Management of Leigh syndrome: Current status and new insights.

Leigh syndrome (LS) is an inherited mitochondrial encephalopathy associated with gene mutations of oxidative phosphorylation pathway that result in early disability and death in affected young children. Currently, LS is incurable and unresponsive to many treatments, although some case reports indicate that supplements can improve the condition. Many novel therapies are being continuously tested in pre-clinical studies. In this review, we summarize the genetic basis of LS, current treatment, pre-clinical studies in animal models and the management of other mitochondrial diseases. Future therapeutical strategies and challenges are also discussed.

Long-term efficacy of miglustat in paediatric patients with Niemann-Pick disease type C.

Niemann-Pick disease type C (NP-C) is a rare inherited neurovisceral disease characterized by progressive neurological manifestations. Oral miglustat was first approved for the treatment of children and adults with NP-C in Europe in 2009. There are still relatively few published data on the long-term efficacy and safety of miglustat in patients with NP-C in clinical practice. We report the effects of up to 6 years of treatment with miglustat 100 mg t.i.d. in five children. Overall, 3/5 patients displayed progressive dysphagia before starting miglustat, and 4/5 showed marked cognitive and/or motor impairment. The mean age at treatment start was 11.6 years, and the median (range) duration of therapy so far is 4 (4.1 to 6.1) years. No treatment dose alterations were required, but therapy was interrupted for 1-3 months at least once in all patients due to supply issues. Swallowing function was stabilised during miglustat therapy, with no significant increase in Han dysphagia scale or aspiration-penetration index scores among four evaluable patients (p > 0.05). Scores on the mini-mental state examination indicated an improvement in cognitive function during the first 3-6 months of miglustat therapy, followed by stabilisation up to 5 years. Ambulatory function remained stable for at least the first 2 years of treatment in most patients, but there was a trend towards deterioration thereafter, possibly related to treatment interruptions. The safety/tolerability profile of miglustat was similar to previous clinical studies, although reports of gastrointestinal disturbances were rare. Overall, miglustat appeared to stabilise key parameters of neurological disease progression.

Expert recommendations for the laboratory diagnosis of MPS VI.

Mucopolysaccharidosis VI (MPS VI) is a lysosomal storage disease caused by a deficiency of N-acetylgalactosamine 4-sulfatase (arylsulfatase B, ASB). This enzyme is required for the degradation of dermatan sulfate. In its absence, dermatan sulfate accumulates in cells and is excreted in large quantities in urine. Specific therapeutic intervention is available; however, accurate and timely diagnosis is crucial for maximal benefit. To better understand the current practices for diagnosis and to establish diagnostic guidelines, an international MPS VI laboratory diagnostics scientific summit was held in February of 2011 in Miami, Florida. The various steps in the diagnosis of MPS VI were discussed including urinary glycosaminoglycan (uGAG) analysis, enzyme activity analysis, and molecular analysis. The following conclusions were reached. Dilute urine samples pose a significant problem for uGAG analysis and MPS VI patients can be missed by quantitative uGAG testing alone as dermatan sulfate may not always be excreted in large quantities. Enzyme activity analysis is universally acknowledged as a key component of diagnosis; however, several caveats must be considered and the appropriate use of reference enzymes is essential. Molecular analysis supports enzyme activity test results and is essential for carrier testing, subsequent genetic counseling, and prenatal testing. Overall the expert panel recommends caution in the use of uGAG screening alone to rule out or confirm the diagnosis of MPS VI and acknowledges enzyme activity analysis as a critical component of diagnosis. Measurement of another sulfatase enzyme to exclude multiple sulfatase deficiency was recommended prior to the initiation of therapy. When feasible, the use of molecular testing as part of the diagnosis is encouraged. A diagnostic algorithm for MPS VI is provided.

Experimental treatment of bilateral fetal chylothorax using in-utero pleurodesis.

OBJECTIVE: To assess the use and efficacy of in-utero pleurodesis for experimental treatment of bilateral fetal chylothorax. METHODS: This was a study of 78 fetuses with bilateral pleural effusion referred to three tertiary referral centers in Taiwan between 2005 and 2009. Fetuses were karyotyped following amniocentesis and the lymphocyte ratio in the pleural effusion was determined following thoracocentesis. Forty-nine (62.8%) fetuses had a normal karyotype and were recognized to have fetal chylothorax; of these, 45 underwent intrapleural injection of 0.1KE OK-432 per side per treatment. We evaluated clinical (hydrops vs. no hydrops) and genetic (mutations in the reported lymphedema-associated loci: VEGFR3, PTPN11, FOXC2, ITGA9) parameters, as well as treatment outcome. Long-term survival was defined as survival to 1 year of age. RESULTS: The overall long-term survival rate (LSR) was 35.6% (16/45); the LSR for non-hydropic fetuses was 66.7% (12/18) and for hydropic fetuses it was 14.8% (4/27). If we included only fetuses with onset of the condition in the second trimester, excluding those with onset in the third trimester, the LSR decreased to 29.4% (10/34). Notably, 29.6% (8/27) of hydropic fetuses had mutations in three of the four loci examined. CONCLUSIONS: OK-432 pleurodesis appeared to be an experimental alternative to the gold-standard technique of thoracoamniotic shunting in non-hydropic fetal chylothorax. In hydropic fetuses, pleurodesis appeared less effective.

Clinical and biochemical features of aromatic L-amino acid decarboxylase deficiency.

OBJECTIVE: To describe the current treatment; clinical, biochemical, and molecular findings; and clinical follow-up of patients with aromatic l-amino acid decarboxylase (AADC) deficiency. METHOD: Clinical and biochemical data of 78 patients with AADC deficiency were tabulated in a database of pediatric neurotransmitter disorders (JAKE). A total of 46 patients have been previously reported; 32 patients are described for the first time. RESULTS: In 96% of AADC-deficient patients, symptoms (hypotonia 95%, oculogyric crises 86%, and developmental retardation 63%) became clinically evident during infancy or childhood. Laboratory diagnosis is based on typical CSF markers (low homovanillic acid, 5-hydroxyindoleacidic acid, and 3-methoxy-4-hydroxyphenolglycole, and elevated 3-O-methyl-l-dopa, l-dopa, and 5-hydroxytryptophan), absent plasma AADC activity, or elevated urinary vanillactic acid. A total of 24 mutations in the DDC gene were detected in 49 patients (8 reported for the first time: p.L38P, p.Y79C, p.A110Q, p.G123R, p.I42fs, c.876G>A, p.R412W, p.I433fs) with IVS6+ 4A>T being the most common one (allele frequency 45%). CONCLUSION: Based on clinical symptoms, CSF neurotransmitters profile is highly indicative for the diagnosis of aromatic l-amino acid decarboxylase deficiency. Treatment options are limited, in many cases not beneficial, and prognosis is uncertain. Only 15 patients with a relatively mild form clearly improved on a combined therapy with pyridoxine (B6)/pyridoxal phosphate, dopamine agonists, and monoamine oxidase B inhibitors.

Stabilization of blood methylmalonic acid level in methylmalonic acidemia after liver transplantation.

Methylmalonic acidemia with complete mutase deficiency (mut(0) type) is an inborn error of metabolism with high mortality and morbidity. LT has been suggested to be a solution to this disease, but elevation of urinary and blood MMA was still observed after LT. In this study, we measured dry blood spot MMA and its precursor propionyl-carnitine (C3-carnitine) for mut(0) patients. The results revealed that when C3-carnitine rose during metabolic stress, MMA rose exponentially (up to 1000 micromol/L) in patients who did not undergo LT. In patients who underwent LT, MMA rose to 100-200 micromol/L when C3-carnitine reached 10-20 micromol/L. However, when C3-carnitine rose further to 40-50 micromol/L, MMA levels just stayed put. Therefore, LT stabilized blood MMA level, though there might be a threshold for blood MMA clearance by the donor liver. This finding should be critical to understand the long-term outcome for LT in methylmalonic acidemia.

Miglustat in patients with Niemann-Pick disease Type C (NP-C): a multicenter observational retrospective cohort study.

Miglustat has been shown to stabilize disease progression in children, juveniles and adults with Niemann-Pick disease type C (NP-C), a rare genetic disorder characterized by progressive neurological deterioration. We report findings from a retrospective observational cohort study assessing the effects of miglustat on neurological disease progression in patients treated in the clinical practice setting. Data from all NP-C patients prescribed miglustat at 25 expert centers were evaluated using a disease disability scale. The scale analyzed four key parameters of neurological disease progression in NP-C (ambulation, manipulation, language, swallowing). Mean individual parameter scores and a composite score were calculated at baseline (time of diagnosis) and up to 4 follow-up visits. Overall, 66 patients were included (mean [SD] age at diagnosis, 9.7 [7.6] years, and at treatment start, 12.8 [9.5] years). The median (range) miglustat exposure was 1.46 (0.05-4.51) years. Mean annual progression was +0.11 score units/year from diagnosis to treatment start, indicating disease progression prior to therapy, and decreasing to -0.01 score units/year from treatment start to last clinic visit, indicating stabilization. Stabilization of neurological disease on miglustat was observed in all age groups, but the magnitude of the effect was greater in patients diagnosed in late childhood and in juveniles and adults. Stabilization of neurological disease was also observed in a subset of 19 patients with extended pre-treatment information. Overall, these data support previous clinical trial findings indicating clinically relevant beneficial effects of miglustat on neurological disease progression in patients with NP-C.

Natural history of Niemann-Pick disease type C in a multicentre observational retrospective cohort study.

Niemann-Pick disease type C (NP-C) is a devastating genetic disorder characterised by progressive neurological deterioration. However, data on the progression of neurological manifestations, particularly across different patient age-of-disease onsets, are limited. This is an observational retrospective cohort study designed to assess the progression of neurological disease in patients with NP-C. Physicians were asked to retrospectively complete a web-based questionnaire for each patient, at diagnosis and at up to three follow-up visits. An NP-C-specific disability scale was used to measure disease progression. The scale comprised four key parameters of neurological disease progression; ambulation, manipulation, language and swallowing. Disease progression was evaluated based on the annual rate of change in each parameter and the composite score using a linear mixed model analysis, and by classifying patients according to the number of worsened parameters during the observation period. Data were collected from 57 patients. The rate of deterioration was similar across the four individual parameters of the disability scale. The mean (95% CI) annual disease progression was +0.12 (0.09, 0.15) units. Among patients with a time interval of at least 1 year between diagnosis and last visit (n=49), 42 (86%) patients had progressed disease and 7 (14%) patients had stable disease. Disease progression was consistently more rapid in patients diagnosed in early childhood, compared with those diagnosed in late childhood, or with juvenile or adult presentation. In conclusion, our findings showed a progression in all four parameters of the disability scale, representing a continuous, unbroken progression of neurological manifestations.

A longitudinal study of Taiwanese sialidosis type 1: an insight into the concept of cherry-red spot myoclonus syndrome.

BACKGROUND AND PURPOSE: Sialidosis type 1 (ST-1) is a neurodegenerative disorder with limited long-term follow-up report. This study is to document the chronological profile of ST-1. METHODS: We perform serial analysis of 17 Taiwanese patients with ST-1 focusing on evolution of clinical features, electrophysiological findings, genetic studies, and neuroimage examinations. RESULTS: All patients had a mutation at 554A-->G in exon 3 of the NEU1 gene causing Ser182Gly substitution. Fifteen patients were homozygous. Two patients were heterozygous with novel mutations, 956C-->T causing Ala319Val in one and 163C-->T causing Gln55stop codon in the other. The neuraminidase activity was markedly decreased in all 11 available patients. Only three patients (17.6%) manifested the macular cherry-red spot. The majority of patients (82.3%) developed full-blown manifestation of myoclonus, ataxia, and seizures within 5 years. Abnormal somatosensory evoked potentials with giant cortical waves were found in all patients. Prolonged P100 peak latency of the visual evoked potentials (VEPs) were found in 16 patients (94.1%) in the early stage even without visual symptoms. CONCLUSION: ST-1 in Taiwanese population illustrates distinct characteristics of phenotype with infrequent cherry-red spot. We suggest to screen the NEU1 mutations in patients presenting action myoclonus with abnormal VEPs, even without macular cherry-red spots.

Simultaneous detection of mitochondrial DNA depletion and single-exon deletion in the deoxyguanosine gene using array-based comparative genomic hybridisation.

Intragenic exonic deletions, which cannot be detected by direct DNA sequencing, are a common cause of Mendelian disease. Array-based comparative genomic hybridisation (aCGH) is now widely used for the clinical diagnosis of large chromosomal deletions, but not small deletions or analysis of the mitochondrial genome. An oligonucleotide-based microarray that provides high-density coverage of the entire mitochondrial genome and nuclear genes related to mitochondrial disorders has been developed. In this report, the case of an infant referred with tyrosinaemia on newborn screening who developed liver failure is presented. DNA sequencing revealed a heterozygous missense mutation (c.679G>A, p.E227K) in the deoxyguanosine gene (DGUOK). Oligonucleotide aCGH allowed simultaneous detection of an intragenic heterozygous deletion of exon 4 of DGUOK and mitochondrial DNA depletion in blood and liver. Screening of the parents' DNA samples indicated that the patient was compound heterozygous for these mutations. An older sibling who had died from liver failure was then retrospectively diagnosed with the same mutations. This report shows the clinical utility of this oligoarray in the detection of changes in DNA copy number in both the mitochondrial and nuclear genomes, thus greatly improving the molecular diagnosis of mitochondrial disorders caused by nuclear genes involved in mitochondrial DNA biosynthesis.

Identification of eight novel mutations of the acid alpha-glucosidase gene causing the infantile or juvenile form of glycogen storage disease type II.

Glycogen-storage disease type II (GSDII; OMIM #232300), an autosomal recessive disorder caused by a deficiency of the glycogen hydrolysis enzyme acid alpha-glucosidase (acid GAA; acid maltase, EC. 3.2.10.20), results in the accumulation of glycogen in the lysosome. We performed a molecular genetic study on 29 patients with infantile-onset glycogen-storage disease type II (GSDII), 6 with juvenile-onset GSDII and one carrier for GSDII. Seventeen different mutations were identified among them; 8 were novel mutations: c.421C > A (p.L141M), c.872T > C (p.L291P), c.893A > C (p.Y298S), c.1375G > A (p.D459N), c.1437G > C (p.K479N), c.1509_1511del (p.A504del), c.1960T > C (p.S654P), and c.2174G > C (p.R725P). One of the mutations identified, c.2238G > C (p.W746C), which was a sequence change of unknown pathogenic significance causing diminished enzyme activity,was found homozygously in a juvenile-onset patient. We also found a juvenile-onset patient with homozygote c.1935C > A mutation which was frequently found in infantile-onset patients. In addition to mutations, we also identified 14 new polymorphisms in the acid alpha-glucosidase gene. The genotype/phenotype correlations indicated that c.2238G > C (p.W746C) is correlated with juvenile- onset GSDII and that c.872T > C (p.L291P) and c.1411_1414del (p.E471fsX5) are correlated with infantile-onset GSDII. Mutational analysis of GAA is useful in genetic counseling and prenatal diagnosis of the disease.

Detection and imaging of non-contractile inclusions and sarcomeric anomalies in skeletal muscle by second harmonic generation combined with two-photon excited fluorescence.

The large size of the multinucleated muscle fibers of skeletal muscle makes their examination for structural and pathological defects a challenge. Sections and single fibers are accessible to antibodies and other markers but imaging of such samples does not provide a three-dimensional view of the muscle. Regrettably, bundles of fibers cannot be stained or imaged easily. Two-photon microscopy techniques overcome these obstacles. Second harmonic generation (SHG) by myosin filaments and two-photon excited fluorescence (2PEF) of mitochondrial and lysosomal components provides detailed structural information on unstained tissue. Furthermore, the infrared exciting light can penetrate several layers of muscle fibers and the minimal processing is particularly valuable for fragile biopsies. Here we demonstrate the usefulness of SHG, combined with 2PEF, to reveal enlarged lysosomes and accumulations of non-contractile material in muscles from the mouse model for the lysosomal storage disorder Pompe disease (PD), and in biopsies from adult and infant PD patients. SHG and 2PEF also detect sarcomeric defects that may presage the loss of myofibrils in atrophying muscle and signify loss of elasticity. The combination of SHG and 2PEF should be useful in the analysis and diagnosis of a wide range of skeletal muscle pathologies.

Deficiency of the carnitine transporter (OCTN2) with partial N-acetylglutamate synthase (NAGS) deficiency.

A patient with recurrent episodes of hyperammonaemia (highest ammonia level recorded 229 micromol/L, normal 9-33) leading to altered levels of consciousness was diagnosed with partial N-acetylglutamate synthase (NAGS) deficiency (9% residual activity) at age 5 years and was treated with ammonia-conjugating agents (Ucephan 250 mg/kg per day and later sodium phenylbutyrate 200-250 mg/kg per day) for 15 years. A chronically low serum carnitine level (pretreatment plasma free carnitine 4 nmol/L, normal 37 +/- 8 nmol/L; total carnitine 8 nmol/L, normal 46 +/- 10) was assumed to be secondary and was treated with supplemental carnitine (30-50 mg/kg per day). Hypoglycaemia (blood sugar 35 mg/dl, normal 70-100), cardiomegaly, and fatty liver were also noted at diagnosis. The patient died unexpectedly at age 20 years. In retrospect, it was learned that the patient had stopped his carnitine without medical consultation several weeks prior to his death. Additional molecular investigations identified two mutations (R254X and IVS3 + 1G > A) in the patient's OCTN2 (SLC22A5) gene, consistent with a diagnosis of primary carnitine deficiency due to carnitine transporter defect. R245X is a founder mutation in Southern Chinese populations. It is unknown whether the original NAGS deficiency was primary or secondary, but molecular analysis of the NAGS gene failed to identify mutations. Urea cycle enzyme expression may be affected by fatty acid suppression of an AP-1 binding site in the promoter enhancer region of the urea cycle gene. Regardless, it is clear that the NAGS abnormality has led to delay of recognition of the OCTN2 defect, and modified the clinical course in this patient.

Treatment of Niemann-Pick disease type C in two children with miglustat: initial responses and maintenance of effects over 1 year.

Niemann-Pick disease type C (NP-C) is a lipid storage disorder characterized by the accumulation of unesterified cholesterol and glycolipids in the lysosomal/late endosomal system of certain cells in the central nervous system (CNS) and visceral organs. Clinical symptoms include progressive neurological deterioration and visceral organomegaly. Miglustat, a small iminosugar molecule approved for the treatment of Gaucher disease, reversibly inhibits glucosylceramide synthase, which catalyses the first committed step in glycosphingolipid synthesis. The physicochemical properties of miglustat allow it to cross the blood-brain barrier and suggest possible benefits in lysosomal storage diseases affecting the CNS. Here, we present findings in two children with NP-C, aged 14 years (patient 1) and 9 years (patient 2), treated with miglustat for 1 year. Before treatment, patient 1 presented with severe difficulties in swallowing and walking, and patient 2 with problems mostly affecting communication and social interaction. Videofluoroscopic studies in patient 1 demonstrated a substantial improvement in swallowing by month 6 of treatment, and ambulation index measurements indicated improved walking. Mini Mental-State Examination (MMSE) assessments in patient 2 showed cognitive improvement by month 6, which was sustained up to month 12. Liver/spleen volume and plasma chitotriosidase activities were stabilized in both cases. There was no weight loss during treatment. Patient 1 experienced severe but self-limiting paresthesia, which was not associated with peripheral neuropathy. We conclude that miglustat can provide therapeutic benefits in CNS symptoms and allows stabilization of systemic disease in childhood-onset NP-C. Further follow-up is crucial to determine the long-term maintenance of these effects.

Prenatal diagnosis and genetic counseling of mucopolysaccharidosis type II (Hunter syndrome).

We present prenatal diagnosis of mucopolysaccharidosis type II (MPS II) (Hunter syndrome) and demonstrate marked mucopolysaccharide deposition in multiple vital organs in a 22-gestational-week affected fetus. Level II ultrasound showed cardiomegaly and hepatomegaly. Histological examinations of the fetal vital organs manifested marked mucopolysaccharide deposition. We suggest that any therapeutic approach and counseling for prenatally diagnosed MPS II should consider the early signs of in utero marked mucopolysaccharide storage.