Correction of hyperleucinemia in MSUD patients on leucine-free dietary therapy

Maple Syrup Urine Disease (MSUD) is a rare disorder of branched-chain amino acid catabolism associated with encephalopathy from accumulation of leucine. Leucine is closely monitored during normal growth and particularly during acute illness. As most hospitals do not have access to rapid plasma amino acid quantification, the initial management is often empirical. A model describing the reduction of plasma leucine in hyperleucinemic patients on leucine-free formula would help to guide management and optimize testing frequency.

We retrospectively reviewed charts from 15 MSUD patients comprising 29 episodes of hyperleucinemia that were managed with leucine-free formula. Episodes were categorized by clinical presentation.

Upon leucine restriction, plasma leucine concentrations fell exponentially at a rate proportional to approximately 50% of the starting value over each 24-hour period. Recovery appears to be sensitive to clinical status and triggering event of the hyperleucinemic episode. Patients with upper respiratory infections generally recovered slowly, while cases of dietary non-adherence resolved more quickly.

This general model may help anticipate leucine levels during clinical management of MSUD patients when using nutritional support and leucine-free formula. The response of individual patients may vary depending on clinical status and triggering factors.