pyruvate carboxylase deficiency, severe neonatal type (MONDO_0018142) can be described as follows. Severe neonatal pyruvate carboxylase (PC) deficiency (Type B) is a rare, extremely severe form of PC deficiency characterized by severe, early-onset metabolic acidosis, and a generally fatal outcome in early infancy. Also known as: pyruvate carboxylase deficiency type B.