IVD and systemic primary carnitine deficiency disease: Secondary carnitine deficiency due to a deficiency of 3-methylcrontonyl-CoA carboxylase or isovaleryl-CoA dehydrogenase (Table 1), which is involved in leucine metabolism, increases the excretion of carnitine via carnitine conjugation (e.g., 3-hydroxyisovalreylcarnitine) (Fig. 2).[6,13,51] Symptoms of secondary carnitine deficiency are mild, compared to primary carnitine deficiency.[1] The prevention and treatment of hypoglycemia is important in patients with defects in the fatty acid β-oxidation pathway, such as very long and medium chain acyl CoA dehydrogenase deficiency.