Pyruvate carboxylase (PC) deficiency is an inherited disorder that causes build-up of lactic acid in the blood, causing damage to the nervous system. This is due to a defective enzyme called pyruvate carboxylase. There are three types of PC deficiency. Type A has moderately severe symptoms beginning in infancy that include developmental delay, intellectual disability, slow growth, fatigue, muscle weakness, and difficulty breathing. Children with type A survive into early childhood. Type B has life-threatening symptoms that begin shortly after birth, including liver disease, low blood sugar, seizures and coma. Infants with type B will also have weak muscle tone and abnormal movements. They typically survive less than three months. Type C is a mild form that has minimal symptoms with normal to mildly delayed neurological development. A carefully managed diet and certain therapies have shown to ameliorate some symptoms but none have been able to improve neurological symptoms or prolong life expectancy. Pyruvate carboxylase deficiency is caused by pathogenic variants in the PC gene.