J. L. K. Van Hove

Clinical and metabolic correction of pompe disease by enzyme therapy in acid maltase-deficient quail.

Pompe disease is a fatal genetic muscle disorder caused by a deficiency of acid alpha-glucosidase (GAA), a glycogen degrading lysosomal enzyme. GAA-deficient (AMD) Japanese quails exhibit progressive myopathy and cannot lift their wings, fly, or right themselves from the supine position (flip test). Six 4-wk-old acid maltase-deficient quails, with the clinical symptoms listed, were intravenously injected with 14 or 4.2 mg/kg of precursor form of recombinant human GAA or buffer alone every 2-3 d for 18 d (seven injections). On day 18, both high dose-treated birds (14 mg/kg) scored positive flip tests and flapped their wings, and one bird flew up more than 100 cm. GAA activity increased in most of the tissues examined. In heart and liver, glycogen levels dropped to normal and histopathology was normal. In pectoralis muscle, morphology was essentially normal, except for increased glycogen granules. In sharp contrast, sham-treated quail muscle had markedly increased glycogen granules, multi-vesicular autophagosomes, and inter- and intrafascicular fatty infiltrations. Low dose-treated birds (4.2 mg/kg) improved less biochemically and histopathologically than high dose birds, indicating a dose-dependent response. Additional experiment with intermediate doses and extended treatment (four birds, 5.7-9 mg/kg for 45 d) halted the progression of the disease. Our data is the first to show that an exogenous protein can target to muscle and produce muscle improvement. These data also suggest enzyme replacement with recombinant human GAA is a promising therapy for human Pompe disease.

Idebenone treatment in Friedreich's ataxia: neurological, cardiac, and biochemical monitoring

The authors report 1-year prospective data on eight patients with Friedreich ataxia. Idebenone did not halt the progression of ataxia. At the end of therapy, cardiac ultrasound demonstrated significant reduction of cardiac hypertrophy in six of eight patients. Cardiac strain and strain rate imaging showed that the reduction of hypertrophy is preceded by an early and linear improvement in cardiac function. Idebenone reduced erythrocyte protoporphyrin IX levels in five of six patients with elevated baseline levels; however, changes did not consistently relate to cardiac improvement.

MRI of the brain and cervical spinal cord in rhizomelic chondrodysplasia punctata

Background: The classic rhizomelic chondrodysplasia punctata (RCDP) phenotype involves a typical facial appearance, cataracts, skeletal dysplasia causing disproportionate somatic growth failure, microcephaly, and severe psychomotor defects. Biochemical abnormalities include impaired plasmalogen biosynthesis in all forms of RCDP and accumulation of phytanic acid in RCDP type 1. A subset of patients has a milder clinical and biochemical phenotype, with less severe neurologic impairment and an incomplete deficiency in plasmalogens. The impact of plasmalogen deficiency on neurologic function is severe, causing spasticity and mental defects, but its pathomechanism is still unknown. The authors specifically focused on myelination because myelin is rich in ethanolamine plasmalogens. Objective: To define the neuroimaging characteristics of the genetic peroxisomal disorder RCDP. Methods: Twenty-one MR images of the brain and cervical spine of 11 patients were evaluated and correlated with neurologic and biochemical profiles. Results: No abnormalities on MRI were seen in the patients with a mild phenotype of RCDP, whereas delayed myelination, ventricular enlargement and increased subarachnoidal spaces, supratentorial myelin abnormalities, and cerebellar atrophy were observed in patients with the severe phenotype of both RCDP type 1 and 3. The severity of both the MRI abnormalities and the clinical phenotype is correlated with the plasmalogen level. Conclusions: The severe phenotype of rhizomelic chondrodysplasia punctata (RCDP) is accompanied by a specific pattern of both developmental and regressive MRI abnormalities. Plasmalogen levels seem to play an important role in the pathophysiology of CNS abnormalities in RCDP. Increased phytanic acid appears not to be the cause of cerebellar atrophy.

Clinical and biochemical characteristics of congenital disorder of glycosylation type Ic, the first recognized endoplasmic reticulum defect in N-glycan synthesis

We report on 8 patients with a recently described novel subtype of congenital disorder of glycosylation type Ic (CDG‐Ic). Their clinical presentation was mainly neurological with developmental retardation, muscular hypotonia, and epilepsy. Several symptoms commonly seen in CDG‐Ia such as inverted nipples, abnormal fat distribution, and cerebellar hypoplasia were not observed. The clinical course is milder overall, with a better neurological outcome, than in CDG‐Ia. The isoelectric focusing pattern of serum transferrin in CDG‐Ia and CDG‐Ic is indistinguishable. Interestingly, β‐trace protein in cerebrospinal fluid derived from immunoblot analysis of the brain showed a less pronounced hypoglycosylation pattern in CDG‐Ic patients than in CDG‐Ia patients. Analysis of lipid‐linked oligosaccharides revealed an accumulation of Man9GlcNAc2 intermediates due to dolichol pyrophosphate–Man9GlcNAc2 α‐1,3 glucosyltransferase deficiency. All patients were homozygous for an A333V mutation. Ann Neurol 2000;47:776–781

Acylcarnitines in fibroblasts of patients with long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency and other fatty acid oxidation disorders

Mitochondrial fatty acid oxidation disorders cause hypoglycaemia, hepatic dysfunction, myopathy, cardiomyopathy and encephalopathy. Despite their recognition for more than 15 years, diagnosis and treatment remain difficult. To help design rational diagnostic and therapeutic strategies, we studied the pathophysiology of accumulating metabolites in a whole-cell system. Acylcarnitines were quantified in cells and media of cultured fibroblasts after incubation with L-carnitine and fatty acids. Following incubation with palmitate, long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD)-deficient fibroblasts compared with controls showed elevation of hydroxypalmitoyl- and palmitoylcarnitine and reduction of C10- and shorter acylcarnitines, and following incubation with linoleate an increase in C14:2-, C18:2- and hydroxy-C18:2-acylcarnitines and reduction in C10:1-acylcarnitines. Hydroxyacylcarnitines remained more intracellular compared to corresponding saturated acylcarnitines. Incubation with decanoate and octanoate showed absence of hydroxylated acylcarnitines and correction of secondary metabolic disturbances, suggesting that optimal treatment should include medium-chain triglycerides of these chain lengths. Fibroblasts of patients with other fatty acid oxidation disorders showed distinct elevations of disease-specific acylcarnitines. This acylcarnitine analysis allows the diagnosis of LCHAD deficiency and its differentiation from other fatty acid oxidation disorders, which can pose difficulties in vivo. The strategy has allowed in-depth analysis with different substrates, providing suggestions for the rational design of treatment trials.

Benzoate treatment and the glycine index in nonketotic hyperglycinaemia.

SummaryHigh-dose benzoate treatment aimed at reducing plasma glycine levels to normal reduces seizures and increases wakefulness in patients with nonketotic hyperglycinaemia (NKH). Since benzoate metabolism is dependent on the available glycine pool, and since the glycine pool is variably affected by the deficiency in the glycine cleavage enzyme system, we examined the importance of interpatient variability in benzoate requirement. To correct for the dietary glycine contribution, the glycine index was introduced as the molar requirement of benzoate dose necessary to normalize plasma glycine levels and subtracting from that the dietary glycine intake, both corrected for weight. The glycine index varied between 3.62 and 4.87 mmol/kg per day in five patients with a poor neurodevelopmental outcome and between 0.92 and 1.90 mmol/kg per day in four patients with a better neurodevelopmental outcome, and was 2.54 mmol/kg per day in a single patient with an intermediate outcome. The glycine index was stable over time within each patient. Exceeding the balance by either increasing food glycine intake or decreasing the benzoate dose resulted in increased glycine levels. Exceeding the glycine tolerance by increasing benzoate resulted in elevated and toxic levels of benzoate. The glycine index is a stable, individually specific parameter in patients with NKH. It has clinical consequences for the dose of benzoate required and the role of dietary management. Through its correlation with neurodevelopmental outcome, the glycine index points to potential genetic factors that could contribute to the psychomotor retardation in NKH.

Acute pancreatitis in an infant with lactic acidosis and a mutation at nucleotide 3243 in the mitochondrial DNA tRNALeu[UUR] gene

The A to G point mutation at position 3243 of the mitochondrial DNA tRNALeu(UUR)gene is commonly found in patients with the syndrome of mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS). A male patient was referred at 7 months with failure to thrive, developmental delay, microcephaly and hypotonia since age 2 months. He had developed lactic acidosis and increasingly frequent seizures since age 5 months. The patient was admitted at 15 months with pleural and pericardial effusions, which resolved. Three weeks later he developed evidence of pancreatitis with hyperglycemia, sudden profound increase in lactic acidosis and increased serum lipase. He died unexpectedly the next day of cardiorespiratory collapse following an acute gastro-intestinal hemorrhage. Analysis of mitochondrial DNA (mtDNA) in muscle showed heteroplasmy for the mutation MTTL1*MELAS3243G (> 95%). Infants with this mutation commonly present with failure to thrive, significant developmental delay, and hypotonia, while stroke-like episodes occur later in survivors. They usually have lactic acidosis and a high percentage of mutant mtDNA in muscle.

3-Hydroxyisovalerylcarnitine in 3-methylcrotonyl-CoA carboxylase deficiency

SummaryA new acylcarnitine was observed in the plasma and urine of a patient with isolated 3-methylcrotonyl-CoA carboxylase deficiency. Analysis by tandem mass spectrometry of the methyl ester and butyl ester and their fragment ion spectra identified it as a 3-hydroxy-C5-acylcarnitine. Fibroblasts from a second patient were incubated with deuterium-labelled leucine. Incorporation of label in the new acylcarnitine identified its origin from leucine, and thus confirmed the structure as 3-hydroxyisovalerylcarnitine. The presence of elevated amounts of this metabolite, plus a small amount of 3-methylcrotonylcarnitine in plasma, was diagnostic for isolated 3-methylcrotonyl-CoA carboxylase deficiency. Other conditions in which a hydroxy-C5-acylcarnitine was present were readily differentiated by the abnormal elevation of other acylcarnitines.

Acute hydrocephalus in nonketotic hyperglycinemia

Article abstract We present four patients with typical neonatal onset nonketotic hyperglycinemia (NKH) who developed hydrocephalus requiring shunting in early infancy. Brain imaging revealed acute hydrocephalus, a megacisterna magna or posterior fossa cyst, pronounced atrophy of the white matter, and an extremely thin corpus callosum in all. The three older patients had profound developmental disabilities. This suggests that the development of hydrocephalus in NKH is an additional poor prognostic sign.

Acylcarnitines in plasma and blood spots of patients with long-chain 3-hydroxyacyl-coenzyme A dehydrogenase defiency

The acylcarnitines in plasma and blood spots of 23 patients with proven deficiency of long-chain 3-hydroxyacylcoenzyme A dehydrogenase were reviewed. Long-chain 3-hydroxyacylcarnitines of C14:1, C14, C16 and C18:1 chain length, and long-chain acylcarnitines of C12, C14:1, C14, C16, C18:2 and C18:1 chain length were elevated. Acetylcarnitine was decreased. In plasma, elevation of hydroxy-C18:1 acylcarnitine over the 95th centile of controls, in combination with an elevation of two of the three acylcarnitines C14, C14:1 and hydroxy-C16, identified over 85% of patients with high specificity (less than 0.1% false positive rate). High endogenous levels of long-chain acylcarnitines in normal erythrocytes reduced the diagnostic specificity in blood spots compared with plasma samples. The results were also diagnostic in asymptomatic patients, and were not influenced by genotype. Treatment with diet low in fat and high in medium-chain triglyceride decreased all disease-specific acylcarnitines, often to normal, suggesting that this assay is useful in treatment monitoring.