Feeling flush?
Harlequin sign might sound like a fun card game or Halloween outfit — but it’s actually a rare nervous system condition characterized by asymmetrical sweating.
Sydney Patrice, 26, a physical therapist from Baltimore, shared a video on TikTok in which she explained that only half her face turns red and sweaty during exercise — while the other side stays ghostly pale and completely dry.
“One of the nerves got messed up in one of my neck surgeries last year,” she said.
“And so now, whenever I go running, only half my face gets red.”
Neurosurgeon Dr. Betsy Grunch chimed in online to share how something like this can happen.
“There are two syndromes that could potentially happen after damage to your autonomic nervous system,” she said.
“If you’re stressed out, your eyes get really big, your face gets flushed, you sweat, you get dry mouth — that’s all part of our body’s fight or flight mechanism and it travels through the sympathetic chain, which lies in front of the spine.”
When that chain gets damaged, it can cause two conditions: Horner syndrome and Harlequin syndrome.
Horner syndrome is characterized by drooping eyelids, constricted pupils and a lack of sweating on one side of the face.
Meanwhile, Harlequin syndrome causes only one side of the face to get flushed and sweaty, while the other remains completely dry.
Why only one side?
“Because you have a sympathetic chain on either side and each supplies one side of your face,” Grunch noted.
“So if it’s damaged on one side, it will affect that one side.”
While it is a known risk with anterior cervical surgery — where doctors operate on the part of your spine that’s in your neck by accessing it through the front — it’s extremely rare.
Though exact numbers are difficult to pin down, Harlequin syndrome is estimated to affect fewer than 1,000 people in the US, according to the Cleveland Clinic.
It was first described in medical literature in 1988.
Harlequin syndrome is generally a temporary and benign condition, but symptoms can become permanent in some situations, according to Grunch.
While extraordinary, it is possible to have Horner syndrome and Harlequin syndrome — as Sydney appears to — since both involve injury to the sympathetic chain.
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