Wee Teik Keng

Hospital Kuala Lumpur, Kuala Lumpor, Kuala Lumpur, Malaysia

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Publications (13)17.87 Total impact

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    Dataset: PND
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    ABSTRACT: Tuberous sclerosis complex is an autosomal dominant neurocutaneous disorder affecting multiple organs. Tuberous sclerosis complex is caused by mutation in either one of the two disease-causing genes, TSC1 or TSC2, encoding for hamartin and tuberin, respectively. TSC2/PKD1 contiguous gene deletion syndrome is a very rare condition due to deletion involving both TSC2 and PKD1 genes. Tuberous sclerosis complex cannot be easily diagnosed since there is no pathognomonic feature, although there are consensus diagnostic criteria for that. Mutation analysis is useful and plays important roles. We report here two novel gross deletions of TSC2 gene in Malay patients with tuberous sclerosis complex and TSC2/PKD1 contiguous gene deletion syndrome, respectively.
    Japanese Journal of Clinical Oncology 03/2014; 44(5). DOI:10.1093/jjco/hyu024 · 1.75 Impact Factor
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    ABSTRACT: Background: Lesch–Nyhan disease (LND) is a rare X-linked recessive neurogenetic disorder caused by deficiency of the purine salvage enzyme hypoxanthine phosphoribosyltransferase (HPRT, EC 2.4.2.8) which is responsible for recycling purine bases into purine nucleotides. Affected individuals have hyperuricemia leading to gout and urolithiasis, accompanied by a characteristic severe neurobehavioural phenotype with compulsive self-mutilation, extrapyramidal motor disturbances and cognitive impairment. Aim: For its theoretical therapeutic potential to replenish the brain purine nucleotide pool, oral supplementation with S-adenosylmethi-onine (SAMe) was trialed in 5 Malaysian children with LND, comprising 4 related Malay children from 2 families, including an LND girl, and a Chinese Malaysian boy. Results: Dramatic reductions of self-injury and aggressive behaviour, as well as a milder reduction of dystonia, were observed in all 5 patients. Other LND neurological symptoms did not improve during SAMe therapy. Discussion: Molecular mechanisms proposed for LND neuropathology include GTP depletion in the brain leading to impaired dopamine synthesis, dysfunction of G-protein-mediated signal transduction, and defective developmental programming of dopa-mine neurons. The improvement of our LND patients on SAMe, particularly the hallmark self-injurious behaviour, echoed clinical progress reported with another purine nucleotide depletion disorder, Arts Syndrome, but contrasted lack of benefit with the purine disorder adenylosuccinate lyase deficiency. This first report of a trial of SAMe therapy in LND children showed remarkably encour-aging results that warrant larger studies. Crown copyright Ó 2013 Published by Elsevier B.V. on behalf of The Japanese Society of Child Neurology. All rights reserved.
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    ABSTRACT: Background: Lesch-Nyhan disease (LND) is a rare X-linked recessive neurogenetic disorder caused by deficiency of the purine salvage enzyme hypoxanthine phosphoribosyltransferase (HPRT, EC 2.4.2.8) which is responsible for recycling purine bases into purine nucleotides. Affected individuals have hyperuricemia leading to gout and urolithiasis, accompanied by a characteristic severe neurobehavioural phenotype with compulsive self-mutilation, extrapyramidal motor disturbances and cognitive impairment. Aim: For its theoretical therapeutic potential to replenish the brain purine nucleotide pool, oral supplementation with S-adenosylmethionine (SAMe) was trialed in 5 Malaysian children with LND, comprising 4 related Malay children from 2 families, including an LND girl, and a Chinese Malaysian boy. Results: Dramatic reductions of self-injury and aggressive behaviour, as well as a milder reduction of dystonia, were observed in all 5 patients. Other LND neurological symptoms did not improve during SAMe therapy. Discussion: Molecular mechanisms proposed for LND neuropathology include GTP depletion in the brain leading to impaired dopamine synthesis, dysfunction of G-protein-mediated signal transduction, and defective developmental programming of dopamine neurons. The improvement of our LND patients on SAMe, particularly the hallmark self-injurious behaviour, echoed clinical progress reported with another purine nucleotide depletion disorder, Arts Syndrome, but contrasted lack of benefit with the purine disorder adenylosuccinate lyase deficiency. This first report of a trial of SAMe therapy in LND children showed remarkably encouraging results that warrant larger studies.
    Brain & development 09/2013; 36(7). DOI:10.1016/j.braindev.2013.08.013 · 1.54 Impact Factor
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    ABSTRACT: X-linked adrenoleukodystrophy is caused by a defective peroxisomal membrane transporter, ABCD1, responsible for transporting very-long-chain fatty acid substrate into peroxisomes for degradation. The main biochemical defect, which is also one of the major diagnostic hallmarks, of X-linked adrenoleukodystrophy is the accumulation of saturated very-long-chain fatty acids in all tissues and body fluids. Direct and reverse-transcribed polymerase chain reactions followed by DNA sequencing-based mutational analyses were performed on one Taiwanese and three Malaysian X-linked adrenoleukodystrophy families. A novel splicing donor site mutation (c.1272+1g>a) was identified in a Taiwanese X-linked adrenoleukodystrophy patient, resulting in a deletion of 121 bp and a premature stop codon (p.Val425fs*92) in messenger-RNA transcript. This deletion is caused by the activation of a cryptic splicing donor site in exon 4 of the ABCD1 gene, which is consistent with the prediction by several online algorithms. In addition, three previously described missense mutations (c.965T>C, c.1978C>T, and c.2006A>G), leading to aberrant ABCD1 of p.Leu322Pro, p.Arg660Trp, and p.His669Arg, were also identified in Malaysian probands. This is the first report to unveil unequivocally that cryptic splicing-induced aberrant messenger-RNA carrying an internal frameshift deletion results from an intronic mutation in the ABCD1 gene. Furthermore, a polymorphism in intron 9 (c.1992-32c/t; refSNP: rs4898368) of the ABCD1 gene was commonly observed in both Taiwanese and Malaysian populations.
    Pediatric Neurology 07/2013; 49(3). DOI:10.1016/j.pediatrneurol.2013.04.021 · 1.50 Impact Factor
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    ABSTRACT: OBJECTIVE: The pediatric neurotransmitter disorders (PND) represent a group of neurological disorders characterized by abnormalities of neurotransmitter synthesis and breakdown. The disorders of dopamine and serotonin synthesis are aromatic amino acid decarboxylase (AADC) deficiency, tyrosine hydroxylase (TH) deficiency, and disorders of tetrahydrobiopterin (BH4) synthesis. We studied 22 patients with PND. METHODS: We retrospectively reviewed their clinical data. RESULTS: Nineteen patients have combined deficiency of dopamine, catecholamines and serotonin as a result of AADC deficiency (10 patients) and BH4 deficiency (7 patients). Five patients were lack in dopamine and catecholamines as a consequence of TH deficiency. Their diagnoses were established by measurement of CSF monoamine metabolites and pterins; and mutations study. Symptoms were obvious from early infancy in all except one patient with BH4 deficiency who was diagnosed presymptomatically. Motor dysfunction was the most prominent clinical feature: truncal hypotonia, hypokinesia, dystonia and oculogyric crises. Extraneurological symptoms were common: hypersalivation, hyperhidrosis, nasal congestion and sleep disturbances. One patient had recurrent hypoglycaemia. All patients with BH4 deficiency had good and sustained clinical improvements to the combined therapy of BH4, L-dopa and 5-hydroxytryptophan. Only one patient with TH deficiency had significant clinical improvement with L-dopa therapy. All patients with AADC deficiency were treated with combination of vitamin B6, dopamine agonists and MAO inhibitors and almost all had suboptimal therapeutic effects whereas adverse effects were frequently observed. CONCLUSION: Response to treatment and long-term outcomes are highly variable among patients with PND due to different genetic defects. Good clinical outcome was achievable in patients with BH4 deficiency.
    35th Malaysian Paediatrics Association Congress; 06/2013
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    H B Chew · L H Ngu · W T Keng
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    ABSTRACT: A rare syndrome of rapid-onset obesity with hypothalamic dysfunction, hypoventilation and autonomic dysregulation (ROHHAD) has been recently described. We report the first patient with this syndrome in Southeast Asia and review reported cases to date. Our patient was good health with normal development until the age of 2. He then developed hyperphagic obesity, hypersomnolence, seizures, alveolar hypoventilation, central hypothyroidism, sodium and water dysregulation, gastrointestinal dysmotility, strabismus, disordered temperature and irregular heart rate, altered sweating, delayed puberty, mental retardation and recurrent respiratory tract infections. The cardiomyopathy with heart failure and abnormal cerebral spinal fluid (CSF) neurotransmitter analysis present in our patient have not been reported previously. Tumours of the sympathetic nervous system are known to be associated with this syndrome but had not been found in our patient at the time of reporting. We highlight the difficulty of achieving the diagnosis of ROHHAD syndrome and its overlap with other well-established disease entities. The mortality and morbidity resulting from the high incidence of cardiorespiratory arrest may be prevented by early ventilatory support.
    Case Reports 01/2011; 2011. DOI:10.1136/bcr.02.2010.2706
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    ABSTRACT: We analysed a DNA sample from a father and child who were both heterozygous for a 7 base pair inser-tion in the MEST gene differentially-methylated promoter region, previously shown by PCR analysis of bisulphite-treated DNA to be on the methylated allele in the unaffected father and the unmethylated allele in the affected child. PCR from genomic DNA was then carried out using a commercial PCR kit with its recommended initial DNA denaturation step of 2 minutes. Subsequent sequence analysis showed that only the non-methylated allele had been ampli-fied, the father appearing to be homozygous normal and the child appearing to have a homozygous 7 b.p. insertion. The PCR protocol was then modified in order to use a longer DNA denaturation stage prior to the addition of the polymerase enzyme. Upon do-ing so, both the methylated and non-methylated al-leles were then identifiable by sequencing with the mutation appearing in its expected heterozygous form. These results highlight the fact that the methy-lation status of DNA can affect the denaturation rate prior to PCR and result in allele drop-out, showing that the standard protocols of commercial kits should be used with caution when working with methylated regions of DNA.
    Open Journal of Genetics 01/2011; 01(02). DOI:10.4236/ojgen.2011.12003
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    ABSTRACT: Citrin deficiency, aetiologically linked to mutations of SLC25A13 gene, has two clinical phenotypes, namely adult-onset type II citrullinaemia (CTLN2) and neonatal/infantile intrahepatic cholestasis, caused by citrin deficiency (NICCD). Malaysian patients with NICCD, especially of Malay and East Malaysian indigenous descent, have never been reported in the literature. We present the clinical features, biochemical findings and results of molecular analysis in 11 Malaysian children with NICCD. In this case series, all patients manifested prolonged cholestatic jaundice and elevated citrulline levels. The other more variable features included failure to thrive, bleeding diathesis, hypoproteinaemia, abnormal liver enzymes, prolonged coagulation profile, hyperammonaemia, hypergalactosaemia, multiple aminoacidaemia, elevated α-feto protein and urinary orotic acid as well as liver biopsies showing hepatitis and steatosis. DNA analysis of SLC25A13 revealed combinations of 851del4(Ex9), IVS16ins3kb and 1638ins23. Most of our patients recovered completely by the age of 22 months. However, one patient had ongoing symptoms at the time of reporting and one had died of liver failure. Since a small percentage of children with NICCD will develop CTLN2 and the mechanisms leading to this is yet to be defined, ongoing health surveillance into adulthood is essential.
    Journal of Inherited Metabolic Disease 12/2010; DOI:10.1007/s10545-010-9248-6 · 4.14 Impact Factor
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    ABSTRACT: To describe the current treatment; clinical, biochemical, and molecular findings; and clinical follow-up of patients with aromatic l-amino acid decarboxylase (AADC) deficiency. 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. 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%). 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.
    Neurology 07/2010; 75(1):64-71. DOI:10.1212/WNL.0b013e3181e620ae · 8.30 Impact Factor
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    ABSTRACT: Mowat-Wilson syndrome (MWS) is a recently delineated mental retardation; a multiple congenital anomaly syndrome characterised by a typical facial gestalt, Hirschsprung disease or severe constipation, genitourinary anomaly, congenital heart defects, agenesis of corpus callosum and eye defects. Some cases also present with epilepsy, growth retardation with microcephaly and speech impairment. MWS was first described in 1998 by Mowat et al, and approximately 180 cases have been reported as of August 2008. The syndrome occurs as a result of heterozygous mutations or deletions in the zinc finger E-box-binding homeobox 2 gene, ZEB2, previously called ZFHX1B (SIP1). Most cases reported so far were sporadic occurrences; however, rare cases of sibling recurrence have been cited. The facial phenotype is particularly important for the initial clinical diagnosis and provides the hallmark, warranting ZEB2 mutational analysis even in the absence of Hirschsprung disease. We present the first two molecularly confirmed Malaysian MWS patients, one of whom has a novel mutation.
    Singapore medical journal 03/2010; 51(3):e54-7. · 0.63 Impact Factor

Publication Stats

61 Citations
17.87 Total Impact Points

Institutions

  • 2011–2014
    • Hospital Kuala Lumpur
      Kuala Lumpor, Kuala Lumpur, Malaysia
    • University of Malaya
      • Department of Paediatrics
      Kuala Lumpur, Kuala Lumpur, Malaysia