Introduction and background - MSUD

Maple Syrup Urine Disease (MSUD) is an inborn error of metabolism, caused by branched-chain α-ketoacid dehydrogenase deficiency (BCKD). This results in the accumulation of high concentrations of the branched chain amino acids (BCAA), leucine (LEU), isoleucine (ILE) and valine (VAL) and their corresponding α-ketoacids. Exogenous BCAAs from dietary protein intake are precursors for protein synthesis. BCAAs are also used as alternative energy source when consumed in excess of anabolic needs or during endogenous muscle protein catabolism. Clinical severity can range from asymptomatic findings and in some life-threatening episodes with multi organ involvement in others^1,2

The main principle in the dietary management of amino acid disorders is to limit intake of the affected amino acids, while preventing catabolism.

In MSUD this translates in the need to rapidly reduce toxic metabolites by a restriction of dietary BCAA intake, which will allow BCAA amino acid concentrations to stay within the target plasma ranges and reduce catabolism along with optimal nutritional supply to promote anabolism and optimal growth. Emergency management is a key part of dietary management, aiming for promotion of anabolism, including a high energy diet, transient lowering of natural protein intake.^4,5

MSUD has an estimated incidence of approximately 1 in 185.000. In some populations, like the Mennonite populations in the US, MSUD has a much higher frequency up to 1 in 176³.

Early diagnosis of MSUD through new born screening in the first days of life is now established in most Western countries in the world. If immediate initiation of appropriate dietary intervention consequently is initiated, it will prevent children with MSUD demonstrating these severe clinical manifestations like metabolic intoxication and encephalopathy.

Nutricia supports ‘diet for life’ for all patients with MSUD. Research has shown that adherence to a well-managed diet plan has the best possible clinical outcomes for patients with MSUD.

References

Knerr I, Vockley J, Gibson KM. Disorders of leucine, isoleucine and valine metabolism. In; Blau N (ed) Physician’s guide to the diagnosis, treatment and follow-up of inherited metabolic diseases, 2^nd edn. Springer Heidelberg, 2014103-142
Frazier DM, Allgeier C et al. Nutrition management guideline for maple syrup disease: An evidence-and consensus-based approach. Molecular Genetic and Metabolism. 2014:112.
Strauss KA, Puffenberger EG, and Morton DH. 1993, Last update 2009. Maple Syrup Urine Disease.
Dixon MD, MacDonald A, White F, Stafford J. Disorders of Amino Acid Metabolism, Organic Acidemias and Urea Cycle disorders. In: Clinical Paediatric Dietetics. 4^th ed: West Sussex: John Wiley & Sons Limited, 2014:381-525.
GMDI: Nutrition Management guidelines for MSUD. https://southeastgenetics.org/ngp/guidelines.php

The products mentioned within the material are classified as Foods for Special Medical Purposes (FSMPs), intended for patients who have been medically diagnosed and must be under medical supervision.