Abstract Background The Mauriac syndrome was described in 1930 as a peculiar combination of poorly controlled diabetes mellitus type 1, stunted growth and glycogenic hepatopathy. More recently, lactic acidosis was recognized as an additional feature, often induced by insulin treatment. Case presentation A 17-year old girl known for diabetes type 1A and Mauriac syndrome was admitted to the emergency room with hyperglycemia of > 41 mmol/l without ketoacidosis. Under a standard insulin regimen, hyperglycemia was rapidly corrected but marked hyperlactatemia occurred. Conclusions The mechanism of impaired glucose utilization and lactate elevation independent of ketoacidosis in Mauriac syndrome is intriguing. The rarity of Mauriac syndrome and its resemblance to glycogen storage diseases suggest the presence of a specific metabolic or genetic predisposition that remains to be identified.