Introduction: Glycogen storage disease type I is a rare hereditary metabolic disorder, caused by a deficit of the glucose-6-phosphatase, an enzyme that catalyzes hydrolysis of glucose-6-phosphate to phosphate and glucose, inducing essentially hypoglycemia, hyperlactacidemia, hyperuricemia and hyperlipoproteinemia often at the expense of triglycerides. Hypertriglyceridemia is often moderate (<10 g / l) at the time of diagnosis, but in the long term, it can exceed 20g/l causing serious complications such as acute pancreatitis or hepatic adenoma. We report a case of glycogen storage disease type I revealed by major hypertriglyceridemia.Case report: A 10-month-old infant girl, with a family history of storage disease type I (brother), admitted to the pediatric department for recurrent seizures due to hypoglycemia evolving for 2 months, and hepatomegaly. The blood tests made on admission revealed a hepatic cytolysis with a liver enzyme level 5 times upper the limit of normal, a major hypertriglyceridemia at 10 g / l (<1.5 g / l), and a correct glycemia and uricaemia. The infant was put on an adequate diet therapy. The evolution was marked by good clinical improvement.Conclusion: Major hypertriglyceridemia is a metabolic abnormality often occurring during the course of glycogen storage disease type I, but sometimes it is discovered at the time of diagnosis requiring prompt management and strict monitoring to avoid complications.