Although the syndrome is generally a benign condition with complete resolution if appropriate treatment is initiated, unilateral facial flushing can be a sign of several serious
[ncbi.nlm.nih.gov]
Harlequin syndrome is an extremely rare benign condition characterized by unilateral facial flushing and sweating.
[ncbi.nlm.nih.gov]
Harlequin's syndrome typically is considered to be an idiopathic, benign condition causing localized failure of the upper thoracic sympathetic chain, with sparing of the first
[nejm.org]