Intellectual performance of children with maple syrup urine disease

The oral phenotype and dental management in patients with maple syrup urine disease; case report and scoping review

BACKGROUND AND OBJECTIVES

The literature about oral manifestations and dental management in maple syrup urine disease (MSUD) is sparse. The aim of this report is to present a new case of MSUD with special emphasis on oral findings and to review the relevant literature.

METHOD

A case report of a 4-year-old boy with MSUD was described according to the CARE guidelines for describing case reports. Scoping review of relevant literature was performed, according to the PRISMA-ScR guidelines, by searching PubMed, Medline, Embase, and the grey literature for articles describing dental management and/or oral manifestations in MSUD.

RESULTS

The initial search identified 219 articles, but only 4 met the inclusion criteria. Rampant caries and plaque induced gingivitis were the main oro-dental findings in MSUD. Other oral findings included enamel hypoplasia, skeletal abnormalities, and abnormal oral behaviors. Disease-related factors appeared to play a major role in the development of the observed oral phenotype.

CONCLUSION

Oral health in MSUD seems to be influenced by the reliance on semi-synthetic diet and associated neurocognitive complications. Tailored oral health promotional interventions should be included in the multidisciplinary management of patients with MSUD.

Oral health status of children and young adults with maple syrup urine disease in Turkey

Background

Maple syrup urine disease (MSUD) is an inherited disorder clinically characterized by ketoacidosis, seizures, coma, psychomotor delay, and intellectual disability. The treatment requires a life-long protein-restricted diet, rich in carbohydrates and fats, supplemented with a medical amino acid formula. Diet, oral health and general health influence each other in a vicious cycle. The aim of this study was to investigate the oral health status of children and young adults with MSUD in Turkey.

Methods

A descriptive study was conducted on patients with MSUD who applied for routine follow-up to the pediatric metabolic diseases clinic at Hacettepe University, Children's Hospital in Ankara, Turkey in a 12-month period. Patients with any other concomitant genetic diseases and acute infection were excluded. A total of twenty-five patients were enrolled and underwent oral examination including DMFT/S, dmft/s (decayed/missing/filled teeth/surfaces for deciduous and primary teeth, respectively), plaque and gingival indices. Panoramic radiographs were obtained in 12 cooperative patients.

Results

Mean age was 9.88 ± 5.68 s.d years. More than half of the parents had only primary school level education, and low income. Fourteen patients consumed medical formula during or right before sleep. Fourteen patients reported caries-associated pain. Gingival inflammation was present in all 15 patients who cooperated for evaluation. Seven out of twelve patients had at least one dental anomaly or alterations in mandibular morphology. Five patients had previously been treated for caries under general anesthesia. To our knowledge, this is the first study to document oral clinical and radiologic findings in patients with MSUD.

Conclusions

Impaired oral health was observed in this rare disease population. Regular dental referral by physicians, preventive measures and dental treatments should be included in multidisciplinary management of maple syrup urine disease to promote oral health.

Continuous venovenous hemodiafiltration in the treatment of newborns with an inborn metabolic disease: a single center experience

Background/aim

Most inborn metabolic diseases are diagnosed during the neonatal period. The accumulation of toxic metabolites may cause acute metabolic crisis with long-term neurological dysfunction and death. Renal replacement therapy (RRT) modalities allow the efficient removal of toxic metabolites. In this study, we reviewed our experience with continuous venovenous hemodiafiltration (CVVHDF) as RRT for newborns with an inborn metabolic disease.

Materials and methods

Patients diagnosed with an inborn metabolic disease and who received CVVHDF treatment at our neonatal intensive care unit between January 2014 and December 2017 were included in this study. Their demographic and clinical data were collected, and the efficacy and safety of CVVHDF was evaluated.

Results

A total of nine continuous RRT (CRRT) sessions as CVVHDF were performed in eight newborns with a diagnosis of urea cycle defect (n = 5), maple syrup urine disease (n = 2), or methylmalonic acidemia (n = 1). The mean age at admission was 10 ± 8.6 days (range: 3–28 days). The mean plasma levels of ammonium were 1120 ± 512.6 mg/dL and 227.5 ± 141.6 mg/dL before and at the end of the treatment, respectively. Plasma levels of leucine were 2053.5 ± 1282 µmol/L and 473.5 ± 7.8 µmol/L before and at the end of the treatment, respectively. The CVVHDF duration was 32.3 ± 11.1 h (median: 37 h; range: 16–44 h), and the mean length of hospitalization was 14.6 ± 12.9 days. The mean duration of CVVHDF was 32.3 ± 11.1 h (range: 16–44 h). Circuit clotting was the most common observed complication (37.5%) and the survival rate was 50%. Among surviving patients, two developed severe and two developed mild mental and motor retardation.

Conclusion

CVVHDF is a CRRT modality that can be used to treat newborns with an inborn metabolic disease. Early diagnosis, commencement of specific medical therapy, diet, and extracorporeal support, if needed, are likely to result in improved short and long-term outcomes.

Surgical Aspects of Liver Transplantation and Domino Liver Transplantation in Maple Syrup Urine Disease: Analysis of 15 Donor-Recipient Pairs

Liver transplantation (LT) has been shown to be a feasible treatment in patients with severe forms of maple syrup urine disease (MSUD). Because of a sufficient extrahepatic enzyme activity in non-MSUD individuals, the organ of MSUD patients can be used as a domino graft. We performed a retrospective data collection of all LTs for MSUD carried out at the University Medical Center Hamburg-Eppendorf (2016-2018). Moreover, data from all consecutive domino LTs of the MSUD grafts either transplanted at our institution or allocated to other transplant centers were analyzed. During the study period, 15 LTs in MSUD patients were performed (12 children, 3 adults; median age, 10.9 years; range, 0.3-26.1 years). Biliary complications occurred in 20%, and 13.3% suffered from bleeding complications. No further surgical problems occurred. At present, all MSUD patients are alive with a well-functioning liver graft and on an unrestricted diet. In total, 14 consecutive domino LTs were performed. No surgical complications requiring intervention occurred. One patient died because of HCC relapse, and all other patients are alive with good liver graft function. In conclusion, the use of MSUD livers as domino grafts is safe and allows application of LT in MSUD patients without net extraction of a liver graft from the limited donor pool.

Long-term metabolic follow-up and clinical outcome of 35 patients with maple syrup urine disease

BACKGROUND

Maple syrup urine disease (MSUD) is a rare disease that requires a protein-restricted diet for successful management. Little is known, however, about the psychosocial outcome of MSUD patients. This study investigates the relationship between metabolic and clinical parameters and psychosocial outcomes in a cohort of patients with neonatal-onset MSUD.

METHODS

Data on academic achievement, psychological care, family involvement, and biochemical parameters were collected from the medical records of neonatal MSUD patients treated at Necker Hospital (Paris) between 1964 and 2013.

RESULTS

Thirty-five MSUD patients with a mean age of 16.3 (2.1-49.0) years participated. Metabolic decompensations (plasma leucine >380 μmol/L) were more frequent during the first year of life and after 15 years, mainly due to infection and dietary noncompliance, respectively. Leucine levels increased significantly in adulthood: 61.5% of adults were independent and achieved adequate social and professional integration; 56% needed occasional or sustained psychological or psychiatric care (8/19, with externalizing, mood, emotional, and anxiety disorders being the most common). Patients needing psychiatric care were significantly older [mean and standard deviation (SD) 22.6 (7.7) years] than patients needing only psychological follow-up [mean (SD) 14.3 (8.9) years]. Patients with psychological follow-up experienced the highest lifetime number of decompensations; 45% of families had difficulty coping with the chronic disease. Parental involvement was negatively associated with the number of lifetime decompensations.

CONCLUSION

Adults had increased levels of plasma leucine, consistent with greater chronic toxicity. Psychological care was associated with age and number of decompensations. In addition, parental involvement appeared to be crucial in the management of MSUD patients.

The first case of domino-split-liver transplantation in maple syrup urine disease

The enzymatic defect in MSUD results in accumulation of neurotoxic metabolites of BCAAs. LTX has shown to be a feasible strategy in patients non-responsive to diet. Because of sufficient enzyme activity in extrahepatic tissues in healthy people, the MSUD liver graft is a suitable domino organ. We present the first case of a technical challenging ex situ split of a MSUD domino organ transplanted into two pediatric recipients. The domino graft donor was a 21-year-old female (58 kg) suffering from MSUD with recurrent metabolic decompensation despite strict diet. The organ was allocated to a 14-year-old girl (55 kg) with primary sclerosing cholangitis. Due to excellent organ quality and suitable anatomy, a backward split for a girl of 3 months (5 kg) with decompensated liver cirrhosis due to biliary atresia was performed. The postoperative course was without relevant complications, and the three recipients were discharged on postoperative days 28, 29, and 45, respectively, with good organ function. BCAAs in plasma were normal in the two domino graft recipients, and the MSUD patient showed mildly elevated but stable BCAA concentrations despite an unrestricted diet. Split-domino LTX enabled successful transplantation of three patients of the waiting list with only one deceased donor graft.

Neurocognitive profiles in MSUD school-age patients

Maple syrup urine disease (MSUD), an inborn error of amino acids catabolism is characterized by accumulation of branched chain amino acids (BCAAs) leucine, isoleucine, valine and their corresponding alpha-ketoacids. Impact on the cognitive development has been reported historically, with developmental delays of varying degree. Currently, earlier diagnosis and improved management allow a better neurodevelopment, without requirement of special education. However, specific impairments can be observed, and so far, results of detailed neurocognitive assessments are not available. The aim of this study was to analyse neurocognitive profiles of French MSUD patients. This was a multicentre retrospective study on MSUD patients who underwent neurocognitive evaluation at primary school age. Twenty-one patients with classical neonatal onset MSUD were included. The patients' mean age at the time of evaluation was 8.7 years. The mean intellectual quotient (IQ) score was in the normal range (95.1 ± 12.6). In a subset of eight patients, a consistent developmental pattern of higher verbal than performance IQ was observed (mean of the difference 25.7 ± 8.7, p < 0.0001). No correlation could be established between this pattern and long-term metabolic balance (BCAA blood levels), or severity of acute metabolic imbalances, or leucine blood levels at diagnosis and time to toxin removal procedure. These data show that some MSUD patients may exhibit an abnormal neurocognitive profile with higher verbal than performance abilities. This might suggest an executive dysfunction disorder that would need to be further investigated by specialized testing. This pattern is important to detect in MSUD, as appropriate neuropsychological treatment strategies should be proposed.

Maple Syrup Urine Disease Complicated with Kyphoscoliosis and Myelopathy

Maple syrup urine disease (MSUD) is an autosomal recessive aminoacidopathy secondary to an enzyme defect in the catabolic pathway of the branched-chain amino acids (BCAAs: leucine, isoleucine, and valine). Accumulation of their corresponding keto-acids leads to encephalopathy if not treated in time. A newborn male patient was suspected to have MSUD after tandem mass study when he presented symptoms and signs suggestive neonatal sepsis, anemia, and diarrhea. Food restriction of BCAAs was started; however, acrodermatitis enteropathica-like skin eruptions occurred at age 2 months. The skin rashes resolved after adding BCAAs and adjusting the infant formula. At age 7 months, he suffered from recurrent skin lesions, zinc deficiency, osteoporosis, and kyphosis of the thoracic spine with acute angulation over the T11-T12 level associated with spinal compression and myelopathy. After supplementation of zinc products and pamidronate, skin lesions and osteopenia improved gradually. Direct sequencing of the DBT gene showed a compound heterozygous mutation [4.7 kb deletion and c.650-651insT (L217F or L217fsX223)]. It is unusual that neurodegeneration still developed in this patient despite diet restriction. Additionally, brain and spinal magnetic resonance imaging, bone mineral density study, and monitoring of zinc status are suggested in MSUD patients.

Old treatments for new insights and strategies: proposed management in adults and children with alkaptonuria

Alkaptonuria (AKU) is caused by deficiency of the enzyme homogentisate 1,2 dioxygenase. It results in an accumulation of homogentisate which oxidizes spontaneously to benzoquinone acetate, a highly oxidant compound, which polymerises to a melanin-like structure, in a process called ochronosis. Asymptomatic during childhood, this accumulation will lead from the second decade of life to a progressive and severe spondylo-arthopathy, associated with multisystem involvement: osteoporosis/fractures, stones (renal, prostatic, gall bladder, salivary glands), ruptures of tendons/muscle/ligaments, renal failure and aortic valve disease. The pathophysiological mechanisms of AKU remain poorly understood, but recent advances lead us to reconsider the treatment strategy in AKU patients. Besides the supporting therapies (pain killers, anti-inflammatory drugs, physiotherapy, joints replacements and others), specific therapies have been considered (anti-oxidant, low protein diet, nitisinone), but clinical studies have failed to prove efficiency on the rheumatological lesions of the disease. Here we propose a treatment strategy for children and adults with AKU, based on a review of the latest findings on AKU and lessons from other aminoacipathies, especially tyrosinemias.

Inherited Metabolic Disorders: Aspects of Chronic Nutrition Management

The introduction of newborn screening and the development of new therapies have led to an expanding population of patients with inherited metabolic disorders, and these patients are now entering adulthood. Dietary therapy is the mainstay of treatment for many of these disorders, and thus, trained metabolic dietitians are critical members of the multidisciplinary team required for management of such patients. The main goals of dietary therapy in inborn errors of metabolism are the maintenance of normal growth and development while limiting offending metabolites and providing deficient products. Typically, the offending metabolite is either significantly reduced or removed completely from the diet and then reintroduced in small quantities until blood levels are within the normal range. Such treatment is required in infancy, childhood, and adulthood and requires careful monitoring of micronutrient and macronutrient intake throughout the life span. The goal of this review is to highlight the basic principles of chronic nutrition management of the inborn errors of protein, carbohydrate, and fat metabolism.

Nutrition management guideline for maple syrup urine disease: an evidence- and consensus-based approach

In an effort to increase harmonization of care and enable outcome studies, the Genetic Metabolic Dietitians International (GMDI) and the Southeast Regional Newborn Screening and Genetics Collaborative (SERC) are partnering to develop nutrition management guidelines for inherited metabolic disorders (IMD) using a model combining both evidence- and consensus-based methodology. The first guideline to be completed is for maple syrup urine disease (MSUD). This report describes the methodology used in its development: formulation of five research questions; review, critical appraisal and abstraction of peer-reviewed studies and unpublished practice literature; and expert input through Delphi surveys and a nominal group process. This report includes the summary statements for each research question and the nutrition management recommendations they generated. Each recommendation is followed by a standardized rating based on the strength of the evidence and consensus used. The application of technology to build the infrastructure for this project allowed transparency during development of this guideline and will be a foundation for future guidelines. Online open access of the full, published guideline allows utilization by health care providers, researchers, and collaborators who advise, advocate and care for individuals with MSUD and their families. There will be future updates as warranted by developments in research and clinical practice.

Utility of peritoneal dialysis in neonates affected by inborn errors of metabolism

AIM

Some inborn errors of metabolism induce metabolic encephalopathy through accumulation of neurotoxic metabolites. Rapid elimination of these metabolites by peritoneal or extracorporeal dialysis is crucial to prevent neuronal damage or death. In this retrospective study, we evaluated the outcomes of nine neonates with metabolic crisis treated with peritoneal dialysis.

METHOD

Six neonates with hyperammonemic coma (four with organic acidemias, two with urea cycle disorders) and three with leucine accumulation due to maple syrup urine disease (MSUD) were managed with peritoneal dialysis in conjunction with dietary and pharmacological therapy.

RESULTS

Three patients with organic acidemia survived. One of the patients was normal; others had moderate and severe neurological impairments. One neonate with organic acidemia and both neonates with urea cycle disorders died. Two of the three patients with MSUD survived without neurological impairment; the other had severe neurological damage and died at 9 months of age due to sepsis.

CONCLUSION

Theoretically, extracorporeal dialysis should be the first dialysis treatment of choice; however, this report demonstrates that peritoneal dialysis has a chance to prevent neurological damage in some patients. Therefore, in developing countries without extracorporeal dialysis opportunities, it can be still a life-saving procedure, if it is applied with skilled staff and standard procedures.

Branched-chain amino acid metabolism: from rare Mendelian diseases to more common disorders

Branched-chain amino acid (BCAA) metabolism plays a central role in the pathophysiology of both rare inborn errors of metabolism and the more common multifactorial diseases. Although deficiency of the branched-chain ketoacid dehydrogenase (BCKDC) and associated elevations in the BCAAs and their ketoacids have been recognized as the cause of maple syrup urine disease (MSUD) for decades, treatment options for this disorder have been limited to dietary interventions. In recent years, the discovery of improved leucine tolerance after liver transplantation has resulted in a new therapeutic strategy for this disorder. Likewise, targeting the regulation of the BCKDC activity may be an alternative potential treatment strategy for MSUD. The regulation of the BCKDC by the branched-chain ketoacid dehydrogenase kinase has also been implicated in a new inborn error of metabolism characterized by autism, intellectual disability and seizures. Finally, there is a growing body of literature implicating BCAA metabolism in more common disorders such as the metabolic syndrome, cancer and hepatic disease. This review surveys the knowledge acquired on the topic over the past 50 years and focuses on recent developments in the field of BCAA metabolism.

Efficacy and safety of intermittent hemodialysis in infants and young children with inborn errors of metabolism

BACKGROUND

Intermittent hemodialysis (IHD) is the most efficient form of renal replacement therapy (RRT) for removing toxic substances from patients' bodies. However, the efficacy and safety of IHD in infants and young children with inborn errors of metabolism are still not clear.

METHODS

This retrospective study included patients with urea cycle disorders, maple syrup urine disease, and methylmalonic acidemia who received IHD or non-IHD RRT at our hospital between 2001 and 2012 to remove ammonia, leucine, or methylmalonic acid. Both the efficacy and safety of the RRT were evaluated.

RESULTS

Thirty-five courses of RRT, including 25 courses of IHD and ten courses of non-IHD RRT, for 15 patients were included in the analysis. Before 2006, non-IHD RRT procedures, including peritoneal dialysis (PD) and continuous venous-venous hemofiltration (CVVH), were the most often used; from 2006 onwards IHD was used. There was one procedure-unrelated death. Catheter penetration occurred in one course of IHD. The efficacy data revealed that both the median duration of dialysis and the median 50 % toxin reduction time were shorter in IHD than in non-IHD RRT.

CONCLUSIONS

In infants and young children with inborn errors of metabolism, IHD is safe and more efficient than non-IHD RRT at removing toxins.

Maple syrup urine disease (MSUD): a case with long-term follow-up after liver transplantation

Maple syrup urine disease (MSUD) is a rare hereditary metabolic condition where the body is unable to breakdown amino acids causing toxic buildup. Acute and long-term management of MSUD involves a restricted diet and regular monitoring of amino acid levels; however, more recently liver transplants have been shown to be successful in treating this condition. Even with successful management of MSUD there is evidence from pediatric cases that shows a distinct pattern of neurocognitive deficits associated with this condition, including impaired nonverbal skills and psychomotor functioning with relatively intact verbal abilities. In the present paper, we report an adult case of MSUD with associated neurocognitive deficits and functional limitations following liver transplantation. Neuroimaging revealed no structural abnormalities, while the results from the neuropsychological evaluation showed impairment in visual-spatial processing, attention, executive functioning, and psychomotor abilities, with relative strengths in verbal skills. The patient also showed reduced adaptive functioning and mild anxiety. This case demonstrates neurocognitive deficiencies within the context of normal magnetic resonance imaging. The possible underlying mechanism of this neuropsychological profile is discussed in relation to other neurodevelopmental models.

The neuropsychiatry of inborn errors of metabolism

A number of metabolic disorders that affect the central nervous system can present in childhood, adolescence or adulthood as a phenocopy of a major psychiatric syndrome such as psychosis, depression, anxiety or mania. An understanding and awareness of secondary syndromes in metabolic disorders is of great importance as it can lead to the early diagnosis of such disorders. Many of these metabolic disorders are progressive and may have illness-modifying treatments available. Earlier diagnosis may prevent or delay damage to the central nervous system and allow for the institution of appropriate treatment and family and genetic counselling. Metabolic disorders appear to result in neuropsychiatric illness either through disruption of late neurodevelopmental processes (metachromatic leukodystrophy, adrenoleukodystrophy, GM2 gangliosidosis, Niemann-Pick type C, cerebrotendinous xanthomatosis, neuronal ceroid lipofuscinosis, and alpha mannosidosis) or via chronic or acute disruption of excitatory/inhibitory or monoaminergic neurotransmitter systems (acute intermittent porphyria, maple syrup urine disease, urea cycle disorders, phenylketonuria and disorders of homocysteine metabolism). In this manuscript we review the evidence for neuropsychiatric illness in major metabolic disorders and discuss the possible models for how these disorders result in psychiatric symptoms. Treatment considerations are discussed, including treatment resistance, the increased propensity for side-effects and the possibility of some treatments worsening the underlying disorder.

Young adults with MSUD and their transition to adulthood: psychosocial issues

Maple Syrup Urine Disease (MSUD) is an autosomal recessive condition with an incidence of 1 in 185,000 births worldwide. Regardless of the type of MSUD, treatment includes immediate and lifelong dietary restriction of isoleucine, leucine and valine. There is little known about the psychosocial impact of MSUD on the developmental milestones of emerging adulthood. We used a qualitative case study approach to explore the human experiences of MSUD on young adults (n = 8) and parents (n = 8). All participants were administered a semi-structured, qualitative interview as well as quantitative measures. Six core themes emerged: 1) lifelong strain of dietary management; 2) social isolation from peers and impact on dating; 3) impact of MSUD on academics and employment; 4) medical experiences and transition to adult care; 5) impact on family functioning; and 6) positive effects and growth. The results of this investigation highlight and expand awareness of the psychological and social needs of young adults with MSUD. This study calls for a collaborative, multidisciplinary effort in the treatment of these patients and their families.

Liver transplantation for classical maple syrup urine disease: long-term follow-up in 37 patients and comparative United Network for Organ Sharing experience

OBJECTIVE

To assess clinical and neurocognitive function in children who have undergone liver transplantation for classical maple syrup urine disease (MSUD).

STUDY DESIGN

A total of 35 patients with classical MSUD (age 9.9 ± 7.9 years) underwent liver transplantation between 2004 and 2009. Six patients donated their liver to recipients without MSUD ("domino" transplant). We analyzed clinical outcomes for our cohort and 17 additional cases from the national United Network for Organ Sharing registry; 33 patients completed IQ and adaptive testing before transplantation, and 14 completed testing 1 year later.

RESULTS

Patient and graft survival were 100% at 4.5 ± 2.2 years of follow-up. Liver function was normal in all patients. Branched-chain amino acid levels were corrected within hours after surgery and remained stable, with leucine tolerance increasing more than 10-fold. All domino transplant recipients were alive and well with normal branched-chain amino acid homeostasis at the time of this report. Patient and graft survival for all 54 patients with MSUD undergoing liver transplantation in the United States during this period were 98% and 96%, respectively. One-third of our patients were mentally impaired (IQ ≤ 70) before transplantation, with no statistically significant change 1 year later.

CONCLUSION

Liver transplantation is an effective long-term treatment for classical MSUD and may arrest brain damage, but will not reverse it.

Cognitive and adaptive functioning after liver transplantation for maple syrup urine disease: a case series

MSUD is a complex metabolic disorder that has been associated with central nervous system damage, developmental delays, and neurocognitive deficits. Although liver transplantation provides a metabolic cure for MSUD, changes in cognitive and adaptive functioning following transplantation have not been investigated. In this report, we present data from 14 patients who completed cognitive and adaptive functioning testing pre- and one yr and/or three yr post-liver transplantation. Findings show either no significant change (n=8) or improvement (n=5) in IQ scores pre- to post-liver transplantation. Greater variability was observed in adaptive functioning scores, but the majority of patients evidenced no significant change (n=8) in adaptive scores. In general, findings indicate that liver transplantation minimizes the likelihood of additional central nervous system damage, providing an opportunity for possible stabilization or improvement in neurocognitive functioning.

Neurocognitive profile in a case of maple syrup urine disease

Maple Syrup Urine Disease (MSUD) is a metabolic disease with associated enzyme deficiency and an inability to break down amino acids. Neurotoxic levels can occur resulting in neurological sequelae. Information regarding cognitive functions has suggested greater verbal than visuospatial abilities. Specific neuropsychological functions have not been studied. The objective of this study is to examine the neuropsychological profile in a case of MSUD. We present a case study of a 7-year-old female who has a history of late diagnosis (7 days of age) and poor metabolic control. Consistent with existing literature, a profile of stronger verbal reasoning and memory skills compared with visual-perceptual and nonverbal memory was revealed. Additional weaknesses were demonstrated with attention, emerging executive functions, and fine motor control. The results suggest that while previously described nonverbal reasoning and visuospatial impairments are present, there is likely a more complex pattern of neuropsychological impairments in children with MSUD, especially those with poor metabolic control.

Animal models of maple syrup urine disease

Maple syrup urine disease (MSUD) is an inherited aminoacidopathy resulting from dysfunction of the branched-chain keto acid dehydrogenase (BCKDH) complex. This disease is currently treated primarily by dietary restriction of branched-chain amino acids (BCAAs). However, dietary compliance is often challenging. Conversely, liver transplantation significantly improves outcomes, but donor organs are scarce and there are high costs and potential risks associated with this invasive procedure. Therefore, improved treatment options for MSUD are needed. Development of novel treatments could be facilitated by animal models that accurately mimic the human disease. Animal models provide a useful system in which to explore disease mechanisms and new preclinical therapies. Here we review MSUD and currently available animal models and their corresponding relevance to the human disorder. Using animal models to gain a more complete understanding of the pathophysiology behind the human disease may lead to new or improved therapies to treat or potentially cure the disorder.

Psychosocial Issues in Families Affected by Maple Syrup Urine Disease

The primary aim of this study was to ascertain the psychosocial issues faced by families affected by maple syrup urine disease (MSUD). The psychosocial adjustment and quality of life of children with MSUD were also described. Participants included 55 families and their children (ages 5 to 18 years) and teachers. Measures included a MSUD Family Survey, the Behavior Assessment System for Children (BASC) and the Pediatric Quality of Life Inventory (PedsQL). Parents reported via the MSUD Family Survey that the greatest sources of stress were financial and emotional. Many parents reported difficulty interacting with the medical staff and with schools. On the BASC, half of the children fell within the average range in psychosocial adjustment, although there were elevations in scales measuring attention, hyperactivity, and learning problems. On the PedsQL, the mean quality of life scores were closer to children with cancer than to a healthy sample. Despite the emotional and financial burden, parents reported that MSUD has also had a positive influence on their lives, leading to a world-view that is more compassionate and caring.

Synaptic plasma membrane Na(+), K (+)-ATPase activity is significantly reduced by the alpha-keto acids accumulating in maple syrup urine disease in rat cerebral cortex

The objective of the present study was to investigate the in vitro effects of the branched-chain alpha-keto acids accumulating in maple syrup urine disease, namely L-2-ketoisocaproic acid, L-2-keto-3-methylvaleric acid and L-2-ketoisovaleric acid on Na(+), K(+)-ATPase activity in synaptic plasma membranes from cerebral cortex of 35-day-old rats. All keto acids significantly inhibited Na(+), K(+)-ATPase activity at concentrations similar (1 mM) or even lower (0.5 mM) than those found in blood and cerebrospinal fluid of maple syrup urine disease patients. We also tested the effects of alanine on this enzyme activity. Alanine per se did not alter Na(+), K(+)-ATPase activity, but totally prevented the branched-chain alpha-keto acids-induced Na(+), K(+)-ATPase inhibition, indicating that alanine and the keto acids may possibly bind to the same site on the enzyme. We also observed that the branched-chain amino acids leucine, isoleucine and valine also inhibited Na(+) K(+)-ATPase activity to a similar degree as that of the branched-chain alpha-keto acids and that alanine was able to fully prevent these effects. Considering that Na(+), K(+)-ATPase is a critical enzyme for normal brain development and functioning, it is presumed that these findings may be involved in the pathophysiology of the neurological dysfunction of maple syrup urine disease.

Maple syrup urine disease: favourable effect of early diagnosis by newborn screening on the neonatal course of the disease

BACKGROUND

In the rare autosomal recessive disorder maple syrup urine disease (MSUD) the accumulation of the branched-chain amino acids and their metabolic products results in acute and chronic brain dysfunction. Since 2002, MSUD has been part of the extended newborn screening programme in Germany and Austria. Early diagnosis and intervention during the presymptomatic or early symptomatic period should improve the outcome of the patients, which would make the case for screening for MSUD.

AIM

The aim of the study was to evaluate the clinical course and alterations of marker metabolites during the first weeks of life in 10 patients with classical MSUD detected by newborn screening (NBS) in comparison with the 10 youngest German patients diagnosed clinically.

METHOD

Laboratory data as well as information on clinical course and management during the neonatal period were obtained retrospectively.

RESULTS

Patients detected in NBS presented with lower plasma leucine concentrations at confirmation of diagnosis and less severe clinical symptoms. Lowering of leucine to below a critical threshold of 1000 micromol/L was achieved earlier than in patients diagnosed on clinical grounds.

CONCLUSION

After diagnosis in screening, treatment can be initiated before the occurrence of severe metabolic decompensation. However, a favourable effect can only be achieved with immediate transfer of the neonate to a metabolic centre for adequate treatment in case of a positive screening result.

Renal replacement therapy in the treatment of confirmed or suspected inborn errors of metabolism

OBJECTIVE

Analysis of mortality and risk factors for mortality in the use of renal replacement therapy to correct metabolic disturbances associated with confirmed or suspected inborn errors of metabolism.

STUDY DESIGN

A retrospective review of an institutional review board-approved pediatric acute renal failure data base at the University of Michigan. Eighteen patients underwent 21 renal replacement therapy treatments for metabolic disturbances caused by urea cycle defects (n = 14), organic acidemias (n = 5), idiopathic hyperammonemia (n = 1), and Reye syndrome (n = 1).

RESULTS

There were 14 boys (74%) and 4 girls (26%), with a mean age and weight of 56.2 +/- 71.0 months and 18.5 +/- 19.2 kg, respectively, at the initiation of renal replacement therapy. Overall treatment mortality rate was 57.2% (12 of 21 treatments), with 11 of the 18 patients (61.1%) dying before hospital discharge. Two-year follow-up on those patients demonstrated that 5 patients (71.4%) remained alive. Initial therapy with hemodialysis was associated with improved survival. Ten treatments (47.6%) required transition to another form of renal replacement therapy to maintain ongoing metabolic control, with a mean duration of 6.1 +/- 9.8 days. Time to renal replacement therapy >24 hours was associated with an increased risk of mortality, whereas a blood pressure >5th percentile for age at the initiation of therapy and the use of anticoagulation were associated with a decreased risk of mortality.

CONCLUSIONS

Renal replacement therapy can correct the metabolic disturbances that accompany suspected or confirmed inborn errors of metabolism. Our experience demonstrates an approximately 60% mortality rate associated with renal replacement treatment, with more than 70% of survivors living longer than 2 years.

Duration of extracorporeal therapy in acute maple syrup urine disease: a kinetic model

Maple syrup urine disease (MSUD, MIM 248600) can be complicated by metabolic crises necessitating extracorporeal removal therapy (ECRT). Since leucine levels are usually not immediately available during therapy, an accurate kinetic model of leucine plasma levels during removal would be useful to establish the duration of ECRT. Such a kinetic model is available for neonates undergoing continuous ECRT (CECRT) with a leucine clearance>or=35 ml min-1 1.73 m-2. The current study tests the validity of this model in older children. Plasma leucine levels were obtained from eleven ECRT sessions [seven CECRT and four intermittent hemodialysis (HDi) sessions] in seven children aged 1-14 years. No hemodynamic instability or neurological complications were observed during treatment. HDi provided a higher leucine clearance and required shorter sessions than CECRT (5.4+/-0.6 vs. 17.1+/-6.0 h). All patients regained precrisis neurological status except for one patient who had severe neurological damage (severe cerebral edema) at the time of dialysis and subsequently died despite efficient leucine removal. A leucine clearance>or=50 ml min-1 1.73 m-2 is required to obtain a kinetic model similar to that reported in neonates, both with CECRT and HDi. This model should be helpful in predicting the duration of therapy needed to attain desired leucine levels.

The longest-surviving patient with classical maple syrup urine disease

The clinical problems, dietary management and biochemical monitoring over a 40-year period of the longest-surviving patient with maple syrup urine disease are described. Her case illustrates that a good outcome can be obtained with early diagnosis and institution of a diet restricted in branched-chain amino acids. Changes in dietary supplementation have benefited her in terms of nutrition and quality of life. Consistently high blood concentrations of branched-chain amino acids have not been associated with neuropsychometric decline.

Neuropsychometric outcome predictors for adults with maple syrup urine disease

We describe 14 adult MSUD patients (3 with intermediate MSUD) with varied clinical and neuropsychometric outcomes. Age at diagnosis appears to be a predictor of IQ even in adults, while long-term blood leucine does not correlate with IQ.

Impact of longitudinal plasma leucine levels on the intellectual outcome in patients with classic MSUD

Maple syrup urine disease (MSUD) is an inherited deficiency of branched chain alpha-ketoacid dehydrogenase (BCKDH) activity impairing the degradation of the branched chain amino acids valine, leucine, and isoleucine. Classic MSUD may lead to severe neonatal encephalopathy including coma and impaired cognitive outcome in later life. Early start of dietary treatment and careful metabolic control may improve the outcome of patients with classic MSUD. The aim of this study was to investigate the impact of long-term metabolic control assessed by plasma leucine levels on cognitive outcome in patients with classic MSUD. Plasma leucine levels of 24 patients were obtained retrospectively for the first 6 y of life and yearly medians of mean plasma leucine levels were calculated. At the age of 6 y, IQ tests were performed. Yearly medians of mean plasma leucine levels yielded three homogeneous clusters (low, intermediate, high). Patients of the low cluster showed statistically significant higher IQ scores compared with those of those of intermediate and high clusters. Long-term plasma leucine levels are associated with impaired cognitive outcome in patients with classic MSUD. To achieve the best possible intellectual outcome for affected individuals, we recommend that in infants and preschool children the target range for plasma leucine should not exceed 200 micromol/L.

Diagnosis of MSUD by newborn screening allows early intervention without extraneous detoxification

Maple syrup urine disease (MSUD) is a genetic metabolic disorder resulting from the defective activity of branched-chain 2-ketoacid dehydrogenase complex. Due to the metabolic block, high concentrations of the branched-chain amino acids (BCAA) leucine, valine, isoleucine, and allo-isoleucine as well as their corresponding branched-chain 2-keto acids accumulate in patients on a BCAA-unrestricted diet or during episodes with increased protein catabolism. Early diagnosis and management are essential to prevent permanent brain damage. Newborn screening by tandem MS allows for detection of elevated BCAA concentrations in blood in patients with classical MSUD before they show severe encephalopathic symptoms. Here, we report that newborn screening by expanded tandem MS enables for reversing the intoxication in newborns with MSUD within 24-48 h without any need for extraneous detoxification and thus decreasing the risk of brain damage during a particularly vulnerable period.

Infusionstherapie und Ernährung von Risikogruppen

Besondere Situationen erfordern ein besonderes Vorgehen. Während bisher das »Standardvorgehen« bezüglich der Ernährung von pädiatrischen Patienten dargestellt wurde, beschäftigt sich das vorliegende Kapitel mit »Sondersituationen« der pädiatrischen Infusionstherapie und Ernährung. Behandlungssituationen, die ein besonderes Vorgehen bei der Therapie oder spezielle Aufmerksamkeit bei der Anpassung der Ernährung erfordern, entstehen in der Regel durch 4 mögliche Situationen:

spezifische Physiologie von Patientengruppen (z. B. Früh- oder Neugeborene),

Auswirkungen von therapeutischen Maßnahmen (z. B. Operationen),

Pathophysiologie von Erkrankungen (z. B. angeborene Stoffwechselerkrankungen, Erkrankungen des onkologischen, rheumatischen oder atopischen Formenkreises, Anorexia nervosa, Bulimie oder Adipositas) oder

besondere körperliche Belastungen [z. B. (Leistungs-)Sport].

Bekannte Strategien werden systematisch und prägnant dargestellt und diskutiert.

Die Beschäftigung mit der Ernährung von »Risikogruppen« übt das Erkennen und den Umgang von potenziellen Gefahrensituationen bei der Verordnung von bilanzierter Ernährung. So sollte auch derjenige von dem Kapitel profitieren, der sich mit den behandelten Patientengruppen, Situationen, Erkrankungen üblicherweise nicht beschäftigen muss.

Frequencies of inherited organic acidurias and disorders of mitochondrial fatty acid transport and oxidation in Germany

The lack of epidemiological data on the frequency and/or burden of organic acidurias (OA) and mitochondrial fatty acid transport and oxidation disorders (mtFATOD) is one reason for hesitation to expand newborn screening (NBS) by tandem mass spectrometry (MS-MS). From 1999 to 2000, the frequency of ten potentially treatable OA and mtFATOD was assessed by active nation-wide surveillance on cases presenting with clinical symptoms using the German Paediatric Surveillance Unit (ESPED) system. Case ascertainment was complemented by a second independent source: 3-monthly inquiries in the metabolic laboratories performing secondary selected screening for OA and mtFATOD. Frequency estimates for clinically symptomatic cases older than 7 days in a birth cohort of 844,575 conventionally screened children was compared to the frequency found in a cohort of 382,247 screened by MS-MS in Bavaria and Baden-Württemberg. The overall frequency of the ten conditions considered was 1:8,000 (95% CI 1:11,000-1:6,000) by MS-MS as compared to 1:23,000 (95% CI 1:36,000-1:17,000) in symptomatic cases presenting mainly with metabolic crisis. The contributions of medium-chain acyl-CoA dehydrogenase deficiency (MCADD), other mtFATOD and OA were 29, 4 and 13 among the 46 cases identified by MS-MS, and 19, 1 and 13 among the 33 clinically symptomatic cases, respectively. Acute metabolic crisis, with a lethal outcome in four patients, was reported for 22/33 clinically symptomatic cases. No clinically symptomatic cases were reported from cohorts with screened by MS-MS.

CONCLUSION

ten potentially treatable organic acidurias and mitochondrial fatty acid transport and oxidations disorders were more common than phenylketonuria with organic acidurias accounting for 28% of the cases detected by newborn screening and 39% of the cases identified on high risk screening. These conditions were related to considerable morbidity and mortality. Considerations for their inclusion in expanded newborn screening programmes might be warranted.

Relationship of causative genetic mutations in maple syrup urine disease with their clinical expression

Maple syrup urine disease [MSUD] is a rare inborn error of metabolism inherited as an autosomal recessive trait through mutations in any of three different genes that encode components of the branched chain alpha-ketoacid dehydrogenase [BCKD] complex. In this work, the genotype of affected individuals was correlated with their clinical histories. These individuals were diagnosed and followed in a single centralized clinic, and their molecular genetic characterization was done by one laboratory. Three individuals had mutant alleles in the gene for the E1alpha component, five had mutations in the gene for E1beta, and three had mutations in the gene for E2. The results emphasize the diversity of the molecular and clinical presentations for individuals with MSUD and support the complexity of diseases termed "single gene traits." Of primary importance is early identification of at risk infants through newborn screening programs to minimize many of the complications associated with this protein intolerance. Attention to abnormal neurological signs in the neonate or evidence of neurological decompensation in older infants and children by a centralized medical management team minimizes permanent brain damage and improves survival.

Incidence and short-term outcome of children with symptomatic presentation of organic acid and fatty acid oxidation disorders in Germany

OBJECTIVE

To determine the incidence of symptomatic children with inherited organic acid disorders (OADs) and fatty acid oxidation disorders (FAODs) in Germany.

METHODS

An active surveillance of symptomatic children with inherited OADs and FAODs was conducted during a time period of 24 months (1999-2000) in Germany. Monthly inquiries were sent to all Departments of Pediatrics by the German Pediatric Surveillance Unit (ESPED) and quarterly to all specialized metabolic laboratories. Newly diagnosed patients were added to the database, recording clinical and biochemical information via a standardized questionnaire.

RESULTS

Prospective surveillance enrolling 844 575 children identified a total of 57 symptomatic children with newly diagnosed OADs or FAODs in states with conventional neonatal screening, resulting in an estimated cumulative incidence of 1:14 800. The most frequent diagnosis among these children was medium-chain acyl-CoA dehydrogenase deficiency (n = 20). The majority of symptomatic children revealed clinical symptoms during the first year of life (n = 36), frequently presenting with acute metabolic crises (n = 31). Eight children died during these crises. Notably, 47 of the symptomatic children suffered from diseases potentially detectable by expanded neonatal screening programs. This subgroup included 29 children presenting with metabolic crises and 7 of the 8 deaths.

CONCLUSIONS

Despite increased clinical awareness of OADs and FAODs, the mortality and morbidity for these children remains high, if they are diagnosed after manifestation of clinical disease. An introduction of nationwide neonatal screening programs would change the focus for organic acid analysis from patients presenting with acute metabolic crises to more chronic clinical presentations, especially the cerebral organic acid disorders.

Branched-chain organic acidurias

Branched chain organic acidurias are a group of disorders that result from an abnormality of specific enzymes involving the catabolism of branched chain amino acids (leucine, isoleucine, valine). Maple syrup urine disease (MSUD), isovaleric acidaemia (IVA), propionic aciduria (PA) and methylmalonic aciduria (MMA) represent the most commonly encountered abnormal organic acidurias. All these four disorders present in neonates as a neurologic distress of the intoxication type with either ketosis or ketoacidosis and hyperammonaemia. There is a free interval between birth and clinical symptoms. MMA, PA and IVA present with a severe dehydration, leuconeutropenia and thrombopenia which can mimic sepsis. All these disorders can be diagnosed by identifying acylcarnitine and other organic acid compounds in plasma and urine by gas chromatography mass spectrometry or tandem MS-MS. These disorders are amenable to treatment by removing toxic compounds and by using special diets and carnitine.

Is demyelination a feature of maple syrup urine disease?

To determine whether disturbance of myelination is a pathophysiologic feature in patients with treated maple syrup urine disease (MSUD), neurophysiologic studies were performed in 10 MSUD patients ages 4-16 years. Afferent and efferent pathways were studied by visual evoked potentials, somatosensory evoked potentials, motor evoked potentials, stance-stabilizing reflexes, and peripheral nerve conduction velocity. Magnetic resonance imaging was used to detect possible cerebral white matter abnormalities. Visual evoked potentials were normal in all patients. There was only slight prolongation of central afferent and efferent conduction times and the long latency component of the stance-stabilizing reflexes. Peripheral nerve conduction studies revealed reduced sensory nerve conduction velocity in 3 patients. The neurophysiologic findings were not consistently correlated to the neurologic outcome of the patients. Magnetic resonance imaging did not reveal major abnormalities and demonstrated bilateral periventricular high intensity periventricular signals on T2-weighted images in 4 of 10 patients. It is concluded that dysmyelination is not a major pathophysiologic feature in patients with MSUD.