BlueCross BlueShield of Tennessee Medical Policy Manual

Nutritional Treatment of Inborn Errors of Metabolism


Inborn errors of metabolism are congenital disorders characterized by deficiencies or defects in vital enzymes that are needed to facilitate normal metabolism.  Although these disorders are rare, the four most commonly diagnosed disorders are phenylketonuria (PKU), maple-syrup urine disease (MSUD), tyrosinemia and homocystinuria.  All are treated with a restricted diet designed to avoid certain proteins or amino acids. 

If these disorders are left untreated, the individual (mostly infants or young children) will sustain severe health complications or die. Only a qualified physician and a clinical nutritionist familiar with inborn errors of metabolism should monitor this treatment process. This nutritional treatment may include specially formulated products based on appropriate medical evaluation and/or nutritional prescription products that can only be obtained from specialized vendors and pharmacies.





American Academy of Pediatrics Committee on Nutrition. (1994). Reimbursement for medical foods for inborn errors of metabolism. Retrieved November 9, 2018 from

Camp, K., Lloyd-Puryear, M. & Huntington, K. (2012).Nutritional treatment for inborn errors of metabolism: indications, regulations, and availability of medical foods and dietary supplements using Phenylketonuria as an example. Molecular Genetics & Metabolism, 107 (1-2), 3-9. (Level 5 evidence)

Frazier, D. M., Allgeier, C., Homer, C., Marriage, B. J., Ogata, B., Rohr, F., et al. (2014). Nutrition management guideline for maple syrup urine disease: an evidence- and consensus-based approach. Molecular Genetics and Metabolism, 112 (3), 210-217. (Level 1 evidence)

Ney, D., Stroup, B., Clayton, M., Murali, S., Rice, G., Rohr, F., & Levy, H. (2016). Glycomacropeptide for nutritional management of phenylketonuria: a randomized, controlled, crossover trial. The American Journal of Clinical Nutrition, 104, 334-345. (Level 2 evidence)

Southeast Regional Genetics Network. Management Guidelines Portal. (2013, February; updated 2016, August). Retrieved November 9, 2018 from

Tennessee Code: Title 56 Insurance: Chapter 7 Policies and Policyholders: Part 25 Mandated Insurer or Plan Options: 56-7-2505. Phenylketonuria (PKU) treatment. Retrieved November 9, 2018 from




Policies included in the Medical Policy Manual are not intended to certify coverage availability. They are medical determinations about a particular technology, service, drug, etc. While a policy or technology may be medically necessary, it could be excluded in a member's benefit plan. Please check with the appropriate claims department to determine if the service in question is a covered service under a particular benefit plan. Use of the Medical Policy Manual is not intended to replace independent medical judgment for treatment of individuals. The content on this Web site is not intended to be a substitute for professional medical advice in any way. Always seek the advice of your physician or other qualified health care provider if you have questions regarding a medical condition or treatment.

This document has been classified as public information.