Harlequin syndrome is a rare, clinically striking syndrome characterized by 
distinctly demarcated asymmetric facial flushing and sweating. It may be of 
idiopathic aetiology or caused by demonstrable ipsilateral damage to the 
sympathetic nervous system. A case is described where a patient presented to her 
general dental practitioner complaining of distinctly demarcated unilateral 
facial flushing and sweating. Onward referral resulted in a diagnosis of 
Harlequin syndrome. CPD/CLINICAL RELEVANCE: This article highlights the 
neurological signs and symptoms of Harlequin syndrome, making it easier to 
recognize if it presents in general dental practice.