RESUMEN
Background: Paraneoplastic syndromes often cause endocrine, neurological, cutaneous, and hematologic pathologies, and cases with digestive symptoms as prominent cases are rare. Case Description: A 1-year-old child admitted to the emergency department with severe abdominal distension was later diagnosed with sacrococcygeal yolk cystoma with ulcerative colitis. After symptomatic management, surgical removal of the tumor, and JEB chemotherapy, the symptoms of ulcerative colitis disappeared completely. After 7 years of follow-up, the child grew and developed well, and there was no recurrence of tumor and ulcerative colitis. Conclusion: Yolk sac tumor with ulcerative colitis is a rare paraneoplastic syndrome with complex clinical manifestations.