An autosomal recessive fructose metabolism disorder due to absent or deficient fructose-1,6-diphosphatase activity. Gluconeogenesis is impaired, resulting in accumulation of gluconeogenic precursors (e.g., amino acids, lactate, ketones) and manifested as hypoglycemia, ketosis, and lactic acidosis. Episodes in the newborn infant are often lethal. Later episodes are often brought on by fasting and febrile infections. As patients age through early childhood, tolerance to fasting improves and development becomes normal.