Very-long-chain acyl-coenzyme A dehydrogenase deficiency in a child with recurrent myoglobinuria

Nutrition management guideline for very-long chain acyl-CoA dehydrogenase deficiency (VLCAD): An evidence- and consensus-based approach

The nutrition management guideline for very-long chain acyl-CoA dehydrogenase deficiency (VLCAD) is the fourth in a series of web-based guidelines focusing on the diet treatment for inherited metabolic disorders and follows previous publication of guidelines for maple syrup urine disease (2014), phenylketonuria (2016) and propionic acidemia (2019). The purpose of this guideline is to establish harmonization in the treatment and monitoring of individuals with VLCAD of all ages in order to improve clinical outcomes. Six research questions were identified to support guideline development on: nutrition recommendations for the healthy individual, illness management, supplementation, monitoring, physical activity and management during pregnancy. This report describes the methodology used in its development including review, critical appraisal and abstraction of peer-reviewed studies and unpublished practice literature; expert input through two Delphi surveys and a nominal group process; and external review from metabolic physicians and dietitians. It includes the summary statements of the nutrition management recommendations for each research question, followed by a standardized rating based on the strength of the evidence. 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 VLCAD and their families and can be accessed from the Genetic Metabolic Dietitians International (https://GMDI.org) and Southeast Regional Genetics Network (https://southeastgenetics.org/ngp) websites.

Rhabdomyolysis in a neonate due to very long chain acyl CoA dehydrogenase deficiency

Very long chain acyl CoA dehydrogenase deficiency (VLCADD) is an inborn error in long chain fatty acid oxidation with significant variability in the severity and timing of its clinical presentation. Neonatal presentations of VLCADD have included hypoglycemia and cardiomyopathy while rhabdomyolysis is usually a later onset complication. We describe a neonate with VLCADD presenting with rhabdomyolysis prior to the return of an abnormal newborn screen. This report suggests that evaluating for rhabdomyolysis, in addition to a cardiac and hepatic work-up, is an important part of the initial evaluation of an infant with an abnormal newborn screen suggesting a diagnosis of VLCADD.

Inborn errors of energy metabolism associated with myopathies

Inherited neuromuscular disorders affect approximately one in 3,500 children. Structural muscular defects are most common; however functional impairment of skeletal and cardiac muscle in both children and adults may be caused by inborn errors of energy metabolism as well. Patients suffering from metabolic myopathies due to compromised energy metabolism may present with exercise intolerance, muscle pain, reversible or progressive muscle weakness, and myoglobinuria. In this review, the physiology of energy metabolism in muscle is described, followed by the presentation of distinct disorders affecting skeletal and cardiac muscle: glycogen storage diseases types III, V, VII, fatty acid oxidation defects, and respiratory chain defects (i.e., mitochondriopathies). The diagnostic work-up and therapeutic options in these disorders are discussed.

Diagnostic assessment and long-term follow-up of 13 patients with Very Long-Chain Acyl-Coenzyme A dehydrogenase (VLCAD) deficiency

Very Long-Chain Acyl-CoA dehydrogenase (VLCAD) deficiency is an inborn error of mitochondrial long-chain fatty acid oxidation (FAO) most often occurring in childhood with cardiac or liver involvement, but rhabdomyolysis attacks have also been reported in adults. We report in this study the clinical, biochemical and molecular studies in 13 adult patients from 10 different families with VLCAD deficiency. The enzyme defect was demonstrated in cultured skin fibroblasts or lymphocytes. All patients exhibited exercise intolerance and recurrent rhabdomyolysis episodes, which were generally triggered by strenuous exercise, fasting, cold or fever (mean age at onset: 10 years). Inaugural life-threatening general manifestations also occurred before the age of 3 years in four patients. Increased levels of long-chain acylcarnitines with tetradecenoylcarnitine (C14:1) as the most prominent species were observed in all patients. Muscle biopsies showed a mild lipidosis in four patients. For all patients but two, molecular analysis showed homozygous (4 patients) or compound heterozygous genotype (7 patients). For the two remaining patients, only one mutation in a heterozygous state was detected. This study confirms that VLCAD deficiency, although being less frequent than CPT II deficiency, should be systematically considered in the differential diagnosis of exercise-induced rhabdomyolysis. Measurement of fasting blood acylcarnitines by tandem mass spectrometry allows accurate biochemical diagnosis and should therefore be performed in all patients presenting with unexplained muscle exercise intolerance or rhabdomyolysis.

Fuel utilization in patients with very long-chain acyl-coa dehydrogenase deficiency

Fuel utilization in two adult patients with the myopathic form of very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency and five healthy subjects was investigated with stable isotopes during exercise at 50% of VO2max. The findings indicate that residual VLCAD activity in the patients is sufficient to maintain normal oxidation of fat at rest, but that fat oxidation rate cannot increase above basal levels during exercise. This can cause an energy deficit and intramuscular accumulation of fat intermediates that may induce the exercise-induced symptoms.

Myopathic form of very-long chain acyl-coa dehydrogenase deficiency: evidence for temperature-sensitive mild mutations in both mutant alleles in a Japanese girl

In a 14-year-old Japanese girl, manifested recurrent myalgia with elevated serum creatine kinase after moderate exercise became evident, and she was diagnosed as having a myopathic form of very-long chain acyl-CoA dehydrogenase deficiency. Her first clinical symptom of the disease was evident when she was 6 y of age. She had never had hypoglycemic attacks, and hepatomegaly and cardiomyopathy were absent. The diagnosis was suspected on the basis of the urinary organic acid profile after a 36-h fast, long-chain fatty acid-loading test, and the blood acylcarnitine profile. Acyl-CoA dehydrogenase activity with palmitoyl-CoA as a substrate was severely decreased in her fibroblasts, and the amount of very-long chain acyl-CoA dehydrogenase protein was reduced. She was a compound heterozygote of A416T from her father and R450H from her mother. Transient expression of mutant A416T cDNA retained a significant residual acyl-CoA dehydrogenase activity of 10% and 20% normal at 37 degrees C and 30 degrees C, respectively. Specific activity of A416T mutant protein was calculated to be one fifth that of control. In the case of R450H mutant expression, a low residual acyl-CoA dehydrogenase activity of 5% normal was detected at 30 degrees C although significant activity was absent at 37 degrees C. The R450H protein was not detected at 37 degrees C but was clearly detected at one fourth the normal amount at 30 degrees C. These results indicate that both mutations were temperature-sensitive mild mutations, the result being the mildest phenotype of very-long chain acyl-CoA dehydrogenase deficiency.

Isolated loss of ?-sarcoglycan: Diagnostic implications in autosomal recessive limb-girdle muscular dystrophies

Mutations in the sarcoglycan (SG) genes cause a subset of limb-girdle muscular dystrophies (LGMD). We report a Spanish patient with progressive LGMD exhibiting an almost isolated loss of gamma-SG and a homozygous Delta521-T mutation in the gamma-SG gene. These results suggest that isolated loss of gamma-SG might remain undetected using only the alpha-SG antibody in routine muscle biopsy studies. Both alpha- and gamma-SG antibodies should be used in the diagnostic detection of patients with LGMD.

Myoglobinuria

Myoglobinuria refers to an abnormal pathologic state in which an excessive amount of myoglobin is found in the urine, imparting a cola-like hue, usually in association with myonecrosis and a clinical picture of weakness, myalgias, and edema. Myoglobinuria is produced by multiple causes: any condition that accelerates the use or interferes with the availability of oxygen or energy substrates to muscle cells can result in myoglobinuria, as can events that produce direct muscle injury, either mechanical or chemical. Acute renal failure is the most serious complication, which can be prevented by prompt, aggressive treatment. In patients surviving acute attacks, recovery of muscle and renal function is usually complete.

Clinical and molecular heterogeneity in very-long-chain acyl-coenzyme A dehydrogenase deficiency

Very-long-chain acyl-coenzyme A dehydrogenase (VLCAD) deficiency is an increasingly recognized defect of mitochondrial fatty acid beta-oxidation manifesting with episodes of metabolic decompensation or isolated recurrent myoglobinuria. In this report the clinical, biochemical, and molecular studies in a series of five patients (four Italian and one Spanish) with this disorder are discussed. Biochemical studies included the determination of fibroblast substrate oxidation rates and enzyme activity and Western blot analysis of VLCAD protein. Molecular analysis was performed by sequencing the VLCAD gene from the genomic DNA. Clinical features were within the spectrum previously reported. Four patients presented in infancy or childhood with episodes of severe metabolic decompensation and dicarboxylic aciduria. Two exhibited cardiomyopathy. The fifth patient presented with isolated recurrent rhabdomyolysis, with no cardiomyopathy or dicarboxylic aciduria. In all patients a significant loss of VLCAD activity associated with a marked reduction of VLCAD protein levels occurred. Molecular analysis disclosed one novel missense mutation (Cys437Tyr) and four previously reported mutations, including two missense substitutions (Phe418Leu and Arg419Trp), a single amino acid deletion (Lys258del), and one splice site mutation (IVS8-C(-2)), which was present in all four Italian patients. All patients exhibited compound heterozygosity. The phenotypic variability and the high genotypic heterogeneity of this hereditary metabolic disorder is reported.

Identification of two novel mutations in the hypoglycemic phenotype of very long chain acyl-CoA dehydrogenase deficiency

Very long chain acyl-CoA dehydrogenase (VLCAD) catalyzes the initial step of long chain fatty acid oxidation in the mitochondria. Patients with VLCAD deficiency have recently been observed with two clinical phenotypes. The cardiac form presents with an early onset cardiomyopathy and a high incidence of infant death, while the hypoglycemic form resembles medium chain acyl-CoA dehydrogenase (MCAD) manifesting with hypoketotic hypoglycemia. In our investigation on the molecular basis for these phenotypes, we identified two novel mutations in one VLCAD patient with the hypoglycemic form, a C953T (Pro318Leu) mutation in exon 10 resulting in a substitution of proline 318 by leucine on one allele, and a C1194A (Tyr398Stop) mutation in exon 12 which created a premature stop codon TAA on another allele. The Tyr398Stop mutation may result in a truncated protein or instable messenger RNA.

Adolescent myopathic presentation in two sisters with very long-chain acyl-CoA dehydrogenase deficiency

Two sisters were investigated at the ages of 20 and 13 years owing to persistently increased serum creatine kinase and recurrent episodes of rhabdomyolysis after emotional stress in the older and myalgias in the younger. The finding of increased levels of cis-5-tetradecenoic acid (C14:1) in plasma, severe hypocarnitinaemia and the absence of a pathological dicarboxylic aciduria in both sisters suggested a very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency. Reduced [1-(14)C]palmitate oxidation and deficient mitochondrial VLCAD activity in fibroblasts were found. Mutation analysis revealed compound heterozygosity for Asp365His and Arg410His changes. This late-onset, milder clinical presentation differs from the other two more severe infantile phenotypes described, since there is no hypoglycaemia or cardiac disease. Fatty acid oxidation defects should be investigated in all cases with rhabdomyolysis beginning in adolescence or early adulthood.

Very long chain acyl coenzyme A dehydrogenase deficiency in a 5-month-old Korean boy: identification of a novel mutation

A 5-month-old Korean boy who presented with lethargy and cardiomyopathy was diagnosed with very long chain acyl coenzyme A dehydrogenase (VLCAD) deficiency by organic acid, fatty acid, acylcarnitine, and molecular genetic analysis. The patient was a compound heterozygote for mutations in the VLCAD gene. One allele contains a 3-bp deletion in exon 6, deleting glutamic acid in codon 130 (E130del ); this allele is of paternal origin. The patient's maternally derived allele is a novel mutation, C1843T in exon 20, which creates a premature termination codon (R615stop ). Although molecular genetic characterization of VLCAD deficiency is limited to a few patients, heterogeneity of mutations is already apparent. However, the E130del is a relatively frequent mutant allele, which has been noted in 2 previously identified patients. The 2 mutant alleles in our patient appear to be responsible for his severe and fatal clinical manifestations.

Myopathy in very-long-chain acyl-CoA dehydrogenase deficiency: clinical and biochemical differences with the fatal cardiac phenotype

A 30-year-old man suffered since the age of 13 years from exercise induced episodes of intense generalised muscle pain, weakness and myoglobinuria. Fasting ketogenesis was low, while blood glucose remained normal. Muscle mitochondria failed to oxidise palmitoylcarnitine. Palmitoyl-CoA dehydrogenase was deficient in muscle and fibroblasts, consistent with deficiency of very-long-chain acyl-CoA dehydrogenase (VLCAD). The gene of this enzyme had a homozygous deletion of three base pairs in exon 9, skipping lysine residue 238. Fibroblasts oxidised myristate, palmitate and oleate at a rate of 129, 62 and 38% of controls. In contrast to patients with cardiac VLCAD deficiency, our patient had no lipid storage, a normal heart function, a higher rate of oleate oxidation in fibroblasts and normal free carnitine in plasma and fibroblasts. 31P-nuclear magnetic resonance spectroscopy of muscle showed a normal oxidative phosphorylation as assessed by phosphocreatine recovery, but a significant increase in pH and in Pi/ATP ratio.

Clear correlation of genotype with disease phenotype in very-long-chain acyl-CoA dehydrogenase deficiency

Very-long-chain acyl-CoA dehydrogenase (VLCAD) catalyzes the initial rate-limiting step in mitochondrial fatty acid beta-oxidation. VLCAD deficiency is clinically heterogenous, with three major phenotypes: a severe childhood form, with early onset, high mortality, and high incidence of cardiomyopathy; a milder childhood form, with later onset, usually with hypoketotic hypoglycemia as the main presenting feature, low mortality, and rare cardiomyopathy; and an adult form, with isolated skeletal muscle involvement, rhabdomyolysis, and myoglobinuria, usually triggered by exercise or fasting. To examine whether these different phenotypes are due to differences in the VLCAD genotype, we investigated 58 different mutations in 55 unrelated patients representing all known clinical phenotypes and correlated the mutation type with the clinical phenotype. Our results show a clear relationship between the nature of the mutation and the severity of disease. Patients with the severe childhood phenotype have mutations that result in no residual enzyme activity, whereas patients with the milder childhood and adult phenotypes have mutations that may result in residual enzyme activity. This clear genotype-phenotype relationship is in sharp contrast to what has been observed in medium-chain acyl-CoA dehydrogenase deficiency, in which no correlation between genotype and phenotype can be established.