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.