Harlequin syndrome associated with ganglioneuroblastoma-induced Horner syndrome

A 1-year-old boy presented with a 4-month history of hypertension, ptosis of the right upper eyelid, left hemifacial sweating, and flushing. He was diagnosed with Harlequin syndrome associated with Horner syndrome. Computed tomography revealed a mass lesion in the right superior mediastinum. Therefore, the patient underwent total tumor resection. Histological examination demonstrated ganglioneuroblastoma. The MYCN oncogene was not amplified, and the mitosis–karyorrhexis index was low. Accordingly, radiation and chemotherapy were not performed. No recurrence was observed within 8 months after surgery, and the patient’s blood pressure was normalized. However, the ptosis, hemifacial sweating, and flushing persisted.