Neurological outcome in long-chain hydroxy fatty acid oxidation disorders

OBJECTIVE

This study aims to elucidate the long-term benefit of newborn screening (NBS) for individuals with long-chain 3-hydroxy-acyl-CoA dehydrogenase (LCHAD) and mitochondrial trifunctional protein (MTP) deficiency, inherited metabolic diseases included in NBS programs worldwide.

METHODS

German national multicenter study of individuals with confirmed LCHAD/MTP deficiency identified by NBS between 1999 and 2020 or selective metabolic screening. Analyses focused on NBS results, confirmatory diagnostics, and long-term clinical outcomes.

RESULTS

Sixty-seven individuals with LCHAD/MTP deficiency were included in the study, thereof 54 identified by NBS. All screened individuals with LCHAD deficiency survived, but four with MTP deficiency (14.8%) died during the study period. Despite NBS and early treatment neonatal decompensations (28%), symptomatic disease course (94%), later metabolic decompensations (80%), cardiomyopathy (28%), myopathy (82%), hepatopathy (32%), retinopathy (17%), and/or neuropathy (22%) occurred. Hospitalization rates were high (up to a mean of 2.4 times/year). Disease courses in screened individuals with LCHAD and MTP deficiency were similar except for neuropathy, occurring earlier in individuals with MTP deficiency (median 3.9 vs. 11.4 years; p = 0.0447). Achievement of dietary goals decreased with age, from 75% in the first year of life to 12% at age 10, and consensus group recommendations on dietary management were often not achieved.

INTERPRETATION

While NBS and early treatment result in improved (neonatal) survival, they cannot reliably prevent long-term morbidity in screened individuals with LCHAD/MTP deficiency, highlighting the urgent need of better therapeutic strategies and the development of disease course-altering treatment.

Fifty years of research on mitochondrial fatty acid oxidation disorders: The remaining challenges

Since the identification of the first disorder of mitochondrial fatty acid oxidation defects (FAOD) in 1973, more than 20 defects have been identified. Although there are some differences, most FAOD have similar clinical signs, which are mainly due to energy depletion and toxicity of accumulated metabolites. However, some of them have an unusual clinical phenotype or specific clinical signs. This manuscript focuses on what we have learnt so far on the pathophysiology of these disorders, which present with clinical signs that are not typical of categorical FAOD. It also highlights that some disorders have not yet been identified and tries to make assumptions to explain why. It also deals with new treatments under consideration in FAOD, including triheptanoin and similar anaplerotic substrates, ketone body treatments, RNA and gene therapy approaches. Finally, it suggests challenges for the diagnosis of FAOD in the coming years, both for symptomatic patients and for those diagnosed through newborn screening. The ultimate goal would be to identify all the patients born with FAOD and ensure for them the best possible quality of life.

Update on Sitosterolemia and Atherosclerosis

PURPOSE OF REVIEW

The purpose of this review was to summarize important and updated information on sitosterolemia. Sitosterolemia is an inherited lipid disorder consisting of high levels of plasma plant sterols. This sterol storage condition is caused by biallelic loss-of-function genetic variants in either ABCG5 or ABCG8, leading to increased intestinal absorption and decreased hepatic excretion of plant sterols. Clinically, patients with sitosterolemia usually exhibit xanthomatosis, high levels of plasma cholesterol, and premature atherosclerotic disease, but presentation can be highly heterogeneous. Therefore, recognition of this condition requires a high level of suspicion, with confirmation upon genetic diagnosis or through measurement of plasma phytosterols. Treatment of sitosterolemia with both a plant sterol-restricted diet and the intestinal cholesterol absorption inhibitor ezetimibe can reduce efficiently the levels of plasma plant sterols, consisting in the first-line therapy for this disease.

RECENT FINDINGS

Since hypercholesterolemia is often present in individuals with sitosterolemia, it is important to search for genetic variants in ABCG5 and ABCG8 in patients with clinical criteria for familial hypercholesterolemia (FH), but no variants in FH implicated genes. Indeed, recent studies have suggested that genetic variants in ABCG5/ABCG8 can mimic FH, and even when in heterozygosis, they may potentially exacerbate the phenotype of patients with severe dyslipidemia. Sitosterolemia is a genetic lipid disorder characterized by increased circulating levels of plant sterols and clinically manifested by xanthomatosis, hematologic disorders, and early atherosclerosis. Awareness about this condition, a rare, but commonly underdiagnosed and yet treatable cause of premature atherosclerotic disease, is imperative.

Synthetic mRNA rescues very long-chain acyl-CoA dehydrogenase deficiency in patient fibroblasts and a murine model

Very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency is an inborn error of long chain fatty acid β-oxidation (FAO) with limited treatment options. Patients present with heterogeneous clinical phenotypes affecting predominantly heart, liver, and skeletal muscle. While VLCAD deficiency is a systemic disease, restoration of liver FAO has the potential to improve symptoms more broadly due to increased total body ATP production and reduced accumulation of potentially toxic metabolites. We explored the use of synthetic human VLCAD (hVLCAD) mRNA and lipid nanoparticle encapsulated hVLCAD mRNA (LNP-VLCAD) to generate functional VLCAD enzyme in patient fibroblasts derived from VLCAD deficient patients, mouse embryonic fibroblasts, hepatocytes isolated from VLCAD knockout (Acadvl-/-) mice, and Acadvl-/- mice to reverse the metabolic effects of the deficiency. Transfection of all cell types with hVLCAD mRNA resulted in high level expression of protein that localized to mitochondria with increased enzyme activity. Intravenous administration of LNP-VLCAD to Acadvl-/- mice produced a significant amount of VLCAD protein in liver, which declined over a week. Treated Acadvl-/- mice showed reduced hepatic steatosis, were more resistant to cold stress, and accumulated less toxic metabolites in blood than untreated animals. Results from this study support the potential for hVLCAD mRNA for treatment of VLCAD deficiency.

Towards values-based healthcare for inherited metabolic disorders: An overview of current practices for persons with liver glycogen storage disease and fatty acid oxidation disorders

Value-based healthcare (VBHC) intends to achieve better outcomes for patients, to improve quality of patient care, with reduced costs. Four dimensions define a model of intimately related value-pillars: personal value, allocative value, technical value, and societal value. VBHC is mostly applied in common diseases, and there are fundamental challenges in applying VBHC strategies to low volume, high complex healthcare situations, such as rare diseases, including inherited metabolic disorders. This article summarizes current practices at various academical domains (i.e., research, healthcare, education, and training) that (aim to) increase values at various value-pillars for persons with liver glycogen storage diseases or fatty acid oxidation disorders and their families. Future perspectives may include facilitating virtual networks to function as integrated practice units, improving measurement of outcomes, and creating information technology platforms to overcome the ethical, legal, societal, and technical challenges of data sharing for healthcare and research purposes.

Characterization of exonic variants of uncertain significance in very long-chain acyl-CoA dehydrogenase identified through newborn screening

Very long-chain acyl-CoA dehydrogenase deficiency (VLCADD) is an autosomal recessive disease resulting from mutations in the ACADVL gene and is among the disorders tested for in newborn screening (NBS). Confirmatory sequencing following suspected VLCADD NBS results often identifies variants of uncertain significance (VUS) in the ACADVL gene, leading to uncertainty of diagnosis and providing effective treatment regimen. Currently, ACADVL has >300 VUSs in the ClinVar database that requiring characterization to determine potential pathogenicity. In this study, CRISPR/Cas9 genome editing was used to knock out ACADVL in HEK293T cells, and targeted deletion was confirmed by droplet digital polymerase chain reaction (PCR). No VLCAD protein was detected and an 84% decrease in enzyme activity using the electron transfer flavoprotein fluorescence reduction assay and C21-CoA as substrate was observed compared to control. Plasmids containing control or variant ACADVL coding sequence were transfected into the ACADVL null HEK293T. While transfection of control ACADVL restored VLCAD protein and enzyme activity, cells expressing the VLCAD Val283Ala mutant had 18% VLCAD enzyme activity and reduced protein compared to control. VLCAD Ile420Leu, Gly179Arg, and Gln406Pro produced protein comparable to control but 25%, 4%, and 5% VLCAD enzyme activity, respectively. Leu540Pro and Asp570_Ala572dup had reduced VLCAD protein and 10% and 3% VLCAD enzyme activity, respectively. VLCADD fibroblasts containing the same variations had decreased VLCAD protein and activity comparable to the transfection experiments. Generating ACADVL null HEK293T cell line allowed functional studies to determine pathogenicity of ACADVL exonic variants. This approach can be applied to multiple genes for other disorders identified through NBS.

Pediatric single large-scale mtDNA deletion syndromes: The power of patient reported outcomes

There is a limited understanding of system-level clinical outcomes and interventions associated with single large-scale mitochondrial DNA deletion syndromes (SLSMDS). Additionally, no research exists that describes patient reported outcomes (PROs) of children with SLSMDS. A global and observational registry was established to understand the multi-systemic course of SLSMDS and track clinical outcomes. The development and design of the registry is described. Demographic characteristics, history and diagnoses, and system level prevalence of problems and interventions are reported for 42 children. System level problems and interventions include information on the following body systems: audiology, cardiac, endocrine, gastrointestinal (including pancreatic and hepatobiliary system), hematological, metabolic, neurological (including autonomic, mobility, & learning), ophthalmic, psychiatric, renal, and respiratory. Results emphasize the need of patient registries and suggest that the diagnostic odyssey and burden of disease for children with SLSMDS is significant. System-level findings may help families and clinical providers with diagnosis, prognostication, and treatment. A multidisciplinary team of clinical experts with a central coordinating specialist for children with SLSMDS is recommended.

Management Principles for Acute Illness in Patients With Medium-Chain Acyl-Coenzyme A Dehydrogenase Deficiency

Medium-chain acyl-coenzyme A dehydrogenase deficiency (MCADD) is a fatty acid oxidation disorder in which the patient is unable to break down fats to produce energy. This disorder places children at risk for metabolic decompensation during periods of stress, such as routine childhood illnesses. The intent of this clinical report is to provide pediatricians with additional information regarding the acute clinical care of patients with MCADD. Although each patient with MCADD will still be expected to have a primary metabolic physician, the involvement of the primary care provider is crucial as well. Appropriate treatment of children with MCADD can lead to avoidance of morbidity and mortality.

Clinical manifestations and management of fatty acid oxidation disorders

Fatty acid oxidation disorders (FAOD) are a group of rare, autosomal recessive, metabolic disorders caused by variants of the genes for the enzymes and proteins involved in the transport and metabolism of fatty acids in the mitochondria. Those affected by FAOD are unable to convert fatty acids into tricarboxylic acid cycle intermediates such as acetyl-coenzyme A, resulting in decreased adenosine triphosphate and glucose for use as energy in a variety of high-energy-requiring organ systems. Signs and symptoms may manifest in infants but often also appear in adolescents or adults during times of increased metabolic demand, such as fasting, physiologic stress, and prolonged exercise. Patients with FAOD present with a highly heterogeneous clinical spectrum. The most common clinical presentations include hypoketotic hypoglycemia, liver dysfunction, cardiomyopathy, rhabdomyolysis, and skeletal myopathy, as well as peripheral neuropathy and retinopathy in some subtypes. Despite efforts to detect FAOD through newborn screening and manage patients early, symptom onset can be sudden and serious, even resulting in death. Therefore, it is critical to identify quickly and accurately the key signs and symptoms of patients with FAOD to manage metabolic decompensations and prevent serious comorbidities.

Effects of fasting, feeding and exercise on plasma acylcarnitines among subjects with CPT2D, VLCADD and LCHADD/TFPD

BACKGROUND

The plasma acylcarnitine profile is frequently used as a biochemical assessment for follow-up in diagnosed patients with fatty acid oxidation disorders (FAODs). Disease specific acylcarnitine species are elevated during metabolic decompensation but there is clinical and biochemical heterogeneity among patients and limited data on the utility of an acylcarnitine profile for routine clinical monitoring.

METHODS

We evaluated plasma acylcarnitine profiles from 30 diagnosed patients with long-chain FAODs (carnitine palmitoyltransferase-2 (CPT2), very long-chain acyl-CoA dehydrogenase (VLCAD), and long-chain 3-hydroxy acyl-CoA dehydrogenase or mitochondrial trifunctional protein (LCHAD/TFP) deficiencies) collected after an overnight fast, after feeding a controlled low-fat diet, and before and after moderate exercise. Our purpose was to describe the variability in this biomarker and how various physiologic states effect the acylcarnitine concentrations in circulation.

RESULTS

Disease specific acylcarnitine species were higher after an overnight fast and decreased by approximately 60% two hours after a controlled breakfast meal. Moderate-intensity exercise increased the acylcarnitine species but it varied by diagnosis. When analyzed for a genotype/phenotype correlation, the presence of the common LCHADD mutation (c.1528G > C) was associated with higher levels of 3-hydroxyacylcarnitines than in patients with other mutations.

CONCLUSIONS

We found that feeding consistently suppressed and that moderate intensity exercise increased disease specific acylcarnitine species, but the response to exercise was highly variable across subjects and diagnoses. The clinical utility of routine plasma acylcarnitine analysis for outpatient treatment monitoring remains questionable; however, if acylcarnitine profiles are measured in the clinical setting, standardized procedures are required for sample collection to be of value.

Long-chain fatty acid oxidation disorders and current management strategies

Long-chain fatty acid oxidation disorders (LC-FAODs) are rare, life-threatening, autosomal recessive genetic disorders characterized by acute crises of energy production and chronic energy deficiency. Patients may present with rhabdomyolysis induced by exercise; fasting or illness; hepatic dysfunction, including severe hypoglycemia and hyperammonemia; and cardiomyopathy. These clinical manifestations can lead to frequent hospitalizations and premature death. LC-FAODs are caused by mutations in nuclear genes encoding mitochondrial enzymes involved in the conversion of dietary long-chain fatty acids (LCFAs) into energy during times of fasting and physiologic stress. Despite newborn screening, current management options leave many patients continuing to experience major clinical events, and mortality rates remain elevated. The current standard therapy for LC-FAODs is avoidance of fasting and supplementation of medium-chain triglyceride oil, an even, medium-chain fatty acid that does not require the typical steps of LC-FAOD for metabolism. Despite this therapy, patients with LC-FAODs continue to experience recurring hospitalizations, and high morbidity and mortality rates. In recent years, the use of medium, odd-chain fatty acids, such as triheptanoin, have been studied as a treatment of LC-FAODs due to its anaplerotic properties. Due to favorable safety and efficacy data from clinical trials, this novel agent has the potential to transform the treatment of LC-FAODs and improve patient outcomes in this patient population. This article provides an overview of the epidemiology, pathophysiology, clinical manifestations, and current management approaches for the diagnosis and management of LC-FAODs. It also provides the most recent clinical safety and efficacy data for triheptanoin and other therapies under investigation.

AAV9 gene replacement therapy for respiratory insufficiency in very-long chain acyl-CoA dehydrogenase deficiency

Very-long chain acyl-CoA dehydrogenase (VLCAD) deficiency (VLCADD) is an autosomal recessive disorder of fatty acid oxidation. Fatty acids are a major source of energy during catabolic stress, so the absence of VLCAD can result in a metabolic crises and respiratory insufficiency. The etiology of this respiratory insufficiency is unclear. Thus, our aims were: (1) to characterize respiratory pathophysiology in VLCADD mice (VLCAD^-/- ), and (2) to determine if AAV9-mediated gene therapy improves respiratory function. For the first aim, VLCAD^-/- and wild-type (WT) mice underwent an exercise/fast "stress protocol" and awake spontaneous breathing was evaluated using whole-body plethysmography (WBP) both at baseline and during a hypercapnic respiratory challenge (FiO₂ : 0.21; FiCO₂ : 0.07; nitrogen balance). During hypercapnia, VLCAD ^-/- mice had a significantly lower frequency, tidal volume, minute ventilation, and peak inspiratory and expiratory flow, all of which indicate respiratory insufficiency. Histologically, the cardiac and respiratory muscles of stressed VLCAD ^-/- animals had an accumulation of intramyocellular lipids. For the second aim, a single systemic injection of AAV9-VLCAD gene therapy improved this respiratory pathology by normalizing breathing frequency and enhancing peak inspiratory flow. In addition, following gene therapy, there was a moderate reduction of lipid accumulation in the respiratory muscles. Furthermore, VLCAD protein expression was robust in cardiac and respiratory muscle. This was confirmed by immuno-staining with anti-human VLCAD antibody. In summary, stress with exercise and fasting induces respiratory insufficiency in VLCAD^-/- mice and a single injection with AAV9-VLCAD gene therapy ameliorates breathing.

Clinical and biochemical outcome of patients with very long-chain acyl-CoA dehydrogenase deficiency

BACKGROUND

Very-Long-Chain Acyl-CoA Dehydrogenase (VLCAD) deficiency is a disorder of fatty acid oxidation included in the recommended uniform newborn screening (NBS) panel in the USA. It can have variable clinical severity and there is limited information on the natural history of this condition, clinical presentation according to genotype and effectiveness of newborn screening.

METHODS

Retrospective data (growth parameters, morbidity, biochemical and genetic testing results) were collected from patients with VLCAD deficiency, to evaluate biochemical and clinical outcomes. Descriptive statistics was used for qualitative variables, while linear regression analysis was used to correlate continuous variables.

RESULTS

VLCAD deficiency (screened by measuring elevated levels of C14:1-carnitine in blood spots) was more frequent in Utah than the national average (1:27,617 versus 1:63,481) in the first ten years of screening. Twenty-six patients had a confirmed diagnosis of VLCAD deficiency using DNA testing or functional studies. The c.848T>C (p.V283A) variant in the ACADVL gene was the most frequent in our population. Novel variants (c.623-21A>G (IVS7-21A>G); c.1052C>T (p.T351I); c.1183-7A>G (IVS11-7A>G); c.1281G>C (p.W427C); c.1923G>C (p.L641F); c.1924G>A (p.V642M)) were identified in this study, with their pathogenicity remaining unclear in most cases. C14:1-carnitine levels decreased with age and significantly correlated with CK levels as index of muscle involvement. There were no cases of HELLP syndrome nor liver disease during pregnancies in the mothers of VLCAD patients. None of our patients developed cardiac involvement after birth and all patients had normal growth parameters while on treatment. Clinical manifestations were related to concomitant infections and altered biochemical parameters.

DISCUSSION

VLCAD deficiency can be identified by neonatal screening. Most patients compliant with therapy normalized biochemical parameters and had no major clinical manifestations. Complications were completely prevented with a relatively low number of pre-emptive ER visits or hospital admissions. It remains unclear whether neonatal screening is now identifying less severely affected patient or if complications will arise as subjects become older. Observation beyond puberty is necessary to fully understand the impact of VLCAD deficiency on morbidity in patients with VLCAD deficiency.

Generation, Characteristics and Clinical Trials of Ex Vivo Generated Tolerogenic Dendritic Cells

Dendritic cells (DCs) play a key role not only in the initiation of primary immune responses, but also in the development and maintenance of immune tolerance. Numerous protocols have been developed to generate tolerogenic DCs (tolDCs) ex vivo, and the therapeutic efficacy of ex vivo-generated tolDCs has been demonstrated in autoimmune disease animal models. Based on successes in small animal models, several clinical trials have been completed or are on-going in patients with autoimmune diseases such as rheumatoid arthritis, type 1 diabetes, multiple sclerosis, and Crohn's disease. Here we describe the methods used to generate tolDCs ex vivo, and the common features shared by tolDCs. In addition, we overview five completed clinical trials with reported outcomes and summarize the tolDC-based clinical trials that are currently registered with the U.S. National Institutes of Health. Although the number of tolDC-based clinical trials is much smaller than the hundreds of clinical trials using immunogenic DCs, tolDC-based treatment of autoimmune diseases is becoming a reality, and could serve as an innovative cellular therapy in the future.

Treatable massive pericardial effusion and hypertrophic cardiomyopathy in an infant with a novel homozygous ACADVL mutation: A case report

RATIONALE

Infantile-onset hypertrophic cardiomyopathy (HCMP) should be considered a largely genetic condition, although its onset is most often triggered by infection. Very long chain acyl-CoA dehydrogenase (VLCAD) deficiency is a rare autosomal recessive inborn error of mitochondrial fatty acid β-oxidation that often causes severe cardiomyopathy and/or sudden death during the neonatal period.

PATIENT CONCERNS

Herein, we report an infant with VLCAD deficiency who presented with severe cardiac manifestations, including massive pericardial effusion and HCMP. The subject's older sister died of unknown causes at three days of age; however, the subject exhibited a normal tandem mass-spectrometry profile during the neonatal period.

DIAGNOSES

During her later cardiac presentation, the subject's C-14 and C-18 levels became elevated, and she was determined, via the conducted molecular analysis, to harbor a novel homozygous frameshift mutation (c.103_112dup) in ACADVL.

INTERVENTIONS

After VLCAD deficiency diagnosis, the subject was treated with the administration of a medium chain triglyceride formula and fluid therapy.

OUTCOMES

The subject's cardiac status was markedly improved by the dietary intervention and fluid therapy.

LESSONS

This report highlights that genetic mutations should be investigated as possible causes of infantile-onset HCMP, and that early diagnosis and intervention can prevent mortality for patients with VLCAD deficiency.

Establishing core outcome sets for phenylketonuria (PKU) and medium-chain Acyl-CoA dehydrogenase (MCAD) deficiency in children: study protocol for systematic reviews and Delphi surveys

BACKGROUND

Inherited metabolic diseases (IMD) are a large group of rare single-gene disorders that are typically diagnosed early in life. There are important evidence gaps related to the comparative effectiveness of therapies for IMD, which are in part due to challenges in conducting randomized controlled trials (RCTs) for rare diseases. Registry-based RCTs present a unique opportunity to address these challenges provided the registries implement standardized collection of outcomes that are important to patients and their caregivers and to clinical providers and healthcare systems. Currently there is no core outcome set (COS) for studies evaluating interventions for paediatric IMD. This protocol outlines a study that will establish COS for each of two relatively common IMD in children, phenylketonuria (PKU) and medium-chain acyl-CoA dehydrogenase (MCAD) deficiency.

METHODS

This two-part study is registered with the Core Outcome Measures in Effectiveness Trials (COMET) initiative. Part 1 includes a rapid review and development of an evidence map to identify a comprehensive listing of outcomes reported in past studies of PKU and MCAD deficiency. The review follows established methods for knowledge synthesis, including a comprehensive search strategy, two stages of screening citations against inclusion/exclusion criteria by two reviewers working independently, and extraction of important data elements from eligible studies, including details of the outcomes collected and outcome measurement instruments. The review findings will inform part 2 of our study, a set of Delphi surveys to establish consensus on the highest priority outcomes for each condition. Healthcare providers, families of children with PKU or MCAD deficiency, and health system decision-makers will be invited to participate in two to three rounds of Delphi surveys. The design of the surveys will involve parents of children with IMD who are part of a family advisory forum.

DISCUSSION

This protocol is a crucial step in developing the capacity to launch RCTs with meaningful outcomes that address comparative effectiveness questions in the field of paediatric IMD. Such trials will contribute high-quality evidence to inform decision-making by patients and their family members, clinicians, and policy-makers.

Very long-chain acyl-CoA dehydrogenase (VLCAD-) deficiency-studies on treatment effects and long-term outcomes in mouse models

Very-long-chain-acyl-CoA-dehydrogenase deficiency is the most common disorder of mitochondrial long-chain fatty acid (LCFA) oxidation, with an incidence of 1:50,000-1:100,000 in newborns. Catabolic situations contribute to the aggravation of symptoms and induce severe metabolic derangement. Treatment for VLCAD-deficiency includes avoidance of fasting and a long-chain fat-restricted and fat-modified diet in which LCFAs are fully or partially replaced by medium-chain triglycerides (MCT). The aim of this work was to investigate the outcome and the effects of long-term treatment in a mouse model of VLCAD-deficiency. The application of a single MCT bolus in a mouse model of VLCAD-deficiency (VLCAD^-/- mice) immediately prior to exercise protected the muscles from the accumulation of acylcarnitines providing the required energy and it did not affect hepatic lipid metabolism. However, when MCT was applied over the course of a year as a regular part of the diet, female VLCAD^-/- mice developed a severe clinical phenotype comparable to the human metabolic syndrome. Indeed, they were characterized by massive visceral fat infiltration, hepatosteatosis, disturbed fatty acid composition, hyperlipidemia, and systemic oxidative stress. In contrast, male VLCAD^-/- mice seemed to be protected and displayed only signs of insulin resistance. Besides the sex-specific response to MCT supplementation with regard to the lipid metabolism, all VLCAD^-/- mice developed progressive cardiac dysfunction over time which worsened when they were treated with regular MCT resulting in severe dilated cardiomyopathy. While long term use of MCT oil in mice has adverse effects, no such effects have been demonstrated in humans, likely reflecting the differences in long chain fatty acid oxidation between the two species.

Chanarin-Dorfman Syndrome

Chanarin-Dorfman syndrome is a rare, genetically determined autosomal recessive disorder, characterised by the presence of lipid droplets in the cytoplasm of multiple tissues of the body, particularly in the blood leukocytes and congenital non-bullous icthyosiform erythroderma. In this paper, we report one-year child who presented with skin lesions since birth and hepatomegaly. Liver biopsy showed steatohepatitis; and peripheral blood smear confirmed Jordan`s anomaly, which is a permanent feature of Chanarin-Dorfman syndrome.

[Mass Screening for Inborn Errors of Metabolism]

Neonatal mass screening is a project aiming at the prevention of disorders by discovering and treating diseases which damage health left untreated in all newborns. The bacterial inhibition assay (BIA) was developed in about .1961 and used as the Guthrie method for a long time, but it was replaced by tandem mass spectrometry due to the recent development of mass spectrometers, and its nationwide introduction in Japan was completed. With this introduction, 13 diseases were newly included in screening. Fatty acid and organic acid metabolic disorders and urea cycle disorders were included, and favorable results have been obtained.

Variability in the clinical management of fatty acid oxidation disorders: results of a survey of Canadian metabolic physicians

INTRODUCTION

There is little robust empirical evidence on which to base treatment recommendations for fatty acid oxidation disorders. While consensus guidelines are important, understanding areas where there is a lack of consensus is also critical to inform priorities for future evaluative research.

METHODS

We surveyed Canadian metabolic physicians on the treatment of medium-chain acyl-CoA dehydrogenase (MCAD) deficiency, very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency, long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency, and mitochondrial trifunctional protein (MTP) deficiency. We ascertained physicians' opinions on the use of different interventions for the long-term management of patients as well as for the management of acute illness, focusing on identifying interventions characterized by high variability in opinions. We also investigated factors influencing treatment decisions.

RESULTS

We received 18 responses (response rate 45%). Participants focused on avoidance of fasting and increased meal frequency as interventions for the management of MCAD deficiency. For the long-chain disorders, avoidance of fasting remained the most consistently endorsed intervention, with additional highly endorsed treatments differing for VLCAD versus LCHAD/MTP deficiency. L-carnitine supplementation and restriction of dietary fat were characterized by high variability in physicians' opinions, as were several interventions specific to long-chain disorders. Social factors and patient characteristics were important influences on treatment decisions.

CONCLUSIONS

Based on our findings we suggest that high priority treatments for rigorous effectiveness studies could include L-carnitine supplementation (MCAD and LCHAD/MTP deficiencies), restriction of dietary fat, and, for the long-chain disorders, feeding practices for breastfed infants and the use of various supplements (essential fatty acids, carbohydrates, cornstarch, multivitamins).

[LDL-apheresis in patients with familial autosomal recessive hypercholesterolemia]

LDL-apheresis reduces the cardiovascular risk in patients with familial hypercholesterolemia. The addition of statin therapy in patients with autosomal recessive hypercholesterolemia may change the lipid profile to a less atherogenic pattern.

Fatty acid oxidation disorders: outcome and long-term prognosis

Assessing the outcome of fatty acid oxidation disorders is difficult, as most are rare. For diagnosis by newborn screening, the situation is compounded: far more cases are diagnosed by screening than by clinical presentation, representing a somewhat different cohort. The literature on outcome was reviewed. For disorders other than medium-chain acyl-coenzyme A (CoA) dehydrogenase (MCAD) deficiency there was insufficient evidence to make many firm statements. In MCAD deficiency, risk of death in the first 72 h is around 4%, with a further approximately 5-7% fatality rate in the first 6 years but very low subsequent risk in previously undiagnosed patients. The risk of death after diagnosis is very low at any age, with good management. The long-term outcome is good nowadays. Very-long-chain acyl-CoA dehydrogenase deficiency poses a risk of death in early infancy, but the condition is generally treatable, with a good outcome after diagnosis. Approximately 10-20% of patients diagnosed by newborn screening and treated nevertheless suffer episodic rhabdomyolysis. Some patients never become symptomatic. Isolated long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency is treatable, but most patients suffer episodic hypoketotic hypoglycaemia and rhabdomyolysis. Generalised mitochondrial tri-functional protein deficiency has high early mortality rate. A more insidious presentation also occurs, with symptoms sometimes confined to progressive axonal neuropathy. Among carnitine cycle disorders, carnitine transporter deficiency, potentially lethal, is uniformly successfully treated orally with carnitine. Carnitine-acylcarnitine translocase and early-onset carnitine palmitoyl transferase type II (CPT II) deficiencies have an extremely high neonatal mortality rate. Late-onset CPT II is characterised only by episodic rhabdomyolysis on severe exercise. CPT type IA deficiency may often be benign, although early presentation with hypoketotic hypoglycaemia certainly occurs.

Clinical aspects of short-chain acyl-CoA dehydrogenase deficiency

Short-chain acyl-CoA dehydrogenase deficiency (SCADD) is an autosomal recessive inborn error of mitochondrial fatty acid oxidation. SCADD is biochemically characterized by increased C4-carnitine in plasma and ethylmalonic acid in urine. The diagnosis of SCADD is confirmed by DNA analysis showing SCAD gene mutations and/or variants. SCAD gene variants are present in homozygous form in approximately 6% of the general population and considered to confer susceptibility to development of clinical disease. Clinically, SCADD generally appears to present early in life and to be most frequently associated with developmental delay, hypotonia, epilepsy, behavioral disorders, and hypoglycemia. However, these symptoms often ameliorate and even disappear spontaneously during follow-up and were found to be unrelated to the SCAD genotype. In addition, in some cases, symptoms initially attributed to SCADD could later be explained by other causes. Finally, SCADD relatives of SCADD patients as well as almost all SCADD individuals diagnosed by neonatal screening remained asymptomatic during follow-up. This potential lack of clinical consequences of SCADD has several implications. First, the diagnosis of SCADD should never preclude extension of the diagnostic workup for other potential causes of the observed symptoms. Second, patients and parents should be clearly informed about the potential lack of relevance of the disorder to avoid unfounded anxiety. Furthermore, to date, SCADD is not an optimal candidate for inclusion in newborn screening programs. More studies are needed to fully establish the relevance of SCADD and solve the question as to whether SCADD is involved in a multifactorial disease or represents a nondisease.

Clinical and biochemical monitoring of patients with fatty acid oxidation disorders

Evidence-based guidelines for monitoring patients with disorders in fatty acid oxidation (FAO) are lacking, and most protocols are based on expert statements. Here, we describe our protocol for Danish patients. Clinical monitoring is the most important measure and has the main aims of checking growth, development and diet and of bringing families to the clinic regularly to remind them of their child's risk and review how they cope and adjust, e.g. to an acute intercurrent illness. Most of these measures are simple and can be carried out during a routine out-patient visit; we seldom do more complicated assessments by a neuropsychologist, speech therapist, or physical and occupational therapists. Paraclinical measurements are not used for short-chain and medium-chain disorders; electrocardiography (including 24 h monitoring) and echocardiography are done for most patients with long-chain and carnitine transporter deficiencies. Eye examination is done in all, and liver ultrasonography in some patients with long-chain 3-hydroxyacyl-coenzyme A dehydrogenase/tri-functional protein (LCHAD/TFP) deficiencies. Biochemical follow-up includes determination of free carnitine and acylcarnitines. Free carnitine is measured to monitor carnitine supplementation in patients with multiple acyl-coenzyme A dehydrogenase deficiency (MADD) and carnitine transporter deficiency (CTD) and to follow metabolic control and disclose deficiency states in other FAO disorders. We are evaluating long-chain acylcarnitines in patients with long-chain disorders; so far there does not seem to be any clear-cut benefit in following these levels. An erythrocyte fatty acid profile is done in patients with long-chain disorders to test for essential fatty acid and docosahexanoic acid (DHA) deficiencies. The measurement of creatine kinase is helpful in long-chain disorders. Ongoing follow-up and education of the patient is important throughout life to prevent disease morbidity or death from metabolic crises.

Current issues regarding treatment of mitochondrial fatty acid oxidation disorders

Treatment recommendations in mitochondrial fatty acid oxidation (FAO) defects are diverse. With implementation of newborn screening and identification of asymptomatic patients, it is necessary to define whom to treat and how strictly. We here discuss critical questions that are currently under debate. For some asymptomatic long-chain defects, long-chain fat restriction plays a minor role, and a normal diet may be introduced. For patients presenting only with myopathic symptoms, e.g., during exercise, treatment may be adapted to energy demand. As a consequence, patients with exercise-induced myopathy may be able to return to normal activity when provided with medium-chain triglycerides (MCT) prior to exercise. There is no need to limit participation in sports. Progression of retinopathy in disorders of the mitochondrial trifunctional protein complex is closely associated with hydroxyacylcarnitine accumulation. A strict low-fat diet with MCT supplementation is recommended to slow or prevent progression of chorioretinopathy. Additional docosahexanoic acid does not prevent the decline in retinal function but does promote nonspecific improvement in visual acuity and is recommended. There is no evidence that L-carnitine supplementation is beneficial. Thus, supplementation with L-carnitine in a newborn identified by screening with either a medium-chain or long-chain defect is not supported. With respect to the use of the odd-chain medium-chain triglyceride triheptanoin in myopathic phenotypes, randomized trials are needed to establish whether triheptanoin is more effective than even-chain MCT. With increasing pathophysiological knowledge, new treatment options have been identified and are being clinically evaluated. These include the use of bezafibrates in myopathic long-chain defects.

The enzymology of mitochondrial fatty acid beta-oxidation and its application to follow-up analysis of positive neonatal screening results

Oxidation of fatty acids in mitochondria is a key physiological process in higher eukaryotes including humans. The importance of the mitochondrial beta-oxidation system in humans is exemplified by the existence of a group of genetic diseases in man caused by an impairment in the mitochondrial oxidation of fatty acids. Identification of patients with a defect in mitochondrial beta-oxidation has long remained notoriously difficult, but the introduction of tandem-mass spectrometry in laboratories for genetic metabolic diseases has revolutionalized the field by allowing the rapid and sensitive analysis of acylcarnitines. Equally important is that much progress has been made with respect to the development of specific enzyme assays to identify the enzyme defect in patients subsequently followed by genetic analysis. In this review, we will describe the current state of knowledge in the field of fatty acid oxidation enzymology and its application to the follow-up analysis of positive neonatal screening results.

Treatment recommendations in long-chain fatty acid oxidation defects: consensus from a workshop

Published data on treatment of fatty acid oxidation defects are scarce. Treatment recommendations have been developed on the basis of observations in 75 patients with long-chain fatty acid oxidation defects from 18 metabolic centres in Central Europe. Recommendations are based on expert practice and are suggested to be the basis for further multicentre prospective studies and the development of approved treatment guidelines. Considering that disease complications and prognosis differ between different disorders of long-chain fatty acid oxidation and also depend on the severity of the underlying enzyme deficiency, treatment recommendations have to be disease-specific and depend on individual disease severity. Disorders of the mitochondrial trifunctional protein are associated with the most severe clinical picture and require a strict fat-reduced and fat-modified (medium-chain triglyceride-supplemented) diet. Many patients still suffer acute life-threatening events or long-term neuropathic symptoms despite adequate treatment, and newborn screening has not significantly changed the prognosis for these severe phenotypes. Very long-chain acyl-CoA dehydrogenase deficiency recognized in neonatal screening, in contrast, frequently has a less severe disease course and dietary restrictions in many patients may be loosened. On the basis of the collected data, recommendations are given with regard to the fat and carbohydrate content of the diet, the maximal length of fasting periods and the use of l-carnitine in long-chain fatty acid oxidation defects.

Management and outcome in 75 individuals with long-chain fatty acid oxidation defects: results from a workshop

At present, long-chain fatty acid oxidation (FAO) defects are diagnosed in a number of countries by newborn screening using tandem mass spectrometry. In the majority of cases, affected newborns are asymptomatic at time of diagnosis and acute clinical presentations can be avoided by early preventive measures. Because evidence-based studies on management of long-chain FAO defects are lacking, we carried out a retrospective analysis of 75 patients from 18 metabolic centres in Germany, Switzerland, Austria and the Netherlands with special regard to treatment and disease outcome. Dietary treatment is effective in many patients and can prevent acute metabolic derangements and prevent or reverse severe long-term complications such as cardiomyopathy. However, 38% of patients with very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency had intermittent muscle weakness and pain despite adhering to therapy. Seventy-six per cent of patients with disorders of the mitochondrial trifunctional protein (TFP)-complex including long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency, had long-term myopathic symptoms. Of these, 21% had irreversible peripheral neuropathy and 43% had retinopathy. The main principle of treatment was a fat-reduced and fat-modified diet. Fat restriction differed among patients with different enzyme defects and was strictest in disorders of the TFP-complex. Patients with a medium-chain fat-based diet received supplementation of essential long-chain fatty acids. l-Carnitine was supplemented in about half of the patients, but in none of the patients with VLCAD deficiency identified by newborn screening. In summary, in this cohort the treatment regimen was adapted to the severity of the underlying enzyme defect and thus differed among the group of long-chain FAO defects.

Tolerance to fast: rational and practical evaluation in children with hypoketonaemia

Prolonged fasting in children with disorder of fat oxidation or ketone body synthesis can lead not only to hypoglycaemia but also to the accumulation of toxic metabolites. The length of time such patients can be safely fasted is important information for caregivers. Most children with MCAD deficiency when well can tolerate 'normal' periods without food, but in more severe disorders such as LCHAD deficiency even these may be associated with acute or chronic damage. Guidelines have been published for safe fasting periods in MCAD but not in other conditions. In the absence of such recommendations, a rational approach must be based on an understanding of the normal physiology of fasting in children of different ages and the pathophysiology associated with the child's particular disorder. Intercurrent infections pose a particular risk and may significantly reduce fasting tolerance.

A Delphi clinical practice protocol for the management of very long chain acyl-CoA dehydrogenase deficiency

INTRODUCTION

Very long chain acyl-CoA dehydrogenase (VLCAD) deficiency is a disorder of oxidation of long chain fat, and can present as cardiomyopathy or fasting intolerance in the first months to years of life, or as myopathy in later childhood to adulthood. Expanded newborn screening has identified a relatively high incidence of this disorder (1:31,500), but there is a dearth of evidence-based outcomes data to guide the development of clinical practice protocols. This consensus protocol is intended to assist clinicians in the diagnosis and management of screen-positive newborns for VLCAD deficiency until evidence-based guidelines are available.

METHOD

The Oxford Centre for Evidence-based Medicine system was used to grade the literature review and create recommendations graded from A (evidence level of randomized clinical trials) to D (expert opinion). Delphi was used as the consensus tool. A panel of 14 experts (including clinicians, diagnostic laboratory directors and researchers) completed three rounds of survey questions and had a face-to-face meeting.

RESULT

Panelists reviewed the initial evaluation of the screen-positive infant, diagnostic testing and management of diagnosed patients. Grade C and D consensus recommendations were made in each of these three areas. The panel did not reach consensus on all issues, particularly in the dietary management of asymptomatic infants diagnosed by newborn screening.

Commentary on a Delphi clinical practice protocol for the diagnosis and management of very long chain acyl-CoA dehydrogenase deficiency by Arnold et al

Very long chain acyl-CoA dehydrogenase deficiency (VLCAD) can now be detected by newborn screening by tandem mass spectrometry. The incidence is higher than previously estimated because of the identification of potentially milder later onset variants by screening. Although there is little information in the literature on the optimal management of rare inborn errors, there is a need for management guidelines, especially for non-specialist providers in the community. In the accompanying article, Arnold et al. present a diagnostic and management guideline for VLCAD, developed by the Delphi method for gaining consensus from a panel of 14 metabolic specialists. While consensus was gained for some issues, there was no clear consensus for several important management issues, particularly for the later onset variants. Clearly, there is an urgent need for multinational collaborative protocol driven outcomes studies that will provide the data necessary to establish robust guidelines for inborn errors of metabolism.

Liver hepatoblastoma and multiple OXPHOS deficiency in the follow-up of a patient with methylmalonic aciduria

A boy who was diagnosed with methylmalonic aciduria (MMA) at the age of 10 days developed persistent hepatomegaly and raised transaminases from the age of 4 years. He was subsequently diagnosed with Leigh syndrome and required a kidney transplantation for end-stage renal failure. A massive hepatoblastoma led to his death by the age of 11 years. Methylmalonyl-CoA mutase activity was undetectable on both cultured skin fibroblasts and kidney biopsy and multiple respiratory chain deficiency was demonstrated in the kidney. Mitochondrial dysfunction and/or post-transplant immunosuppressive therapy should be considered as a possible cause of liver cancer in this patient.

Combined liver-kidney transplant for the management of methylmalonic aciduria: a case report and review of the literature

Over 27 cases of liver transplant, kidney transplant and combined liver-kidney transplant have been reported for the treatment of methylmalonic aciduria. We describe a case of a 5-year-old boy who underwent combined liver-kidney transplant (CLKT) for phenotypic mut0 disease. His history was notable for more than 30 hospitalizations for severe acidosis, metabolic strokes, liver disease, pancreatic disease, chronic renal insufficiency with interstitial nephritis, and decreased quality of life. Post-CLKT, there was a marked reduction in serum (80%) and urine MMA levels (90%) as well as a cessation of metabolic decompensations. Neurologic deterioration continued post-CKLT manifested as a cerebellar stroke. The clinical details and therapeutic implications of solid organ transplant for methylmalonic aciduria are discussed.

Effects of a fat load and exercise on asymptomatic VLCAD deficiency

The patient was identified via family screening at the age of 3 years when very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency was diagnosed in his sister by newborn screening. Enzyme and molecular analyses confirmed VLCAD-deficiency (VLCADD). Until the age of 8 years no severe illnesses occurred and the patient was completely asymptomatic without a fat-reduced and fat-modified diet. On regular follow-up, creatine kinase (CK) and liver transaminases were always in the normal range. A long-chain fat load with 1.5 g/kg body weight did not result in clinical symptoms, nor in elevation of CK or liver transaminases. At the age of 8 years, the patient for the first time complained of recurrent muscle pain after exercise. CK concentrations were elevated up to 20,000 U/L during one of these episodes. Medium-chain fat was supplemented. With a medium-chain fat-rich meal directly before exercise, muscle pain after exercise clearly decreased. In asymptomatic mild VLCADD, a fat-reduced diet may not be necessary, whereas in later infancy and adolescence, strenuous physical exercise may require additional energy from medium-chain fat.

Very long-chain acyl-CoA dehydrogenase deficiency presenting as acute hypercapnic respiratory failure

Very long-chain acyl-CoA dehydrogenase deficiency (VLCAD) is a key enzyme catalysing the dehydrogenation of long-chain fatty acids in mitochondrial beta-oxidation. VLCAD deficiency is a genetic disorder that commonly presents in infancy or childhood with episodes of hypoketotic hypoglycaemia, cardiomyopathy and liver dysfunction. The present study reports an 18-yr-old Chinese female who presented with acute hypercapnic respiratory failure and rhabdomyolysis after a period of prolonged fasting and exertion. VLCAD deficiency was confirmed with decreased VLCAD activity in cultured fibroblasts. The patient completely recovered with supportive care. Pulmonary function tests after the acute episode showed evidence of chronic subclinical respiratory muscle weakness. In conclusion, this rare metabolic disorder should be considered in patients presenting with unexplained acute respiratory paralysis and failure.

Systemic correction of a fatty acid oxidation defect by intramuscular injection of a recombinant adeno-associated virus vector

Mitochondrial beta-oxidation of fatty acids is required to meet physiologic energy requirements during illness and periods of fasting or physiologic stress, and is most active in liver and striated muscle. Acyl-CoA dehydrogenases of varying chain-length specificities represent the first step in the mitochondria for each round of beta-oxidation, each of which removes two-carbon units as acetyl-CoA for entry into the tricarboxylic acid cycle. We have used recombinant adeno-associated virus (rAAV) vectors expressing short-chain acyl-CoA dehydrogenase (SCAD) to correct the accumulation of fatty acyl-CoA intermediates in deficient cell lines. The rAAV-SCAD vector was then packaged into either rAAV serotype 1 or 2 capsids and injected intramuscularly into SCAD-deficient mice. A systemic effect was observed as judged by restoration of circulating butyryl- carnitine levels to normal. Total lipid content at the injection site was also decreased as demonstrated by noninvasive magnetic resonance spectroscopy (MRS). SCAD enzyme activity in the injected muscle was found at necropsy to be above the normal control mouse level. This study is the first to demonstrate the systemic correction of a fatty acid oxidation disorder with rAAV and the utility of MRS as a noninvasive method to monitor SCAD correction after in vivo gene therapy.

Immunizations for patients with metabolic disorders

Individuals with underlying metabolic disorders are a potential high-risk group for vaccine-preventable diseases. Newborn metabolic screening has provided a means of early identification and treatment for many of these disorders, whereas childhood immunization is one of the most effective means of decreasing the morbidity and mortality resulting from communicable diseases worldwide. There are very few contraindications to the routine administration of vaccines to the healthy, immunocompetent individual. In certain high-risk groups, such as immunocompromised patients, gravid females, and those with a history of previous anaphylactic reaction to a vaccine or its components, selective withholding of immunizations must be considered to decrease potential adverse events. A detailed analysis of the medical literature revealed few specific recommendations regarding appropriate immunization techniques for patients with metabolic disorders. In this review we detail the major metabolic disorder subtypes, elaborate on the available literature on immunizations for patients with these disorders, and provide suggested vaccine recommendations.

Medium-chain acyl-CoA dehydrogenase deficiency: a case presentation

When an infant presents with hypoglycemia, acidosis, hepatomegaly, and respiratory arrest, the neonatal team must be alert to the possibility of a metabolic disorder. Among those to be considered is medium-chain acyl-CoA dehydrogenase deficiency, which occurs in 1 in 10,000-23,000 live births. Recognizing and treating this disorder early could decrease the morbidity and mortality associated with the diagnosis.

Mutations in lipid transporter ABCA12 in harlequin ichthyosis and functional recovery by corrective gene transfer

Harlequin ichthyosis (HI) is a devastating skin disorder with an unknown underlying cause. Abnormal keratinocyte lamellar granules (LGs) are a hallmark of HI skin. ABCA12 is a member of the ATP-binding cassette transporter family, and members of the ABCA subfamily are known to have closely related functions as lipid transporters. ABCA3 is involved in lipid secretion via LGs from alveolar type II cells, and missense mutations in ABCA12 have been reported to cause lamellar ichthyosis type 2, a milder form of ichthyosis. Therefore, we hypothesized that HI might be caused by mutations that lead to serious ABCA12 defects. We identify 5 distinct ABCA12 mutations, either in a compound heterozygous or homozygous state, in patients from 4 HI families. All the mutations resulted in truncation or deletion of highly conserved regions of ABCA12. Immunoelectron microscopy revealed that ABCA12 localized to LGs in normal epidermal keratinocytes. We confirmed that ABCA12 defects cause congested lipid secretion in cultured HI keratinocytes and succeeded in obtaining the recovery of LG lipid secretion after corrective gene transfer of ABCA12. We concluded that ABCA12 works as an epidermal keratinocyte lipid transporter and that defective ABCA12 results in a loss of the skin lipid barrier, leading to HI. Our findings not only allow DNA-based early prenatal diagnosis but also suggest the possibility of gene therapy for HI.

Mitochondrial Trifunctional Protein Defects: Molecular Basis and Novel Therapeutic Approaches

Mitochondrial trifunctional protein (MTP) is a complex protein that catalyzes the last three steps of long chain fatty acid oxidation. MTP defects have emerged recently as important inborn errors of metabolism because of their clinical implications. These disorders are recessively inherited and display a spectrum of clinical phenotypes in affected children including hepatic dysfunction, cardiomyopathy, neuro-myopathy, and may cause sudden unexpected infant death if undiagnosed and untreated. Interestingly, mothers who carry fetuses with MTP defects develop life-threatening complications during pregnancy. Recently, we delineated disease-causing mutations in MTP and reported the molecular basis for the pediatric and fetal-maternal genotype-phenotype correlations. Current management of patients with MTP defects include long-term dietary therapy of fasting avoidance, low fat diet with the restriction of long chain fatty acid intake and substitution with medium chain fatty acids. The long-term outcome of patients treated by dietary modifications remains unknown. Thus, treatment that aims at correcting the metabolic defect remains the therapy of choice for this disorder. Currently, we are exploring the potential use of protein transfection domains (PTD) for treatment of these disorders. We have shown that the transactivator of transcription (TAT) peptide from the human immunodeficiency virus can deliver proteins to mitochondria. We have further developed methods to localize these proteins to mitochondria by including a mitochondrial targeting in the fusion protein construct. Finally, we have shown that the fusion protein can cross the placenta and was detectable in the fetus and newborn pups. The practical therapeutic implications of this novel approach will be discussed.

Gene therapy of atherosclerosis

Atherosclerosis and related diseases are the leading cause of death in Western world. The disease process begins with the formation of fatty streaks already during the first decade of life but does not manifest clinically until several decades later. Gene therapy is a potential new way to target multiple factors playing a role in the development and progression of atherosclerosis. A great number of genes involved in the development of atherosclerosis have been identified and have been tested both in vitro and in vivo as potential new targets for therapy. Pre-clinical experiments have shown the feasibility and safety of several gene therapy applications for the treatment of atherosclerosis and clinical trials have also provided evidence for the applicability of gene therapy for the treatment of cardiovascular diseases. In this review we discuss vectors and potential gene therapy approaches for intervention and therapy of atherosclerosis.

The Association Between Acute Fatty Liver of Pregnancy and Fatty Acid Oxidation Disorders

Acute fatty liver of pregnancy is a relatively rare but potentially fatal liver disorder of late pregnancy. Recent advances in molecular diagnostic procedures provide evidence of a genetic basis for this condition and a link to offspring disorders in fatty acid oxidation. This relationship implies the need for genetic testing and follow-up of at-risk women and their neonates.

Steatohepatitis and unsuspected micronodular cirrhosis in Dorfman-Chanarin syndrome with documented ABHD5 mutation

Mutation in ABHD5 causes Dorfman-Chanarin syndrome (DCS), a multisystem triglyceride storage disorder. Ultrastructural study of leukocytes confirmed DCS in a child homozygous for a novel ABHD5 mutation, with ichthyosis, developmental delay, and steatohepatitis with cirrhosis, manifest only as elevated aminotranferase levels. We recommend early assessment for liver disease in DCS.

Implications of impaired ketogenesis in fatty acid oxidation disorders

Long-chain fatty acids are important sources of respiratory fuel for many tissues and during fasting the rate of hepatic production of ketone bodies is markedly increased. Many extra hepatic tissues utilize ketone bodies in the fasted state with the advantage that glucose is "spared" for more vital tissues like the brain. This glucose sparing effect of ketones is especially important in infants where there is a high proportional glucose utilization in cerebral tissue. The first reported inherited defect affecting fatty acid oxidation was described in 1973 and to date about 15 separate disorders have been described. Although individually rare, cumulatively fatty acid oxidation defects are relatively common, have major consequences for affected individuals and their families, and carry significant health care implications. The major biochemical consequence of fatty acid oxidation defects is an inability of extra hepatic tissues to utilize fatty acids as an energy source with absent or limited hepatic capacity to generate ketones. Clinically patients usually present in infancy with acute life-threatening hypoketotic hypoglycaemia, liver disease, hyperammonaemia and cerebral oedema, with or without cardiac involvement, usually following a period of catabolic stress. Chronically there may be muscle involvement with hypotonia or exercise intolerance with or without cardiomyopathy. Treatment is generally by the avoidance of fasting, frequent carbohydrate rich feeds and for long-chain defects, the replacement of long-chain dietary fats with medium-chain formulae. Novel approaches to treatment include the use of d,l-3-hydoxybutyrate or heptanoate as an alternative energy source.

Successful long-term treatment of hepatic carnitine palmitoyltransferase I deficiency and a novel mutation

Individuals with carnitine palmitoyltransferase I (CPT-I) deficiency cannot metabolize long-chain fatty acids and can develop life-threatening hypoglycaemia. We present a boy with CPT-I deficiency maintained on a very low-fat diet with nighttime uncooked cornstarch feedings for 5(1/2) years with good success. He has had normal growth and no episodes of hypoglycaemia or adverse side-effects. We found that he was homozygous for a previously undescribed mutation, T314I, in the CPT1A protein.

Hematopoietic cell transplantation for inherited metabolic diseases: an overview of outcomes and practice guidelines

For the past two decades, hematopoietic cell transplantation (HCT) has been used as effective therapy for selected inherited metabolic diseases (IMD) including Hurler (MPS IH) and Maroteaux-Lamy (MPS VI) syndromes, childhood-onset cerebral X-linked adrenoleukodystrophy (X-ALD), globoid-cell leukodystrophy (GLD), metachromatic leukodystrophy (MLD), alpha-mannosidosis, osteopetrosis, and others. Careful pre-HCT evaluation is critical and coordinated, multidisciplinary follow-up is essential in this field of transplantation. The primary goals of HCT for these disorders have been to promote long-term survival with donor-derived engraftment and to optimize the quality of life. Guidelines for HCT and monitoring are provided; a brief overview of long-term results is also presented.