Management of acute metabolic decompensation in maple syrup urine disease: guidance based on international clinical practice

Background Maple syrup urine disease (MSUD) is an autosomal recessive inborn error of metabolism caused by a deficiency of branched-chain ketoacid dehydrogenase, the enzyme involved in the second step of branched-chain amino acid catabolism. Of the three branched-chain amino acids (leucine, valine, and isoleucine), accumulation of leucine is the predominant factor causing acute metabolic decompensation in patients with MSUD. Main body In February 2025, eight expert physicians met to discuss the management of acute metabolic decompensation and propose recommendations after literature review (four guidelines and 20 other articles of interest). A practical clinical algorithm was established. Newborn screening was acknowledged to be a successful method of diagnosing MSUD at birth, facilitating early intervention to prospectively manage MSUD and reduce the frequency and severity of acute metabolic decompensation, although it was noted that infants with severe MSUD often present with acute metabolic decompensation before being diagnosed. The experts also identified several barriers to and gaps in the management of acute metabolic decompensation, and MSUD more generally, proposing potential actions to improve clinical outcomes. Acute metabolic decompensation requires prompt, effective treatment by a multidisciplinary team to ensure that circulating plasma leucine levels are rapidly reduced without causing complications (particularly cerebral edema). Where available, intravenous branched chain amino acid-free solutions (e.g., Maapliv, now approved in Europe) may represent an important treatment option. Adequate resources (treatments, laboratory services, dialysis units) are essential for effective management of acute metabolic decompensation. Liver transplantation is an accepted viable option for the long-term prevention of acute metabolic decompensation in eligible patients. Research is ongoing into new treatment options for MSUD, such as gene therapy. Conclusion Optimal management of acute metabolic decompensation in patients with MSUD requires prompt, effective treatment to reduce leucine levels without causing complications. A ready-to-use branched chain amino acid-free intravenous solution has been recently approved in Europe and research into new treatment options is ongoing.