Persistent Hyperinsulinemic Hypoglycemia with Pancreatic Teratoma in Infancy: A Case Report

BACKGROUND Pediatric intraabdominal pancreatic teratomas have been rarely reported. This is the first case of severe hyperinsulinemic hypoglycemia in a 6-month-old infant secondary to an intraabdominal teratoma. The hypoglycemia resolved after surgical removal. CASE REPORT A 6-month-old infant was seen in a pediatric emergency department with complaints of lethargy and abnormal eye movements. She was diagnosed with hyperinsulinemic hypoglycemia and started on diazoxide. A CT and MRI of the abdomen revealed a 165×77×72 mm cyst with a 51×45×30 mm solid structure connecting to the wall of the cyst by a stalk, raising suspicion of a fetus in fetu. The mass had no connection to her pancreas. Following total excision of the intraabdominal mass, her hypoglycemia resolved. Histopathological examination showed immature fetal pancreatic tissue consistent with a mature teratoma. Whole exon sequencing of the infant's peripheral blood showed a negative mutation of ABCC8 and presence of heterozygous variations of HNF1ß and IRS1 genes. CONCLUSIONS This is the first case report of an infant with severe hyperinsulinemic hypoglycemia secondary to a pancreatic teratoma. The heterozygous variations of HNF1ß and IRS1 genes likely played a role in the embryogenesis, causing a pancreatic teratoma and hyperinsulinemic hypoglycemia.