Maple Syrup Urine Disease (MSUD) is a rare disease, affecting an estimated 1 in 185,000 people worldwide.

While affecting any ethnicity, the disorder occurs much more frequently in certain ethnic groups, such as the Old Order Mennonite population with an estimated incidence of about 1 in 380 newborns, and the Ashkenazi Jewish population with an estimated incidence of 1 in 26,000 newborns.

MSUD is a rare metabolic disorder requiring lifelong restriction of branched-chain amino acids (BCAA), and targeted supplementation with valine (Val) and isoleucine (Ile) to maintain metabolic stability.

Specialized medical formulas provide all essential nutrients with the exception of the BCAA leucine, isoleucine, and valine. These amino acids must be added to the diet in the precise amounts needed for normal growth and development. A strict low protein diet and careful medical monitoring is essential throughout the lifespan.

Recommended plasma target range of Val and Ile concentrations is between 200 and 400 μmol/L (1)

If either Val or Ile fall below the treatment range, a suggested starting dose of 50-100 mg/day of Val or Ile should be given (2). The dose of either is then titrated according to their plasma levels. Inadequate supplementation could lead to metabolic decompensation, but the amounts required are variable and depend on natural Leu tolerance and plasma concentrations.

Inpatient Therapy

Inpatient management of MSUD requires a more intensive approach than outpatient care. Daily supplementation with isoleucine and valine is recommended at doses between 20 mg and 120 mg per kilogram of body weight. These supplements should be adjusted as needed to maintain steady plasma levels of 400–800 mmol/L for each amino acid. (2)

See the Valine and Isoleucine product information for dosage and administration guidance, or find out about the MSUD Patient Registry.

(1) Nutrition management guideline for maple syrup urine disease: An evidence- and consensus-based approach – ScienceDirect
(2) Maple Syrup Urine Disease – StatPearls – NCBI Bookshelf