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Fulltext Selective screening for detection of mucopolysaccharidoses in Malaysia; A two-year study (2014-2016)

Omar A, Jalil JA, Shakrin NM, Ngu LH, Yunus ZM

Mol Genet Metab Rep, 2019 Jun;19:100469.
PMID: 31193155 DOI: 10.1016/j.ymgmr.2019.100469

Introduction: Mucopolysaccharidoses (MPS) are a group of inherited disorders caused by the deficiency of a specific lysosomal enzyme involved in glycosaminoglycans (GAGs) degradation. This enzyme deficiency leads to accumulation of GAGs in the lysosomes, resulting in organ dysfunction and enlargement. We aimed to detect cases of MPS in patients with suggestive signs and symptoms.
Methods: This was a 2-year cross-sectional study conducted during June 2014 to May 2016. Urine and whole blood samples were taken from high-risk MPS patients. All urine samples were analysed for GAGs and characterised by high resolution electrophoresis (HRE). Whole blood was collected in ethylenediaminetetraacetic acid (EDTA) tube and analysed for specific enzymes based on the clinical history and HRE findings.
Results: From the 60 samples tested, 15 were positive for MPS; (Type I = 1), (Type II = 4), (Type IIIA = 3), (Type IVA = 1), (Type VI = 6). The overall prevalence of MPS among high-risk Malaysian patients was 26% (95% CI 14.72% to 37.86%). One patient had mucolipidosis. The mean age of patients when diagnosed was 5 years old. Patients with MPS were more likely to present with hepatosplenomegaly compared to other symptoms (OR = 0.974, p 
RANBP2 susceptibility to infection-induced encephalopathy: Clinicoradiologic and molecular description in a Malaysian family

Chew HB, Ngu LH

Mol Genet Metab Rep, 2020 Sep;24:100627.
PMID: 32760653 DOI: 10.1016/j.ymgmr.2020.100627

Pathogenic variants in RANBP2 cause autosomal dominant familial and recurrent Acute Necrotizing Encephalopathy of Childhood (ANEC). Affected children typically experience a 3-stage disease: a 3 to 5 days prodrome of non-specific febrile illness, acute encephalopathy, and recovery with or without neurological sequelae or death. Neuroradiological finding of bilateral symmetrical thalamic lesions raise the suspicion of this diagnosis. A devastating disease, reported mortality approaches 1/3 of those affected and only approximately 10% of patients recover completely without sequelae. We report a Malaysian family with RANBP2 pathogenic variant c.1754C>T (p.Thr585Met). The clinical presentation and course over a maximum of 7 years, as well as neuroradiological features of the 3 affected children are described. In contrast to the reported high mortality and morbidity, our patients have recovered with minor sequelae. We would like to highlight the absence of pathogenic variants in both parents' blood, raising the possibility of germline mosaicism in one of the parents as the underlying genetic mechanism of inheritance. To our knowledge, this is the first report of germline mosaicism in RANBP2 Susceptibility to Infection-induced Encephalopathy.
Fulltext Fourteen new mutations of BCKDHA, BCKDHB and DBT genes associated with maple syrup urine disease (MSUD) in Malaysian population

Ali EZ, Ngu LH

Mol Genet Metab Rep, 2018 Dec;17:22-30.
PMID: 30228974 DOI: 10.1016/j.ymgmr.2018.08.006

Maple syrup urine disease (MSUD) is a rare autosomal recessive metabolic disorder. This disorder is usually caused by mutations in any one of the genes; BCKDHA, BCKDHB and DBT, which represent E1α, E1β and E2 subunits of the branched-chain α-keto acid dehydrogenase (BCKDH) complex, respectively. This study presents the molecular characterization of 31 MSUD patients. Twenty one mutations including 14 new mutations were identified. The BCKDHB gene was the most commonly affected (45.2%) compared to BCKDHA gene (16.1%) and DBT gene (38.7%). In silico webservers predicted all mutations were disease-causing. In addition, structural evaluation disclosed that all new missenses in BCKDHA, BCKDHB and DBT genes affected stability and formation of E1 and E2 subunits. Majority of the patients had neonatal onset MSUD (26 of 31). Meanwhile, the new mutation; c.1196C > G (p.S399C) in DBT gene was noted to be recurrent and found in 9 patients. Conclusion: Our findings have expanded the mutational spectrum of the MSUD and revealed the genetic heterogeneity among Malaysian MSUD patients. We also discovered the p.S399C from DBT gene was noted as a recurrent mutation in Malay community and it suggested the existence of common and unique mutation in Malay population.
Fulltext Identification of mutations in Malaysian patients with argininosuccinate lyase (ASL) deficiency

Ali EZ, Yakob Y, Ngu LH

Mol Genet Metab Rep, 2019 Dec;21:100525.
PMID: 31709144 DOI: 10.1016/j.ymgmr.2019.100525

Argininosuccinate lyase (ASL) deficiency impairs the function of the urea cycle that detoxifies blood ammonia in the body. Mutation that occurs in the ASL gene is the cause of occurrence of ASL deficiency (ASLD). This deficiency causes hyperammonemia, hepatopathy and neurodevelopmental delay in patients. In this study, the clinical characteristics and molecular analysis of 10 ASLD patients were presented. 8 patients were associated with severe neonatal onset, while the other 2 were associated with late onset. Molecular analysis of ASL gene identified four new missense variants, which were c.778C>T, p.(Leu260Arg), c.1340G>C, p.(Ser447Thr), c.436C>G, p.(Arg146Gly) and c.595C>G, p.(Leu199Val) and four reported missense variants, which were c.638G>A, p.(Arg213Gln); c.556C>T, p.(Arg186Trp), c.578G>A, p.(Arg193Gln) and c.436C>G, p.(Arg146Trp). In silico servers predicted all new and reported variants as disease-causing. Structural examination exhibited that all pathogenic variants affected the stability of the tetrameric ASL structure by disturbing the bonding pattern with the neighboring residues.
Conclusion: This study revealed the genetic heterogeneity among Malaysian ASL patients. This study has also expanded the mutational spectrum of the ASL.
Fulltext Clinical, biochemical and mutational findings in biotinidase deficiency among Malaysian population

Mardhiah M, Azize NAA, Yakob Y, Affandi O, Hock NL, Rowani MR, et al.

Mol Genet Metab Rep, 2020 Mar;22:100548.
PMID: 32300527 DOI: 10.1016/j.ymgmr.2019.100548

Introduction: Biotinidase deficiency (BD) is an autosomal recessively inherited disorder characterized by developmental delay, seizures, hypotonia, ataxia, skin rash/eczema, alopecia, conjunctivitis/visual problem/optic atrophy and metabolic acidosis. Delayed diagnosis may lead to irreversible neurological damage.
Methodology: Clinically suspected patients were screened for biotinidase level by a fluorometry method. Profound BD patients were confirmed by mutation analysis of BTD gene.
Results: 9 patients had biotinidase activity of less than 77 U. 3 patients (33%) had profound BD while 6 patients (67%) had partial BD. Compound heterozygous mutations were detected at c.98_104delinsTCC p.(Cys33Phefs*36) in Exon 2 and c.833T>C p.(Leu278Pro) in Exon 4 in two patients and a homozygous mutation at c.98_104delinsTCC p.(Cys33Phefs*36) in Exon 2 in another patient.
Conclusion: Correct diagnosis lead to early treatment and accurate management of patient. Biochemical screening of BD in symptomatic child is prerequisite to determine enzyme status however molecular confirmation is vital in differentiating individuals with profound biotinidase deficiency from partial biotinidase deficiency and also individuals' carriers.
Fulltext Case report of treatment experience with idursulfase beta (Hunterase) in an adolescent patient with MPS II

Ngu LH, Ong Peitee W, Leong HY, Chew HB

Mol Genet Metab Rep, 2017 Sep;12:28-32.
PMID: 28540187 DOI: 10.1016/j.ymgmr.2017.05.002

Mucopolysaccharidosis (MPS) II or Hunter syndrome is a chronic, progressive, multi-systemic illness associated with significant morbidity and early mortality. Available evidence in Asian populations shows that Hunter syndrome has a mean age of onset of 2 to 5 years and a life expectancy of 13 years in more severely affected individuals, with respiratory failure reported as the leading cause of death. Enzyme replacement therapy (ERT) with idursulfase (Elaprase, Shire Pharmaceuticals) and idursulfase beta (Hunterase, Green Cross Corp) are the only approved treatment for patients with MPS II. While these agents have the same amino acids, they have different glycosylation patterns because they are produced in different cell lines via different manufacturing processes. In previous studies, the beneficial effects of idursulfase beta have been confirmed in patients up to 35 years of age, without serious treatment-related safety concerns. The major drawbacks associated with ERT include the potential development of serious infusion-related anaphylactic reactions and up to 50% of treated patients develop anti-IDS antibodies. Here we report the case of a 13-year-old Malaysian patient with attenuated MPS II who developed troublesome infusion-associated reactions while receiving idursulfase treatment but tolerated and responded favorably to idursulfase beta.
Fulltext Long-term experience with idursulfase beta (Hunterase) in two adolescent patients with MPS II: A case series

Chan MY, Nelson AJ, Ngu LH

Mol Genet Metab Rep, 2023 Sep;36:100991.
PMID: 37670899 DOI: 10.1016/j.ymgmr.2023.100991

Mucopolysaccharidosis (MPS) type II (Hunter syndrome) is a rare X-linked, recessive, lysosomal storage disorder caused by the deficit of the enzyme iduronate 2-sulfatase (IDS), resulting in accumulation of glycosaminoglycans (GAGs) impairing cellular function in multiple organ systems. Idursulfase (Elaprase, Takeda Pharmaceuticals) and idursulfase beta (Hunterase, GC Biopharma Corp.) are the two currently available enzyme replacement therapies (ERT) for MPS II in Malaysia. ERT in patients with MPS II is associated with improvements in somatic symptoms, pulmonary function, endurance, joint mobility, and quality of life. Though mostly well tolerated, infusion-associated reactions (IARs), such as allergic (IgE-mediated) or nonallergic (non- immunologic) reactions can develop during ERT. In certain cases, when patients develop recurrent IARs despite reduced infusion rate and premedication, either interruption or cessation of ERT might be necessary. However, interruption of ERT is associated with worsening of clinical symptoms such as recurrent respiratory infections, difficulty in standing and walking, and increased joint stiffness, emphasizing the need for continuation of ERT. Here we report successful long-term experience with the use of idursulfase beta in two adolescent Malaysian patients with MPS II, who experienced recurrent infusion-associated reactions warranting discontinuation of ERT with idursulfase.