Expanded motor and psychiatric phenotype in autosomal dominant Segawa syndrome due to GTP cyclohydrolase deficiency.

BACKGROUND: Segawa syndrome due to GTP cyclohydrolase deficiency is an autosomal dominant disorder with variable expression, that is clinically characterised by l-dopa responsive, diurnally fluctuating dystonia and parkinsonian symptoms. OBJECTIVE: To delineate the neurological and psychiatric phenotype in all affected individuals of three extended families. METHODS: GTP cyclohydrolase deficiency was documented by biochemical analyses, enzymatic measurements in fibroblasts, and molecular investigations. All affected individuals were examined neurologically, and psychiatric data were systematically reviewed. RESULTS: Eighteen affected patients from three families with proven GTP cyclohydrolase deficiency were identified. Eight patients presenting at less than 20 years of age had typical motor symptoms of dystonia with diurnal variation. Five family members had late-presenting mild dopa-responsive symptoms of rigidity, frequent falls, and tendonitis. Among mutation carriers older than 20 years of age, major depressive disorder, often recurrent, and obsessive-compulsive disorder were strikingly more frequent than observed in the general population. Patients responded well to medication increasing serotonergic neurotransmission and to l-dopa substitution. Sleep disorders including difficulty in sleep onset and maintenance, excessive sleepiness, and frequent disturbing nightmares were present in 55% of patients. CONCLUSION: Physicians should be aware of this expanded phenotype in affected members of families with GTP cyclohydrolase deficiency.

Benzoate treatment and the glycine index in nonketotic hyperglycinaemia.

High-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.

Natural history of nonketotic hyperglycinemia in 65 patients.

BACKGROUND: Glycine encephalopathy, also known as nonketotic hyperglycinemia (NKH), is an autosomal recessive disorder caused by a defect in the glycine cleavage system. NKH is classically associated with neonatal apnea, lethargy, hypotonia, and seizures, followed by severe psychomotor retardation in those who survive. METHODS: To determine the natural history of NKH, the authors mailed a 44-question survey to 170 households in the International NKH Family Network. RESULTS: Data for 65 patients (36 boys, 29 girls) were collected from 58 families. One-third of the subjects died; 8 girls died during the neonatal period, and 14 patients died thereafter (2 girls, 12 boys). Median age of death for boys was 2.6 years vs <1 month for girls (p = 0.02). Mean birth weight and length, occipitofrontal circumference, and gestation duration were normal. Two-thirds of infants were ventilated during the neonatal period; of these, 40% died. Ninety percent had confirmed seizures, 75% during the first month of life. Interestingly, three NKH patients never developed seizures. An abnormal corpus callosum and/or hydrocephalus were associated with especially poor gross motor and speech development. Of 25 patients living > or =3 years, 10 were able to walk and say/sign words; all were boys. In six families with more than one affected child, disease course and mortality were similar within each family. CONCLUSIONS: This study reveals a striking and unexpected gender difference in mortality and developmental progress. Of the two-thirds of nonketotic hyperglycinemia patients surviving the newborn period, up to 20% (mostly boys) may learn to walk and communicate by saying or signing words.

Neuroleptic malignant syndrome in juvenile neuronal ceroid lipofuscinosis associated with low-dose risperidone therapy.

We present a patient with juvenile neuronal ceroid lipofuscinosis who developed a neuroleptic malignant syndrome when treated for hallucinations with a very low dose of risperidone, an atypical neuroleptic medication with usually few extrapyramidal side-effects. The loss of dopaminergic neurons in this condition may make these patients more vulnerable to this severe adverse effect.

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.

Ophthalmological findings in a patient with mucolipidosis III (pseudo-hurler polydystrophy). A case report.

Mucolipidosis III (Pseudo-Hurler Polydystrophy) is a rare autosomal recessively inherited Hurler-like disease. The ophthalmological findings in these patients include a triad of mild retinopathy, corneal clouding and hyperopic astigmatism. We present a patient with these ophthalmological characteristics.

Molybdopterin synthase mutations in a mild case of molybdenum cofactor deficiency.

Molybdenum cofactor deficiency is a rare inborn error of metabolism with generally severe symptoms, most often including neonatal seizures and severe developmental delay. We describe a patient with an unusually mild form of the disease. Two mutations in MOCS2A (molybdenum cofactor synthesis enzyme 2A) were identified: a single base change, 16C > T, that predicts a Q6X substitution on one allele and a 19G > T transversion that predicts a valine to phenylalanine substitution, V7F, on the second. It is postulated that the milder clinical symptoms result from a low level of residual molybdopterin synthase activity derived from the 19G > T allele.

The mutational spectrum of human malignant autosomal recessive osteopetrosis.

Human malignant infantile osteopetrosis (arOP; MIM 259700) is a genetically heterogeneous autosomal recessive disorder of bone metabolism, which, if untreated, has a fatal outcome. Our group, as well as others, have recently identified mutations in the ATP6i (TCIRG1) gene, encoding the a3 subunit of the vacuolar proton pump, which mediates the acidification of the bone/osteoclast interface, are responsible for a subset of this condition. By sequencing the ATP6i gene in arOP patients from 44 unrelated families with a worldwide distribution we have now established that ATP6i mutations are responsible for approximately 50% of patients affected by this disease. The vast majority of these mutations (40 out of 42 alleles, including seven deletions, two insertions, 10 nonsense substitutions and 21 mutations in splice sites) are predicted to cause severe abnormalities in the protein product and are likely to represent null alleles. In addition, we have also analysed nine unrelated arOP patients from Costa Rica, where this disease is apparently much more frequent than elsewhere. All nine Costa Rican patients bore either or both of two missense mutations (G405R and R444L) in amino acid residues which are evolutionarily conserved from yeast to humans. The identification of ATP6i gene mutations in two families allowed us for the first time to perform prenatal diagnosis: both fetuses were predicted not to be affected and two healthy babies were born. This study contributes to the determination of genetic heterogeneity of arOP and allows further delineation of the other genetic defects causing this severe condition.

Liquid chromatographic assay for a glucose tetrasaccharide, a putative biomarker for the diagnosis of Pompe disease.

A HPLC method associated with butyl-p-aminobenzoate derivatization has been developed for the analysis of a tetraglucose oligomer, Glcalpha1-6Glcalpha1-4Glcalpha1-4Glc, designated Glc(4), in biological fluids. This tetraglucose, normally excreted in the urine, has previously been shown to be elevated in a number of pathological conditions including Pompe disease (glycogen storage disease type II), which is caused by a deficiency of the lysosomal enzyme acid alpha-glucosidase. Concentrations of Glc(4) in both urine and plasma were established for the age ranges of <1, 1-5, 6-10, 11-20, and >20 years, both in normal individuals and in a cohort of 21 patients with enzymatically confirmed Pompe disease. The Glc(4) concentration decreased with age in both groups, but all the patients had elevated Glc(4) levels compared with age-matched controls. Electrospray tandem mass spectrometry was employed to establish the homogeneity of the HPLC peak for Glc(4) and to investigate the identity of other unusual oligosaccharides excreted in patient urine. Our results demonstrate that this method is suitable for application in clinical laboratories to help establish the diagnosis of Pompe disease.

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.

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, beta-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 alpha-1,3 glucosyltransferase deficiency. All patients were homozygous for an A333V mutation.

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 palmitoyl-carnitine 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.

Acute hydrocephalus in nonketotic hyperglycinemia.

We present four patients with typical neonatal onset non-ketotic 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.

Treatment of pyruvate carboxylase deficiency with high doses of citrate and aspartate.

A patient with severe pyruvate carboxylase deficiency presented at age 11 weeks with metabolic decompensation after routine immunization. She was comatose, had severe lactic acidemia (22 mM) and ketosis, low aspartate and glutamate, elevated citrulline and proline, and mild hyperammonemia. Head magnetic resonance imaging showed subdural hematomas and mild generalized brain atrophy. Biotin-unresponsive pyruvate carboxylase deficiency was diagnosed. To provide oxaloacetate, she was treated with high-dose citrate (7.5 mol/kg(-1)/day(-1)), aspartate (10 mmol/kg(-1)/day(-1)), and continuous drip feeding. Lactate and ketones diminished dramatically, and plasma amino acids normalized, except for arginine, which required supplementation. In the cerebrospinal fluid (CSF), glutamine remained low and lysine elevated, showing the treatment had not normalized brain chemistry. Metabolic decompensations, triggered by infections or fasting, diminished after the first year. They were characterized by severe lactic and ketoacidosis, hypernatremia, and a tendency to hypoglycemia. At age 3(1/2) years she has profound mental retardation, spasticity, and grand mal and myoclonic seizures only partially controlled by anticonvulsants. The new treatment regimen has helped maintain metabolic control, but the neurological outcome is still poor.

One-methyl group metabolism in non-ketotic hyperglycinaemia: mildly elevated cerebrospinal fluid homocysteine levels.

Non-ketotic hyperglycinaemia (NKH) is a rare, severe brain disease caused by deficient glycine cleavage enzyme complex activity resulting in elevated glycine concentrations. Recent experience suggests that factors in addition to glycine kinetics are involved in its pathogenesis. The glycine cleavage reaction through the formation of methylenetetrahydrofolate is an important one-methyl group donor. A deficiency in one-methyl group metabolites, in particular of choline, has been hypothesized in NKH. We investigated metabolites involved in one-methyl group metabolism in plasma and CSF of 8 patients with NKH, and monitored the effect of treatment with choline in one patient. Plasma and CSF choline and phosphatidylcholine concentrations were normal, except for a low plasma choline in the single neonate studied. Choline treatment did not change brain choline content, and was not associated with clinical or radiological improvement. Methionine concentrations and, in one-patient, S-adenosylmethionine and 5-methyltetrahydrofolate concentrations were normal in CSF. Homocysteine concentrations in CSF, however, were slightly but consistently elevated in all four patients examined, but cysteine, cysteinylglycine and glutathione were normal. Serine is important in the transfer of one-methyl groups from mitochondria to cytosol. Serine concentrations were normal in plasma and CSF, but dropped to below normal in CSF in three patients on benzoate treatment. These observations add to our understanding of the complex metabolic disturbances in NKH.

Recombinant human acid alpha-glucosidase corrects acid alpha-glucosidase-deficient human fibroblasts, quail fibroblasts, and quail myoblasts.

Acid alpha-glucosidase (GAA) deficiency causes Pompe disease, a lethal lysosomal glycogen storage disease for which no effective treatment currently exists. We investigated the endocytic process in deficient cells of human recombinant GAA produced in Chinese hamster ovary cells, and the potential of GAA-deficient Japanese acid maltase-deficient quail as a model for evaluating the enzyme replacement therapy for Pompe disease. After 24-h incubation with a single dose of recombinant enzyme, intracellular GAA and glycogen levels in deficient human fibroblasts were normalized, and this correction lasted for 7 d. The 110-kD precursor recombinant enzyme was processed to the 76-kD mature form within 24 h after uptake. Intracellular GAA levels in deficient quail fibroblasts and myoblasts were similarly corrected to their average normal levels within 24 h. Differences existed in the efficiency of endocytosis among subfractions of the enzyme, and among different cell types. Fractions with a larger proportion of precursor GAA were endocytosed more efficiently. Quail fibroblasts required a higher dose, 4200 nmol.h-1.mL-1 to normalize intracellular GAA levels than human fibroblasts, 1290 nmol.h-1.mL-1, whereas primary quail myoblasts required 2800 nmol.h-1.mL-1. In all three cell lines, the endocytosed enzyme localized to the lysosomes on immunofluorescence staining, and the endocytosis was inhibited by mannose 6-phosphate (Man-6-P) added to the culture medium. Despite structural differences in Man-6-P receptors between birds and mammals, these studies illustrate that Man-6-P receptor mediated endocytosis is present in quail muscle cells, and demonstrate the potential of acid maltase-deficient quail to test receptor mediated enzyme replacement therapy for Pompe disease.

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.

[Treatment of Pompe's disease with recombinant enzymes]. / Behandeling van de ziekte van Pompe met recombinant enzym.

Pompe disease is caused by the congenital deficiency of the lysosomal enzyme acid alpha-glucosidase. The accumulation of lysosomal glycogen results in a fatal myopathy and cardiomyopathy. We developed an enzyme replacement therapy based on recombinant human acid alpha-glucosidase enzyme targeted to the organs of interest by the presence of mannose-6-phosphate on this precursor enzyme and a manose-6-phosphate receptor present in muscle and heart. Using molecular techniques and following extensive selection, Chinese hamster ovary cells were developed that produced very large quantities of precursor human acid alpha-glucosidase in the culture medium. An improved method of purification of this precursor enzyme from tissue culture medium was developed. This purified precursor enzyme was taken up efficiently by patient's fibroblasts, and corrected with a single dose the lysosomal glycogen accumulation for one week. Finally, intravenous administration of the recombinant enzyme corrected the pathology and symptoms of an animal model of this disorder, the acid alpha-glucosidase deficient Japanese quail.

Rapid diagnosis of MCAD deficiency: quantitative analysis of octanoylcarnitine and other acylcarnitines in newborn blood spots by tandem mass spectrometry.

We report the application of tandem mass spectrometry to prospective newborn screening for medium-chain acyl-CoA dehydrogenase (MCAD) deficiency. MCAD deficiency is diagnosed from dried blood spots on filter paper cards from newborns on the basis of the increase of medium chain length acylcarnitines identified by isotope dilution mass spectrometry methods. A robust and accurate semiautomated method for the analysis of medium chain length acylcarnitines as their butyl esters was developed and validated. Quantitative data from the analyses of 113 randomly collected filter paper blood spots from healthy newborns showed low concentrations of medium chain length acylcarnitines such as octanoylcarnitine. The maximum concentration of octanoylcarnitine was 0.22 mumol/L, with the majority being at or below the detection limit. In all 16 blood spots from newborns with confirmed MCAD deficiency, octanoylcarnitine was highly increased [median 8.4 mumol/L (range 3.1-28.3 mumol/L)], allowing easy detection. The concentration of octanoylcarnitine was significantly higher in these 16 newborns (< 3 days of age) than in 16 older patients (ages 8 days to 7 years) with MCAD deficiency (median 1.57 mumol/L, range 0.33-4.4). The combined experience of prospective newborn screening in Pennsylvania and North Carolina has shown a disease frequency for MCAD deficiency of 1 in 17,706. No false-positive and no known false-negative results have been found. A validated method now exists for prospective newborn screening for MCAD deficiency.

Purification of recombinant human precursor acid alpha-glucosidase.

Large quantities of recombinant acid alpha-glucosidase are needed for in vivo experimentation of enzyme replacement therapy in Pompe disease. We describe a new purification method for the purification of this recombinant enzyme from tissue culture medium consisting of concanavalin A affinity chromatography, hydrophobic interaction chromatography, affinity chromatography on Superdex, and anion exchange chromatography. The new method is amenable to scale up, and has increased speed, and improved reproducibility with similar high yield and purification efficiency when compared to previous methods.