Natural history of children and adults with maple syrup urine disease in the NBS-MSUD Connect registry

Comprehensive Iranian guidelines for the diagnosis and management of maple syrup urine disease: an evidence- and consensus- based approach

Maple Syrup Urine Disease (MSUD) disease is a defect in the function of the Branched-chain 2-ketoacid dehydrogenase complex (BCKDH). It is caused by pathogenic biallelic variants in BCKDHA, BCKA decarboxylase, or dihydrolipoamide dehydrogenase. The brain is the major organ involved in MSUD. MSUD happens in about 1 in 86,800 to 185,000 live births. According to some diversity in the management of Iranian patients with MSUD, the development of a national guideline is essential. This guideline is provided through a literature search on articles in PubMed, Scopus, Web of Sciences, Cochrane, and Embase databases from 2001 to 2022 accompanied by a consensus of physicians of different centers in Iran who are experts in the diagnosis and management of this disease. This article considers pathogenesis, epidemiology, clinical manifestations, diagnosis, treatment, and monitoring of MSUD patients with limited recourse.

Current status and future directions of liver transplantation for metabolic liver disease in children

Orthotopic liver transplantation (OLT) in the care of children with inborn errors of metabolism (IEM) is well established and represent the second most common indication for pediatric liver transplantation in most centers worldwide, behind biliary atresia. OLT offers cure of disease when a metabolic defect is confined to the liver, but may still be transformative on a patient's quality of life reducing the chance of metabolic crises causing neurological damage in children be with extrahepatic involvement and no "functional cure." Outcomes post-OLT for inborn errors of metabolism are generally excellent. However, this benefit must be balanced with consideration of a composite risk of morbidity, and commitment to a lifetime of post-transplant chronic disease management. An increasing number of transplant referrals for children with IEM has contributed to strain on graft access in many parts of the world. Pragmatic evaluation of IEM referrals is essential, particularly pertinent in cases where progression of extra-hepatic disease is anticipated, with long-term outcome expected to be poor. Decision to proceed with liver transplantation is highly individualized based on the child's dynamic risk-benefit profile, their family unit, and their treating multidisciplinary team. Also to be considered is the chance of future treatments, such as gene therapies, emerging in the medium term.

Leucine tolerance in children with MSUD is not correlated with plasma leucine levels at diagnosis

OBJECTIVES

Maple syrup urine disease (MSUD) is an inborn metabolic disease. The nutritional treatment with restricted intake of branched chain amino acids and prevention of leucine toxicity are crucially important for a favorable outcome. The aim of this study is to analyze the relation of blood leucine levels at diagnosis with future leucine tolerances, to determine whether any prediction about the future leucine tolerances or plasma leucine levels is possible by evaluating blood leucine levels at diagnosis.

METHODS

The study group consisted of 45 MSUD patients. Leucine levels at diagnosis were compared with age at diagnosis, leucine tolerances, maximum leucine levels/ages, and average blood leucine levels.

RESULTS

The mean plasma leucine level at diagnosis was 2,355.47 ± 1,251.7 μmol/L (ref: 55-164 μmol/L). The median age at diagnosis was 17 days. Leucine tolerances per kg body weight declined until the age of 8 years and stabilized subsequently. The average age of maximum leucine level during follow-up was 3.14 ± 1.92 years, and the mean maximum lifetime plasma leucine level on follow-up was 1,452.13 ± 621.38 μmol/L. The leucine levels at diagnosis did not have any significant relationship with lifetime leucine tolerances, maximum plasma leucine levels or mean plasma leucine levels.

CONCLUSIONS

The plasma leucine levels at diagnosis did not have a predictive value for later leucine tolerances or plasma leucine levels. The maximum lifetime leucine level is likely to happen within the first 3 years of life, underlining the importance of good metabolic control and compliance to dietary treatment at early ages.

Domino liver transplants: where do we stand after a quarter-century? A US national analysis

BACKGROUND

Domino liver transplantation (DLT) utilizes a phenotypically normal explant from select recipients as a donor graft in another patient. The procedure is not widely employed and remains restricted to a small number of centers. The purpose of this study was to assess the national profile of DLT in the United States (US) and evaluate current survival outcomes.

METHODS

The United Network for Organ Sharing (UNOS) database was queried for all liver transplants (LT) between 1996 and 2020. Outcomes of interest were long-term graft and patient survival.

RESULTS

Of 181,976 LTs performed nationally during the study period, 185 (0.1%) were DLTs. Amyloidosis and maple syrup urine disease (MSUD) accounted for 83% of dominoed allografts. Out of 210 explants with amyloidosis, 103 (49%) were dominoed into secondary recipients. Only 50 (22%) of all MSUD explants (n = 227) were dominoed. Graft survival was 79%, 73% and 53% at 3-, 5- and 10-years, respectively, for DLT recipients. Overall patient survival was 83%, 76% and 57% at 3-, 5- and 10-years.

CONCLUSION

Despite excellent long-term survival outcomes, DLT allografts comprise a very small percentage of the liver donor pool. A large proportion of potential DLTs may be unconscionably excluded despite shortages in deceased donor organs.

Brain Branched-Chain Amino Acids in Maple Syrup Urine Disease: Implications for Neurological Disorders

Maple syrup urine disease (MSUD) is an autosomal recessive disorder caused by decreased activity of the branched-chain α-ketoacid dehydrogenase complex (BCKDC), which catalyzes the irreversible catabolism of branched-chain amino acids (BCAAs). Current management of this BCAA dyshomeostasis consists of dietary restriction of BCAAs and liver transplantation, which aims to partially restore functional BCKDC activity in the periphery. These treatments improve the circulating levels of BCAAs and significantly increase survival rates in MSUD patients. However, significant cognitive and psychiatric morbidities remain. Specifically, patients are at a higher lifetime risk for cognitive impairments, mood and anxiety disorders (depression, anxiety, and panic disorder), and attention deficit disorder. Recent literature suggests that the neurological sequelae may be due to the brain-specific roles of BCAAs. This review will focus on the derangements of BCAAs observed in the brain of MSUD patients and will explore the potential mechanisms driving neurologic dysfunction. Finally, we will discuss recent evidence that implicates the relevance of BCAA metabolism in other neurological disorders. An understanding of the role of BCAAs in the central nervous system may facilitate future identification of novel therapeutic approaches in MSUD and a broad range of neurological disorders.