zoster virus), and some autoimmune disorders.
Diagnosis and Medical Evaluation
The diagnosis of Harlequin syndrome relies on a clinical evaluation, assessing distinctive symptoms and patient history. This includes observing the characteristic asymmetrical sweating and flushing, often after a provoking factor like exercise or heat exposure. While the syndrome itself is usually benign, the medical evaluation is important to rule out any serious underlying conditions that could be causing the nerve dysfunction.
To exclude other potential causes, a doctor may recommend various diagnostic tests. These could include imaging studies like magnetic resonance imaging (MRI) or computed tomography (CT) scans of the brain, spinal cord, or other relevant areas to check for structural abnormalities or nerve compression. Specialized tests such as thermoregulatory sweat testing or quantitative sudomotor axon reflex testing (QSART) may also be performed to assess the function of the sympathetic nerves and evaluate sweating patterns.
Treatment and Prognosis
For many individuals with Harlequin syndrome, particularly the idiopathic form, treatment is not necessary as the condition is generally benign and symptoms often resolve. The temporary nature of the episodes means that daily life is typically not impaired. Reassurance and counseling from a healthcare provider can be helpful for those who experience anxiety or distress due to the sudden and noticeable appearance of symptoms.
However, if symptoms are persistent, significantly impact quality of life, or cause social embarrassment, treatment options are available. These might include medications such as anticholinergic drugs to reduce sweating or beta-blockers to manage flushing. Botulinum toxin (Botox) injections have also shown promise in reducing localized sweating. In rare, severe cases, surgical interventions like sympathectomy, which involves interrupting the affected nerve pathways, may be considered to achieve more balanced sweating and flushing. The long-term outlook for most people with Harlequin syndrome is favorable, especially when no underlying serious cause is identified.