PEPCK1 deficiency is a rare inborn error of metabolism disorder, characterized by the deficiency of the enzyme PEPCK1, one of the enzymes needed for gluconeogenesis, the process by which organisms produce sugars (namely glucose) from non-carbohydrate precursors (such as amino acids). In severe cases, symptoms may include persistent and very low levels of blood's sugar in newborns (neonatal hypoglycemia), failure to thrive, build-up of lactic acid in the blood (lactic acidosis), liver enlargement (hepatomegaly) and liver failure leading to neurological degeneration. Milder cases present during childhood with fewer and less serious liver problems. Infections and fasting may trigger the symptoms. PEPCK1 deficiency inheritance is autosomal recessive. It is caused by genetic changes in the PEPCK1 gene. PEPCK1 is the cytosolic form of the phosphoenolpyruvate carboxykinase (PEPCK) enzyme, the other being the mitochondrial (PEPCK2).