Kwang-Jen Hsiao

Nationwide survey of extended newborn screening by tandem mass spectrometry in Taiwan

In Taiwan, during the period March 2000 to June 2009, 1,495,132 neonates were screened for phenylketonuria (PKU) and homocystinuria (HCU), and 1,321,123 neonates were screened for maple syrup urine disease (MSUD), methylmalonic academia (MMA), medium-chain acyl-coenzyme A (CoA) dehydrogenase (MCAD) deficiency, isovaleric academia (IVA), and glutaric aciduria type 1 (GA-1) using tandem mass spectrometry (MS/MS). In a pilot study, 592,717 neonates were screened for citrullinemia, 3-methylcrotonyl-CoA carboxylase deficiency (3-MCC) and other fatty acid oxidation defects in the MS/MS newborn screening. A total of 170 newborns and four mothers were confirmed to have inborn errors of metabolism. The overall incidence was approximately 1/5,882 (1/6,219 without mothers). The most common inborn errors were defects of phenylalanine metabolism [five classic PKU, 20 mild PKU, 40 mild hyperphenylalaninemia (HPA), and 13 6-pyruvoyl-tetrahydropterin synthase (PTPS) deficiency]. MSUD was the second most common amino acidopathy and, significantly, most MSUD patients (10/13) belonged to the Austronesian aboriginal tribes of southern Taiwan. The most frequently detected among organic acid disorders was 3-MCC deficiency (14 newborns and four mothers). GA-1 and MMA were the second most common organic acid disorders (13 and 13 newborns, respectively). In fatty acid disorders, five carnitine transport defect (CTD), five short-chain acyl-CoA dehydrogenase deficiency (SCAD), and two medium-chain acyl-CoA dehydrogenase (MCAD) deficiency were confirmed. This is the largest case of MS/MS newborn screening in an East-Asian population to date. We hereby report the incidences and outcomes of metabolic inborn error diseases found in our nationwide MS/MS newborn screening program.

Frequency and distribution in East Asia of 12 mutations identified in the SLC25A13 gene of Japanese patients with citrin deficiency

AbstractDeficiency of citrin, a liver-type mitochondrial aspartate-glutamate carrier (AGC), encoded by the SLC25A13 gene on chromosome 7q21.3, causes autosomal recessive disorders: adult-onset type II citrullinemia (CTLN2) and neonatal hepatitis associated with intrahepatic cholestasis (NICCD). So far, we have described 12 SLC25A13 mutations: 11 were from Japan and one from Israel. Three mutations found in Chinese and Vietnamese patients were the same as those in Japanese patients. In the present study, we identified a novel mutation IVS6+1G>C in a Japanese CTLN2 patient and widely screened 12 SLC25A13 mutations found in Japanese patients in control individuals from East Asia to confirm our preliminary results that the carrier frequency was high in Asian populations. Mutations 851-854del and 1638-1660dup were found in all Asian countries tested, and 851-854del associated with 290-haplotype in microsatellite marker D7S1812 was especially frequent. Other mutations frequently detected were IVS11+1G>A in Japanese and Korean, S225X in Japanese, and IVS6+5G>A in Chinese populations. We found a remarkable difference in carrier rates in China (including Taiwan) between north (1/940) and south (1/48) of the Yangtze River. We detected many carriers in Chinese (64/4169 = 1/65), Japanese (20/1372 = 1/69) and Korean (22/2455 = 1/112) populations, suggesting that over 80,000 East Asians are homozygotes with two mutated SLC25A13 alleles.

Screening of nine SLC25A13 mutations: their frequency in patients with citrin deficiency and high carrier rates in Asian populations

Deficiency of citrin encoded by SLC25A13 causes adult-onset type II citrullinemia (CTLN2) and idiopathic neonatal hepatitis (NICCD). So far we have diagnosed 126 (3) CTLN2 and 103 (4) NICCD patients in Japan (and other countries). From preliminary population analysis of the known nine SLC25A13 mutations, we found that the carrier frequency is high in China (1/79), Taiwan (1/98), and Korea (1/50) as well as Japan (1/69), suggesting that many patients with citrin deficiency exist in East Asia.

Mutation spectrum of MMACHC in Chinese patients with combined methylmalonic aciduria and homocystinuria.

The cblC type of combined methylmalonic aciduria (MMA) and homocystinuria (HC) is the most common inborn error of vitamin B12 metabolism and is caused by mutations in the MMACHC gene. To elucidate the spectrum of mutations that causes combined MMA and HC in Chinese patients, the MMACHC gene was sequenced in 79 unrelated Chinese patients. Sequence analysis identified 98.1% of disease alleles and found that all patients had at least one MMACHC mutation. A total of 24 mutations were identified. Out of the 24 mutations identified, 9 were novel ones, including missense mutations (c.365A>T and c.452A>G), nonsense mutations (c.315C>G and c.615C>A), deletions (c.99delA and c.277-3_c.303del30), duplications (c.248dupT and c.626dupT) and an insertion (c.445_446insA). The c.609G>A, c.658_660delAAG, c.482G>A, c.394C>T and c.80A>G mutations were the most common mutations and accounted for 80% of disease alleles. Haplotype analysis suggests that the spread of the c.80A>G, c.609G>A and c.658_660delAAG mutations in Chinese patients were caused by a founder effect. The results indicate that defects occurring in the MMACHC gene are the major cause of this disease in Chinese patients with combined MMA and HC, and direct mutation analysis can therefore be used as a rapid confirmatory diagnosis among these Chinese patients.

Tetrahydrobiopterin-deficient hyperphenylalaninemia in the Chinese

BACKGROUNDnHyperphenylalaninemia (HPA) may be caused by either a deficiency in phenylalanine-4-hydroxylase or in tetrahydrobiopterin (BH4), the essential cofactor required for the hydroxylation of aromatic amino acids. The most common forms of BH4 deficiency are 6-pyruvoyl-tetrahydropterin synthase (PTPS) deficiency (MIM 261640) and dihydropteridine reductase (DHPR) deficiency (MIM 261630), which require a different treatment from classical HPA.nnnRESULTSnApproximately 86% of BH4-deficient HPA in the Chinese population was found to be caused by PTPS deficiency. Eleven missense (73C-->G, 120T-->G, 155A-->G, 166G-->A, 200C-->T, 209T-->A, 226C-->T, 259C-->T, 286G-->A, 317C-->T, 430G-->C), one splicing (IVS3+1G-->A) and two deletion mutations (116-119delTGTT, 169-171delGTG) were identified in 37 unrelated PTPS-deficient Chinese families. Among these, 155A-->G, 259C-->T and 286G-->A mutation accounted for about 80% of the mutant alleles. The 155A-->G and 286G-->A mutations were found to be the common mutation in southern and northern Chinese, respectively. Only two Chinese DHPR-deficient families were detected among about 300 Chinese hyperphenylalaninemia cases. A single base transition 508G-->A on the DHPR cDNA was identified in two consanguineous DHPR-deficient siblings. A reduced level of DHPR mRNA expression was found in the other DHPR-deficient patient, which suggested that the mutation might lie in the regulatory region of the DHPR gene.nnnCONCLUSIONSnThe BH4-deficient HPA was estimated to make up around 30% of the Chinese population in Taiwan suffering from HPA, which is much higher than in Caucasian populations (1.5-2% of HPA).

Suggestive linkage of familial primary cutaneous amyloidosis to a locus on chromosome 1q23

Backgroundu2002 There is a high incidence of primary cutaneous amyloidosis (PCA) in South America, South‐east Asia and Taiwan. To date, the aetiology of PCA remains unknown, but it is believed to be multifactorial. Although most cases are sporadic, some patients have a family history. Familial aggregation and different susceptibility to PCA among ethnic groups suggest that genetic factors may play an important role in its pathogenesis. However, no genetic loci for familial PCA (FPCA) have been identified so far.

Mutation Profile of the MUT Gene in Chinese Methylmalonic Aciduria Patients

The mut-type methylmalonic aciduria (MMA, MIM 251000) is caused by a deficiency of mitochondrial methylmalonyl-CoA mutase (MCM, E.C. 5.4.99.2) activity, which results from defects in the MUT gene. To elucidate the mutation spectrum of the MUT gene in Chinese MMA patients, 13 exons of the MUT gene, including untranslated regions, were analyzed by PCR-based sequencing for 42 unrelated Chinese MMA patients. All the 42 patients were found to have at least one MUT mutation. A total of 41 mutations were identified. Of these mutations, 20 were novel ones, including one nonsense mutation (c.103C>T), 12 missense mutations (c.316A>C, c.424A>G, c.494A>G, c.554C>T, c.599T>C, c.919T>C, c.1009T>C, c.1061C>T, c.1141G>A, c.1208G>A, c.1267G>A, and c.1295A>C), one duplication (c.755dupA), three small deletions (c.398_399delGA, c.1046_1058del, and c.1835delG), two mutations that might affect mRNA splicing (c.754-1G>A and c.1084-10A>G), and one major deletion. Among the mutations identified, the c.1280G>A (15.5%), c.729_730insTT (10.7%), c.1106G>A (4.8%), c.1630_1631GG>TA (4.8%), and c.2080C>T (4.8%) accounted for 40% of the diseased alleles. The c.1280G>A and c.729_730insTT mutations were found to be the most frequent mutations in Southern and Northern Chinese, respectively. The results of microsatellite analysis suggest that the spread of c.729_730insTT among the Northern Chinese and of c.1280G>A and c.1630_1631GG>TA among the Southern Chinese may have undergone founder effects. This mutation analysis of the gene responsible for mut-type MMA will help to provide a molecular diagnostic aid for differential diagnosis of MMA and could be applied for carrier detection and prenatal diagnosis among Chinese family at risk of mut-type MMA.

The universal newborn hearing screening program of Taipei City

OBJECTIVESnTo establish a hearing screening program with high coverage, low referral rate, high follow-up rate, and early intervention in Taipei City.nnnMETHODSnFrom September 2009 to December 2010, 85% delivery units in Taipei City, which includes 20 hospitals and 14 obstetrics clinics, were recruited into the screening program in two stages. A total of 15,930 babies were born in these participating hospitals and clinics during the program period. Among these neonates, 15,790 underwent hearing screening test with automatic auditory brainstem response (AABR). The screening was free of charge to the parents. The hearing screening examination was performed 24-36 h after birth. The same test was repeated between 36 and 60 h of age if the baby failed the first hearing test. The neonate was referred to the diagnostic hospitals for further investigations if he failed the second test.nnnRESULTSnThe screening coverage rate was 99.1% (15,790/15,930). The incidence of bilateral moderate to severe and unilateral hearing loss was 1.4 per 1000 (22/15,790) and 1.5 per 1000 (24/15,790), respectively. Four percent (626/15,790) of newborns failed to pass the initial screening test and 1.0% of newborns failed to pass the second screening test. Therefore, 1.0% newborns were referred for diagnostic assessments. The follow-up rate was 94.4% (151/160). Sixty-four percent (14/22) of babies with bilateral hearing loss completed the full diagnostic hearing tests within 3 months of birth.nnnCONCLUSIONSnThe universal newborn hearing screening program is an adequate program for Taipei City with high coverage, low referral rate, and good follow-up rate. Screening fees covered by third parties, two-stage screening steps with AABR strategy, and the stringent monitoring system proved to be effective.nnnLEVEL OF EVIDENCEn2b, individual cohort study.

Long-term Follow-up of Taiwanese Chinese Patients Treated Early for 6-Pyruvoyl-Tetrahydropterin Synthase Deficiency

OBJECTIVEnTo report the long-term results of early initiation of treatment of 6-pyruvoyl-tetrahydropterin synthase (PTPS) deficiency.nnnDESIGNnBetween 1988 and 2000, 12 newborns with PTPS deficiency who underwent early treatment at our hospital were identified. All patients received tetrahydrobiopterin replacement in a daily dosage between approximately 2 and 4 mg/kg. The dosages of levodopa replacement were 10 to 15 mg/kg/d, which is considerably higher than the typically recommended dosages of less than 7 mg/kg/d for patients aged younger than 2 years and 8 to 10 mg/kg/d for patients aged 2 years or older. Replacement with 5-hydroxytryptophan varied widely among patients.nnnSETTINGnTaipei Veterans General Hospital. Patients Twelve newborns.nnnINTERVENTIONSnTreatment with tetrahydrobiopterin, levodopa, and 5-hydroxytryptophan. Main Outcome Measure IQ score.nnnRESULTSnThe mean (SD) IQ score of our PTPS-deficient patients was 96.7 (9.7; range 86-119), which is considerably higher than previous reports of other populations of PTPS-deficient patients. All patients reached a normal IQ on high daily dosages of levodopa replacement, without developing apparent long-term levodopa-induced adverse effects. We also observed a correlation between long-term IQ score and genotype, birth weight, and age at initiation of treatment.nnnCONCLUSIONSnAn effective newborn screening referral program and early initiation of appropriate therapy preserved the IQ scores of PTPS-deficient patients.

Newborn Screening for Methylmalonic Aciduria by Tandem Mass Spectrometry: 7 Years' Experience From Two Centers in Taiwan

Background: The clinical course of methylmalonic aciduria (MMA) is fulminant in neonates and emergency management is necessary to save lives. It is therefore very important to differentiate affected from unaffected neonates immediately when there are abnormal results regarding MMA in newborn screening. Methods: Between January 2002 and December 2008, 598,522 newborns were screened for MMA by 2 neonatal screening centers: the Chinese Foundation of Health and the Taipei Institute of Pathology. A total of 22 newborns were referred to confirmatory medical centers, and 7 were confirmed as having MMA. The initial propionylcarnitine (C3) level, C3/acetylcarnitine (C2) ratio, plasma ammonia, liver function tests, blood pH and bicarbonate were compared between the true‐positive and false‐positive groups. Results: The C3/C2 ratio and plasma ammonia were markedly higher in the true‐positive MMA group (p < 0.0001). Blood gas pH (p = 0.029), bicarbonate (p = 0.019), and aspartate aminotransferase (p = 0.005) also significantly differed between these 2 groups. Conclusion: Referred newborns with elevated plasma C3/C2 ratios > 0.4 or ammonia levels > 200 mg/dL should be highly suspected of having MMA.