Unilateral facial flushing and anhidrosis: a case of idiopathic Harlequin syndrome with successful botulinum toxin treatment.

Dear Editor, Harlequin syndrome is a rare autonomic disorder characterized by unilateral facial flushing and sweating caused by dysfunction of sympathetic innervation. Although generally considered a benign condition, it may occasionally represent the first manifestation of underlying neurological or structural abnormalities, including brainstem lesions, multiple sclerosis, or thoracic spinal cord disorders. Due to its striking clinical appearance, Harlequin syndrome may be misinterpreted as an allergic reaction, chronic urticaria, or other dermatological conditions, potentially delaying diagnosis. We report a case of idiopathic Harlequin syndrome in a middle-aged woman, highlighting the importance of recognizing this uncommon autonomic disorder in dermatological practice. [...].