Patients with type I glycogen storage disease (GSD) have poor tolerance to fasting, sometimes less than 3 hours during infancy. Even though most patients are able, as they get older, to tolerate a longer fasting period, they are at permanent risk for fast-induced hypoglycaemia, even in adulthood. Klüver Bucy syndrome, is characterized by psychic blindness (inability to recognize familiar objects), hypermetamorphosis (strong tendency to react to visual stimulus), increased oral exploration, placidity, indiscriminate hyper-sexuality and change in dietary habits. In this case report, we describe the development of Klüver Bucy syndrome in a 28-year-old man with type Ib GSD, following prolonged and severe hypoglycaemia triggered by a common respiratory infection.