Clinical course, mutations and its functional characteristics of infantile-onset Pompe disease in Thailand.

BACKGROUND: Pompe disease is a lysosomal storage disorder caused by the deficiency of acid alpha-glucosidase (EC. 3.2.1.20) due to mutations in human GAA gene. The objective of the present study was to examine clinical and molecular characteristics of infantile-onset Pompe disease (IOPD) in Thailand. METHODS: Twelve patients with infantile-onset Pompe disease (IOPD) including 10 Thai and two other Asian ethnicities were enrolled. To examine the molecular characteristics of Pompe patients, GAA gene was analyzed by PCR amplification and direct Sanger-sequencing of 20 exons coding region. The novel mutations were transiently transfected in COS-7 cells for functional verification. The severity of the mutation was rated by study of the GAA enzyme activity detected in transfected cells and culture media, as well as the quantity and quality of the proper sized GAA protein demonstrated by western blot analysis. The GAA three dimensional structures were visualized by PyMol software tool. RESULTS: All patients had hypertrophic cardiomyopathy, generalized muscle weakness, and undetectable or < 1% of GAA normal activity. Three patients received enzyme replacement therapy with variable outcome depending on the age of the start of enzyme replacement therapy (ERT). Seventeen pathogenic mutations including four novel variants: c.876C > G (p.Tyr292X), c.1226insG (p.Asp409GlyfsX95), c.1538G > A (p.Asp513Gly), c.1895 T > G (p.Leu632Arg), and a previously reported rare allele of unknown significance: c.781G > A (p.Ala261Thr) were identified. The rating system ranked p.Tyr292X, p. Asp513Gly and p. Leu632Arg as class "B" and p. Ala261Thr as class "D" or "E". These novel mutations were located in the N-terminal beta-sheet domain and the catalytic domain. CONCLUSIONS: The present study provides useful information on the mutations of GAA gene in the underrepresented population of Asia which are more diverse than previously described and showing the hotspots in exons 14 and 5, accounting for 62% of mutant alleles. Almost all mutations identified are in class A/B. These data can benefit rapid molecular diagnosis of IOPD and severity rating of the mutations can serve as a partial substitute for cross reactive immunological material (CRIM) study.

p.X654R IDUA variant among Thai individuals with intermediate mucopolysaccharidosis type I and its residual activity as demonstrated in COS-7 cells.

BACKGROUND: Mucopolysaccharidosis type I (MPS I) is a rare autosomal-recessive disorder caused by defects in alpha-L-iduronidase (IDUA), a lysosomal enzyme encoded by the IDUA gene. Herein, we characterized IDUA mutations underlying mucopolysaccharidosis type I intermediate form (Hurler-Scheie syndrome) and its molecular pathogenic mechanisms. METHODS: Clinical data, activity of the IDUA enzyme in leukocytes, and a mutation of the IDUA gene were analyzed. Pathogenesis associated with an IDUA mutation was further investigated by evaluating the mutant cDNA sequence, protein expression and activity in COS-7 cells. RESULTS: Five unrelated patients were identified to have clinical diagnosis of intermediate form of MPS I (Hurler-Scheie) and exhibited low-to-absent levels of leukocyte IDUA activity. Genetic analysis revealed homozygous c.*1T>C (p.X654R) mutation in two patients and compound heterozygosity between the c.*1T>C and another allele including c.265G>A (p.R89Q), c.935G>A (p.W312X), or c.1138 C>T (p.Q380X), each in a single patient. Sequencing the 3'RACE product of the c.*1T>C (p.X654R) allele indicated a 38-amino acids elongation of the mutant protein. COS-7 cells expressing IDUA with the mutations exhibited extremely low levels or complete absence of enzyme activity compared to wild-type IDUA. Western blot analysis detected no protein in p.W312X and p.Q380X samples, while an elevated molecular mass and a different pattern of protein bands were found in p.X654R specimen compared with the wild type IDUA. CONCLUSIONS: Mutational spectrum underlying intermediate MPS I is expanded. Our data suggest that the p.X654R is an intermediate IDUA mutant allele with residual enzyme activity. It can lead to intermediate or milder form of MPS I depending on another associated allele.

An Economic Evaluation of Neonatal Screening for Inborn Errors of Metabolism Using Tandem Mass Spectrometry in Thailand.

BACKGROUND: Inborn errors of metabolism (IEM) are a rare group of genetic diseases which can lead to several serious long-term complications in newborns. In order to address these issues as early as possible, a process called tandem mass spectrometry (MS/MS) can be used as it allows for rapid and simultaneous detection of the diseases. This analysis was performed to determine whether newborn screening by MS/MS is cost-effective in Thailand. METHOD: A cost-utility analysis comprising a decision-tree and Markov model was used to estimate the cost in Thai baht (THB) and health outcomes in life-years (LYs) and quality-adjusted life year (QALYs) presented as an incremental cost-effectiveness ratio (ICER). The results were also adjusted to international dollars (I$) using purchasing power parities (PPP) (1 I$ = 17.79 THB for the year 2013). The comparisons were between 1) an expanded neonatal screening programme using MS/MS screening for six prioritised diseases: phenylketonuria (PKU); isovaleric acidemia (IVA); methylmalonic acidemia (MMA); propionic acidemia (PA); maple syrup urine disease (MSUD); and multiple carboxylase deficiency (MCD); and 2) the current practice that is existing PKU screening. A comparison of the outcome and cost of treatment before and after clinical presentations were also analysed to illustrate the potential benefit of early treatment for affected children. A budget impact analysis was conducted to illustrate the cost of implementing the programme for 10 years. RESULTS: The ICER of neonatal screening using MS/MS amounted to 1,043,331 THB per QALY gained (58,647 I$ per QALY gained). The potential benefits of early detection compared with late detection yielded significant results for PKU, IVA, MSUD, and MCD patients. The budget impact analysis indicated that the implementation cost of the programme was expected at approximately 2,700 million THB (152 million I$) over 10 years. CONCLUSION: At the current ceiling threshold, neonatal screening using MS/MS in the Thai context is not cost-effective. However, the treatment of patients who were detected early for PKU, IVA, MSUD, and MCD, are considered favourable. The budget impact analysis suggests that the implementation of the programme will incur considerable expenses under limited resources. A long-term epidemiological study on the incidence of IEM in Thailand is strongly recommended to ascertain the magnitude of problem.

Establishing of National Birth Defects Registry in Thailand.

BACKGROUND: Deaths attributed to birth defects are a major cause of infant and under-five mortality as well as lifetime disabilities among those who survive. In Thailand, birth defects contribute to 21% of neonatal deaths. There is currently no systematic registry for congenital anomalies in Thailand. Queen Sirikit National Institute of Child Health has initiated a Thailand Birth Defects Registry to capture birth defects among newborn infants. OBJECTIVE: To establish the national birth defects registry in order to determine the burden of birth defects in Thailand. MATERIAL AND METHOD: The birth defects data come from four main sources: National Birth Registry Database; National Health Security Office's reimbursement database; Online Birth Defect Registry Database designed to capture new cases that were detected later; and birth defects data from 20 participated hospitals. All data are linked by unique 13-digit national identification number and International Classification of Diseases (ICD)-10 codes. This registry includes 19 common structural birth defects conditions and pilots in 20 hospitals. The registry is hospital-based, hybrid reporting system, including only live births whose information was collected up to 1 year of age. RESULTS: 3,696 infants out of 67,813 live births (8.28% of total live births in Thailand) were diagnosed with congenital anomalies. The prevalence rate of major anomalies was 26.12 per 1,000 live births. The five most common birth defects were congenital heart defects, limb anomalies, cleft lip/cleft palate, Down syndrome, and congenital hydrocephalus respectively. CONCLUSION: The present study established the Birth Defects Registry by collecting data from four databases in Thailand. Information obtained from this registry and surveillance is essential in the planning for effective intervention programs for birth defects. The authors suggest that this program should be integrated in the existing public health system to ensure sustainability.

Mutation spectrum of and founder effects affecting the PTS gene in East Asian populations.

The enzyme 6-pyruvoyl-tetrahydropterin synthase (PTPS, gene symbol: PTS) is involved in the second step of the de novo biosynthesis of tetrahydrobiopterin (BH4), which is a vital cofactor of nitric oxide synthases and three types of aromatic amino acid hydroxylases; the latter are important enzymes in the production of neurotransmitters. We conducted a study of PTS mutations in East Asia, including Taiwan, Mainland China, Japan, South Korea, the Philippines, Thailand and Malaysia. A total of 43 mutations were identified, comprising 22 previously reported mutations and 21 new discovered mutations. Among these, the c.155A>G, c.259C>T, c. 272A>G, c.286G>A and c.84-291A>G mutations were the most common PTS mutations in East Asia, while the c.58T>C and c.243G>A mutations were, respectively, specific to Filipinos and Japanese originating from Okinawa. Further studies demonstrated that each of the mutations listed above was in linkage disequilibrium to a specific allele of polymorphic microsatellite marker, D11S1347. These results suggest the presence of founder effects that have affected these frequent mutations in East Asia populations. In this context, D11S1347 should become one of the most reliable polymorphic markers for use in prenatal diagnosis among PTPS deficient families, especially where mutations are yet to be identified.

Maple syrup urine disease in Thai infants.

Maple syrup urine disease (MSUD) is a rare inborn error of metabolism, caused by a deficiency in activity of the branched chain alpha-keto acid dehydrogenase impairing the degradation of the branched-chain amino acids (leucine, isoleucine and valine). Classic MSUD usually manifests in the neonatal period with poor feeding, vomiting, lethargy, muscular hypertonicity, seizure, coma and death. Thirteen cases of classic MSUD were diagnosed from 1997-2007 at the Queen Sirikit National Institute of Child Health. All cases presented in the neonatal period. The onset of symptoms ranged from 3 to 20 days (median 8 days). The time taken to make the diagnosis ranged from 18 to 356 days (median 55 days). The diagnosis was accomplished by clinical diagnosis and confirmed by detecting abnormal levels of amino acids in the blood and organic acids in the urine. Clinical manifestations were non-specific such as poor suck, weak cry, drowsiness and seizures. Majority of cases were initially diagnosed as sepsis and/or meningitis. All patients had neurological sequelae and psychomotor retardation. This results show the need for increase awareness of metabolic disorder such as MSUD and the requirement for early detection and treatment to ensure a better outcome.

6-pyruvoyltetrahydropterin synthase deficiency two-case report.

6-Pyruvoyltetrahydropterin Synthase (PTPS) deficiency is the most common cause of hyperphenylalaninemia due to tetrahydrobiopterin deficiency. The presenting symptoms of PTPS deficiency are mental retardation, convulsions, disturbance of tone and posture, drowsiness, irritability, abnormal movements, hypersalivation, and swallowing difficulties(1-3). The authors reported the first two cases of PTPS deficiency in Thailand. Both cases were male infants who showed phenylalanine levels of 25.23 mg/dl and 23.4 mg/dl respectively. The urinary pterins analysis showed low biopterin and high neopterin. The percentage of urinary biopterin was also found to be very low. The mutation analysis of the first case revealed a point mutation of exon 4, a homozygous C to T transition at nucleotide 200 in codon 67 (T67M), and the second case showed a compound heterozygous of exon 4, C to A transition at nucleotide 200, and exon 5, C to T transition at nucleotide 259 of the PTS gene confirming that they had PTPS deficiency. Treatment was started with neurotransmitters and a low phenylalanine diet. Family carriers were detected by means of urinary pterins determination and mutation analysis.

Molecular diagnosis of Prader-Willi syndrome.

BACKGROUND: Prader-Willi syndrome (PWS) is characterized by neonatal hypotonia and feeding problems in infancy, developmental delay, hyperphagia with obesity, short stature, hypogonadism, characteristic facial appearance, and behavior problems. The diagnosis of PWS is based on clinical findings that change with age. PWS has proved to be a difficult condition to recognize with the diagnosis often being delayed until later childhood or even adulthood. Therefore, a molecular testing for PWS is needed to confirm the diagnosis. OBJECTIVE: To study the clinical features of Prader-Willi syndrome patients and confirm diagnosis by molecular testing. MATERIAL AND METHOD: Eighteen Prader-Willi syndrome patients who were diagnosed between March, 1997 and February, 2002 at the Genetic Unit, Queen Sirikit National Institute of Child Health, Bangkok. Peripheral blood lymphocytes were obtained and cultured using the standard technique for chromosome analysis. For fluorescence in situ hybridization (FISH) studies, the specific DNA probes for loci small nuclear ribonucleoprotein polypeptide N (SNRPN) were used to detect deletion. Non-deleted cases were confirmed to have PWS by methylation analysis. RESULTS: The diagnosis of eighteen PWS patients was confirmed by FISH using DNA probes for loci SNRPN demonstrating a deletion of chromosome 15q11-q13 in fourteen cases (77%). Four cases (23%) were confirmed to have PWS resulting from maternal uniparental disomy by demonstrating exclusively maternal specific DNA methylation patterns. CONCLUSION: The clinical diagnosis of PWS should be confirmed by molecular testing especially in the infancy period to avoid needless invasive diagnostic testing.

Phenylketonuria detected by the neonatal screening program in Thailand.

Neonatal screening for phenylketonuria (PKU) was introduced as a pilot project in Thailand from 1992--1995, and mass screening was started in 1996 by the Department of Medical Sciences, Ministry of Public Health. Blood samples were collected by heelprick on filter paper either at 48 hours of life or before discharge from the hospital. Elevated blood phenylalanine was identified by screening with the Guthrie method, then followed by the fluorometric method: All infants with a phenylalanine level equal to or greater than 4 mg/dl were recalled and retested using the fluorometric method and confirmed by plasma amino acid analysis and urinary pterins for tetrahydrobiopterin deficiency. A total of 1,062,676 newborns were screened from October 1992--March 2001, with 5 cases confirmed with PKU. The incidence was 1 in 212,535. All patients have been treated with low phenylalanine diet. The results of this study confirm the benefit of early detection and treatment of PKU through the screening program.