Publications by authors named "Sammy Pak-Lam Chen"

16 Publications

  • Page 1 of 1

Case Report: The first familial hCG syndrome in a Chinese family.

F1000Res 2021 8;10:458. Epub 2021 Jun 8.

Chemical Pathology Laboratory, Department of Pathology, Queen Elizabeth Hospital, Kowloon, Hong Kong.

Familial hCG syndrome is a rare and benign cause of elevated serum beta human chorionic gonadotropin (hCG). We present here a case of familial hCG syndrome diagnosed in a Hong Kong Chinese family, which we believe to be the first reported in Chinese. A 38-year-old woman presented with incidental finding of persistently elevated hCG, analytically confirmed both in urine and blood. Extensive radiological and biochemical work-up were performed but were negative for pregnancy and malignancy. Testing of another asymptomatic family member revealed unexplained elevation of serum hCG, confirming the diagnosis of familial hCG syndrome. Knowledge and awareness of this entity among clinicians are important to avoid unnecessary investigations and treatment in affected families.
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http://dx.doi.org/10.12688/f1000research.53636.1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8240598PMC
July 2021

In-house multiplex ligation-dependent probe amplification assay for citrin deficiency: analytical validation and novel exonic deletions in SLC25A13.

Pathology 2021 Dec 25;53(7):867-874. Epub 2021 May 25.

Kowloon West Cluster Laboratory Genetic Service, Chemical Pathology Laboratory, Department of Pathology, Princess Margaret Hospital, Hong Kong, China. Electronic address:

Citrin deficiency is one of the most common inborn errors of metabolism in East Asians, which may manifest as neonatal cholestasis, failure to thrive and dyslipidaemia, or recurrent hyperammonaemic encephalopathy. Its molecular diagnosis requires confirmation of the presence of biallelic pathogenic variants in SLC25A13 gene by sequencing, and analysis for a common insertion IVS16ins3kb. However, patients with compatible biochemical features but only one monoallelic pathogenic variant have remained a diagnostic challenge. Here we report the development, validation and application of a multiplex ligation-dependent probe amplification (MLPA) assay using an in-house oligonucleotide probemix and a customised Coffalyer.NET worksheet for detection of exonic copy number variations in SLC25A13. With this MLPA assay, we successfully identified the presence of a heterozygous exonic deletion in SLC25A13 in three of 15 (20%) unrelated individuals with only one monoallelic pathogenic variant detected using conventional methods. Three exonic deletions, two novel involving exon 14 and one reported involving exon 5, were subsequently confirmed with Sanger sequencing. In summary, we developed, evaluated, and demonstrated the clinical utility of an in-house MLPA assay to look for exonic deletions in SLC25A13 in patients with citrin deficiency. With the discovery of novel deletions, MLPA should be considered a test of choice for molecular diagnosis of citrin deficiency when the sequencing result is inconclusive.
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http://dx.doi.org/10.1016/j.pathol.2021.02.010DOI Listing
December 2021

Denosumab versus alendronate in long-term glucocorticoid users: A 12-month randomized controlled trial.

Bone 2021 05 23;146:115902. Epub 2021 Feb 23.

Department of Nuclear Medicine, Tuen Mun Hospital, Hong Kong.

Objectives: To compare the efficacy of denosumab and alendronate on raising spine bone mineral density (BMD) in long-term glucocorticoid (GC) users.

Methods: Adult patients receiving long-term prednisolone (≥2.5 mg/day for ≥1 year) were recruited and randomized to either subcutaneous denosumab (60 mg/6 months) or oral alendronate (70 mg/week). BMD (lumbar spine, femoral neck, hip) and bone markers (serum P1NP and CTX) were measured at month 0, 6 and 12. The difference in spine BMD (primary outcome) at month 12 was compared between the two groups.

Results: 139 subjects were recruited (age 50.0 ± 12.7 years; 96% women): 69 assigned denosumab and 70 assigned alendronate. At entry, 73(53%) patients were osteoporotic and 82(59%) patients were naive to the bisphosphonates. Baseline clinical characteristics and BMD values were similar in the two groups. At month 12, a significant gain in mean BMD at the lumbar spine (+3.5 ± 2.5%; p<0.001), hip (+0.9 ± 2.8%; p=0.01) and femoral neck (+1.04 ± 4.1%; p=0.047); was observed in denosumab-treated patients, whereas the corresponding change was +2.5 ± 2.9% (p<0.001), +1.6 ± 2.7% (p<0.001) and + 1.5 ± 3.9% (p=0.002) in the alendronate group. The spine, but not the hip or femoral neck, BMD at month 12 was significantly higher in the denosumab than alendronate group after adjustment for baseline BMD values, age, sex, osteoporosis risk factors and the cumulative prednisolone doses received in one year. The drop in P1NP and CTX was significantly higher in the denosumab than alendronate group. Frequency of adverse events (AEs), including infections, was similar in the two treatment arms. Seven patients withdrew from the study but not related to AEs.

Conclusions: In patients receiving long-term GCs, denosumab is superior to alendronate in raising the spine BMD after 12 months. Both drugs are well-tolerated.
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http://dx.doi.org/10.1016/j.bone.2021.115902DOI Listing
May 2021

Toxicity from illegitimate slimming agents - a 10-year case series at a tertiary toxicology laboratory in Hong Kong.

Clin Toxicol (Phila) 2021 May 22;59(5):426-432. Epub 2020 Sep 22.

Hospital Authority Toxicology Reference Laboratory, Princess Margaret Hospital, Kowloon, Hong Kong.

Context: This retrospective case-series study aims to provide an overview of the clinical, biochemical and analytical findings in patients who presented with toxicity related to the use of illegitimate slimming agents in Hong Kong from the perspective of a tertiary referral toxicology laboratory.

Methods: All clinical cases referred to the Hospital Authority Toxicology Reference Laboratory, Hong Kong with clinical suspicion of illegitimate slimming agent-related toxicity between January 2008 and December 2017 were reviewed retrospectively. The use of illegitimate slimming agents included the use of (1) deregistered slimming agents, (2) drug analogues that were not registered drugs, (3) registered drugs not approved for the indication of weight reduction (whether prescribed by a doctor or not), and (4) prescription-only slimming agents without a doctor's prescription. Patients taking registered weight-reducing drugs prescribed by a doctor were excluded. Patient demographics, clinical features, relevant laboratory investigations, and toxicological findings were analyzed.

Results: From 2008 to 2017, a total of 346 patients were analytically confirmed by our laboratory to have clinical toxicity related to the use of illegitimate slimming agents. The median age of the patients was 27 years and 92.5% of the patients were female. The most common clinical presentations included psychiatric features, sympathomimetic toxicity, hypokalemia, and abnormal thyroid function tests. Fatal or severe clinical toxicity was observed in 10% of the cases. The major classes of drugs detected on our analytical platforms were stimulants (e.g., sibutramine), laxatives (e.g., anthraquinones), diuretics (e.g., hydrochlorothiazide), and thyroid hormones (e.g., animal thyroid tissue). These illegitimate slimming agents were obtained from various sources including the Internet, over-the-counter in community pharmacy, or unspecified local sources.

Discussion And Conclusions: The use of slimming agents is common worldwide; apart from taking registered slimming agents prescribed by registered practitioners, many users obtain slimming agents from various illegitimate sources. The unregulated use of these drugs can be associated with significant clinical toxicity. This study provides a current landscape of illegitimate slimming agent toxicity in Hong Kong to frontline clinicians and other toxicology professionals. Collaboration between clinicians, laboratories, and government authorities would be imperative to prevent further health adversities related to the misuse of these agents.
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http://dx.doi.org/10.1080/15563650.2020.1822529DOI Listing
May 2021

Determination of cerebrospinal fluid adenosine deaminase activity cut-off for the diagnosis of tuberculous meningitis in Hong Kong.

J Clin Pathol 2020 Dec 18;73(12):800-802. Epub 2020 May 18.

Chemical Pathology Laboratory, Department of Pathology, Princess Margaret Hospital, Kowloon, Hong Kong.

Aims: Tuberculous meningitis (TBM) is a severe infection which may lead to serious complication and mortality. Prompt diagnosis and treatment are essential. There is a need for a simple and fast laboratory test to differentiate TBM from other causes.

Methods: Retrospective review was conducted for cerebrospinal fluid adenosine deaminase (CSF-ADA) activity which was measured at the Chemical Pathology Laboratory of Princess Margaret Hospital, the sole centre providing such service in Hong Kong, for 51 patients with suspected meningitis from nine local hospitals between June 2014 and July 2017. TBM diagnosis was defined by positive culture and/or nucleic acid amplification test result of complex in CSF.

Results: CSF-ADA activity was significantly higher in the TBM group (8.6±2.1 IU/L, n=8) than that of the non-TBM group (2.8±5.9 IU/L, n=43). The optimal clinical cut-off of 5.1 U/L for TBM diagnosis in our laboratory yielded 100% sensitivity, 91% specificity, positive likelihood ratio of 10.8 and negative likelihood ratio of 0. In rare circumstance, false elevation may be seen in non-tuberculous cause, such as central nervous system lymphoma and fungal infection.

Conclusions: We recommend the use of CSF-ADA activity, which is a simple, fast and robust test for early differentiation of TBM from other causes, to facilitate timely initiation of antituberculous treatment and potentially improve patients' outcome.
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http://dx.doi.org/10.1136/jclinpath-2019-206397DOI Listing
December 2020

Case Report: The first probable Hong Kong Chinese case of -related acute recurrent rhabdomyolysis in a boy with two novel variants.

F1000Res 2019 2;8:1566. Epub 2019 Sep 2.

Kowloon West Cluster Laboratory Genetic Service, Chemical Pathology Laboratory, Department of Pathology, Princess Margaret Hospital, Hong Kong, Laichikok, Hong Kong.

Recurrent rhabdomyolysis is frequently ascribed to fatty acid ß-oxidation defects, mitochondrial respiratory chain disorders and glycogen storage-related diseases. In recent years, autosomal recessive mutations have been identified as a prevailing cause of severe rhabdomyolysis in children in Western countries. We report the first probable Hong Kong Chinese case of recurrent severe rhabdomyolysis in early childhood caused by variants. Compound heterozygous novel variants NM_145693.2(LPIN1):c.[1949_1967dupGTGTCACCACGCAGTACCA]; [2410G>C] (p.[Gly657Cysfs*12];[Asp804His]) were detected. The former variant was classified as likely pathogenic while the latter variant was classified as a variant of uncertain significance (VUS) based on the guideline published by the American College of Medical Genetics and Genomics (ACMG) in 2015. Although the genetic findings were inconclusive, the patient's presentation was compatible with LPIN1-related acute recurrent rhabdomyolysis, and the patient was treated as such. The early recognition, timely diagnosis and management of this condition are important to avoid fatal consequences. To our knowledge, there has been no previous report in the English-language literature of a child with Chinese ethnicity and -related acute recurrent rhabdomyolysis (MIM #268200).  Functional characterization of the novel variants detected in this study are warranted in future studies.
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http://dx.doi.org/10.12688/f1000research.20343.1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6823901PMC
June 2020

Founder Mutation c.1516A>C in KLHL40 Is a Frequent Cause of Nemaline Myopathy With Hyponatremia in Ethnic Chinese.

J Neuropathol Exp Neurol 2019 09;78(9):854-864

Department of Pathology, Princess Margaret Hospital.

KLHL40-related nemaline myopathy is a severe autosomal recessive muscle disorder. The current study describes 4 cases of KLHL40-related nemaline myopathy in Hong Kong ethnic Chinese presenting within 3 years, which are confirmed with clinicopathologic features and genetic studies. The incidence is estimated to be at least 1 in 45 226 livebirths (at least 1 in 41 608 among ethnic Chinese livebirths) in Hong Kong. Hyponatremia appears to be another common feature in these patients. Salient histological features include nemaline bodies ranging from 200 to 500 nm in diameters on ultrastructural examination as well as negative KLHL40 immunohistochemistry; type II fiber predominance is obvious in 2 cases. We demonstrate the founder effect associated with genetic variant c.1516A>C (p.Thr506Pro) by polymorphic marker analysis, which revealed a 0.56-0.75-Mb or 0.41-0.78-cM shared haplotype encompassing the disease allele. The mutation is believed to have occurred around 412 generations ago or 6220 BCE, as estimated using DMLE+ and a formula described by Boehnke. We believe the founder variant might possibly underlie a sizable portion of nemaline myopathy in ethnic Chinese. Analysis of the KLHL40 gene may be considered as the first-tier testing of congenital myopathy in this ethnic group.
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http://dx.doi.org/10.1093/jnen/nlz056DOI Listing
September 2019

Adulteration of proprietary Chinese medicines and health products with undeclared drugs: experience of a tertiary toxicology laboratory in Hong Kong.

Br J Clin Pharmacol 2018 Jan 4;84(1):172-178. Epub 2017 Oct 4.

Hospital Authority Toxicology Reference Laboratory, Princess Margaret Hospital, Hong Kong.

Aims: Proprietary Chinese medicines (pCMs) and health products, generally believed to be natural and safe, are gaining popularity worldwide. However, the safety of pCMs and health products has been severely compromised by the practice of adulteration. The current study aimed to examine the problem of adulteration of pCMs and health products in Hong Kong.

Methods: The present study was conducted in a tertiary referral clinical toxicology laboratory in Hong Kong. All cases involving the use of pCMs or health products, which were subsequently confirmed to contain undeclared adulterants, from 2005 to 2015 were reviewed retrospectively.

Results: A total of 404 cases involving the use of 487 adulterated pCMs or health products with a total of 1234 adulterants were identified. The adulterants consisted of approved drugs, banned drugs, drug analogues and animal thyroid tissue. The six most common categories of adulterants detected were nonsteroidal anti-inflammatory drugs (17.7%), anorectics (15.3%), corticosteroids (13.8%), diuretics and laxatives (11.4%), oral antidiabetic agents (10.0%) and erectile dysfunction drugs (6.0%). Sibutramine was the most common adulterant (n = 155). The reported sources of these illicit products included over-the-counter drug stores, the internet and Chinese medicine practitioners. A significant proportion of patients (65.1%) had adverse effects attributable to these illicit products, including 14 severe and two fatal cases. Psychosis, iatrogenic Cushing syndrome and hypoglycaemia were the three most frequently encountered adverse effects.

Conclusions: Adulteration of pCMs and health products with undeclared drugs poses severe health hazards. Public education and effective regulatory measures are essential to address the problem.
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http://dx.doi.org/10.1111/bcp.13420DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5736835PMC
January 2018

Improvement of bone mineral density after enzyme replacement therapy in Chinese late-onset Pompe disease patients.

BMC Res Notes 2017 Jul 28;10(1):351. Epub 2017 Jul 28.

Department of Radiology, Princess Margaret Hospital, Kowloon, Hong Kong SAR.

Objective: Late-onset Pompe disease (LOPD) is a lysosomal storage disease resulted from deficiency of the enzyme acid α-glucosidase. Patients usually develop a limb-girdle pattern of myopathy and respiratory impairment, and enzyme replacement therapy (ERT) is the only specific treatment available. Recently, LOPD has been associated with low bone mineral density (BMD), but the effect of ERT on BMD is inconclusive. In this report we described our early observations on the change of BMD after ERT in Chinese LOPD patients.

Results: We studied four Chinese LOPD patients with different severities of myopathy. All were underweight, and three had osteoporosis at baseline. We found significant weight gain in three patients after ERT and all four patients showed improvement in BMD. The biggest improvement, 84.4% increase in BMD, was seen in a lady with the most prominent weight recovery. Our results suggest that ERT improves BMD in Chinese LOPD and weight gain could be a major contributor to this effect.
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http://dx.doi.org/10.1186/s13104-017-2681-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5534128PMC
July 2017

NMR-based urinalysis for rapid diagnosis of β-ureidopropionase deficiency in a patient with Dravet syndrome.

Clin Chim Acta 2015 Feb 25;440:201-4. Epub 2014 Oct 25.

Department of Pathology, Princess Margaret Hospital, Hong Kong, China.

Background: Beta-ureidopropionase deficiency is a rare inborn error of metabolism (IEM) affecting pyrimidine metabolism. To-date, about 30 genetically confirmed cases had been reported. The clinical phenotypes of this condition are variable; some patients were asymptomatic while some may present with developmental delay or autistic features. In severe cases, patients may present with profound neurological deficit including hypotonia, seizures and mental retardation. Using NMR-based urinalysis, this condition can be rapidly diagnosed within 15 min.

Case: An 11-month-old Chinese boy had dual molecular diagnoses, β-ureidopropionase deficiency and Dravet syndrome. He presented with intractable and recurrent convulsions, global developmental delay and microcephaly. Urine organic acid analysis using GC-MS and NMR-based urinalysis showed excessive amount of β-ureidopropionic acid and β-ureidoisobutyric acid, the two disease-specific markers for β-ureidopropionase deficiency. Genetic analysis confirmed homozygous known disease-causing mutation UPB1 NM_016327.2: c.977G>A; NP_057411.1:p.R326Q. In addition, genetic analysis for Dravet syndrome showed the presence of heterozygous disease-causing mutation SCN1A NM_001165963.1:c.4494delC; NP_001159435.1:p.F1499Lfs*2.

Conclusions: The differentiation between Dravet syndrome and β-ureidopropionase deficiency is clinically challenging since both conditions share overlapping clinical features. The detection of urine β-ureidoisobutyric and β-ureidopropionic acids using NMR or GC-MS is helpful in laboratory diagnosis of β-ureidopropionase deficiency. The disease-causing mutation, c.977G>A of β-ureidopropionase deficiency, is highly prevalent in Chinese population (allele frequency=1.7%); β-ureidopropionase deficiency screening test should be performed for any patients with unexplained neurological deficit, developmental delay or autism.
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http://dx.doi.org/10.1016/j.cca.2014.10.030DOI Listing
February 2015

Electronic chemical pathology consultation service and dried blood spot metabolic screening in hospital patients.

J Clin Pathol 2012 Dec 10;65(12):1141-5. Epub 2012 Aug 10.

Chemical Pathology Laboratory, Department of Pathology, Princess Margaret Hospital, Hong Kong SAR, China.

Aim: Inborn errors of metabolism (IEM) are an unpopular and difficult subject and most clinicians are unfamiliar with them. Although chemical pathologists have a long-standing practice in advising test strategy and result interpretation especially from primary care, such consultations are usually informal, unstructured and those related to IEM are infrequently requested. This study aims to provide a formal electronic consultation service and to apply tandem mass spectrometry-based dried blood spot metabolic screening (DBSM) as a rapid first-line test for patients suspected of IEM.

Methods: DBSM and a chemical pathology consultation were ordered through the hospital computer terminals. DBSM detected 29 metabolic disorders. The clinical data and metabolic results for the 12-month period were reviewed.

Results: There were 279 consultations of which 209 were initiated by paediatricians and 70 by adult physicians. The main reasons for consultation were developmental delay, neurological abnormalities, unexplained biochemical abnormalities and monitoring of patients with IEM. There were 158 DBSM requests. One positive case of isovaleric acidaemia was detected.

Conclusions: All high-risk paediatric patients should have a DBSM and a timely electronic chemical pathology consultation as a rapid and cost-effective first-line screening. Provision of a visible, accessible and helpful consultation service enables professional reimbursement.
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http://dx.doi.org/10.1136/jclinpath-2012-200837DOI Listing
December 2012

Measurement of yunaconitine and crassicauline A in small-volume blood serum samples by LC-MS/MS: tracing of aconite poisoning in clinical diagnosis.

Talanta 2012 Aug 31;97:491-8. Epub 2012 May 31.

Toxicology Reference Laboratory, Department of Pathology, Princess Margaret Hospital, Lai Chi Kok, Kowloon, Hong Kong Special Administrative Region.

Aconite poisoning is one of the most serious types of herb-related medical emergencies. In Hong Kong, many if not most of these poisoning cases are due to confusion in herbal species; that is, the wrong herbs are used in prescriptions. Such human errors, while inevitable perhaps, can be serious, and sometimes fatal. The chemical components responsible for aconite poisoning are yunaconitine and crassicauline A. In the present study, a rapid and sensitive method for the screening and quantification of yunaconitine and crassicauline A in human serum, using LC-MS/MS, was developed and validated. Methyllycaconitine was chosen as the internal standard. The limit of detection (LOD) of yunaconitine and crassicauline A were found to be 0.022 and 0.021 ng/mL, respectively. The limit of quantification (LOQ) was 0.1 ng/mL for both yunaconitine and crassicauline A. The recovery of yunaconitine and crassicauline A ranged from 78.6% to 84.9% and 78.3% to 87.2%, respectively. The matrix effect of yunaconitine and crassicauline A ranged from 110.0% to 130.4% and 121.2 to 130.0%, respectively. Both yunaconitine and crassicauline A were stable in serum for at least 3 months at -20 °C, and the extracts were stable for at least 7 days. For clinical applications, serum samples of two patients confirmed to have had aconite herbs poisoning in 2008 were quantified using the developed method. The result showed that this method can be utilized in clinical routine applications. This screening method expedites the diagnosis in cases of suspected aconite poisoning, thus enabling doctors to treat the condition more quickly and effectively.
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http://dx.doi.org/10.1016/j.talanta.2012.05.004DOI Listing
August 2012

Aconite poisoning over 5 years: a case series in Hong Kong and lessons towards herbal safety.

Drug Saf 2012 Jul;35(7):575-87

Hospital Authority Toxicology Reference Laboratory, Princess Margaret Hospital, Hospital Authority, Hong Kong.

Background: Aconite poisoning is a severe, life-threatening poisoning related to the use of traditional Chinese medicine (TCM). Despite current legislation, repeated poisoning cases are steadily encountered.

Objective: The aim of the study was to summarize the clinical features and to elucidate the causative and contributory factors leading to aconite poisoning.

Methods: This study was conducted within the Hospital Authority Toxicology Reference Laboratory, which is the sole tertiary referral clinical toxicology laboratory in Hong Kong. This retrospective study reviewed all confirmed aconite poisoning cases handled by a clinical toxicology laboratory between April 2004 and July 2009. The diagnosis in all cases was confirmed biochemically by detecting aconitum alkaloids in urine specimens. Additionally, herbal specimens were morphologically identified and herbal formulae were studied and transcribed. The cause of poisoning for each case was determined whenever possible.

Results: Fifty-two cases were examined in this aconite poisoning case series. Neurological, cardiovascular and gastrointestinal toxicities were encountered in 49 (94.2%), 46 (88.5%) and 31 (59.6%) patients, respectively. The poisoning was severe in 6 (11.5%) patients, moderate in 17 (32.7%) patients and mild in 29 (55.8%) patients. Amongst 44 patients (84.6%) in whom the underlying reasons of poisoning could be determined, four major causes were found. These included overdose - prescription of a higher than recommended dosage of aconite herbs in 17 (32.7%) cases; 'hidden' poisoning (the aconite herb was not prescribed but dispensed inadvertently) in 17 (32.7%) cases; usage of inadequately processed herbs in 7 (13.5%) cases; and dispensary error in 2 (3.9%) cases. No case fatality was recorded.

Conclusion: In the majority of cases in this series, the causes of poisoning can be traced to poor-quality herbs, poor quality of prescription practice, or dispensary errors. The quality issues of TCM practice should be critically addressed to minimize this poisoning threat.
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http://dx.doi.org/10.2165/11597470-000000000-00000DOI Listing
July 2012

Phenylketonuria in Hong Kong Chinese: a call for hyperphenylalaninemia newborn screening in the Special Administrative Region, China.

Chin Med J (Engl) 2011 Aug;124(16):2556-8

Kowloon West Cluster Laboratory Genetic Service, Chemical Pathology Laboratory, Department of Pathology, Princess Margaret Hospital, Hong Kong, China.

Hyperphenylalaninemia is one of the commonest inborn errors of metabolism affecting approximately 1 in 15,000 livebirths. Among Chinese, BH4 deficiency leading to hyperphenylalaninemia is much commoner than in Caucasians. Exact diagnosis is important for the treatment and genetic counseling. In 2000, newborn screening for phenylketonuria is mandatory by law in China throughout the whole country. However, it is not yet included in the newborn screening program of the Hong Kong Special Administrative Region, China. Published data on hyperphenylalaninemia among HongKong Chinese are largely lacking. We report a 1-year-old Hong Kong Chinese girl with severe 6-pyruvoyl-tetrahydropterin synthase (PTPS) deficiency. The patient presented with infantile hypotonia and was misdiagnosed as cerebral palsy. She had very mild hyperphenylalaninemia (95 μmol/L), significantly high phenylalnine-to-tyrosine ratio (3.1), and elevated prolactin of 1109 mIU/L. Genetic analysis confirmed a homozygous known disease-causing mutation PTS NM_000317.1:c.259C>T; NP_000308.1: p.P87S in the proband. In our local experience, while the estimated prevalence of hyperphenylalaninemia due to PTPS deficiency was reported to be 1 in 29,542 live births, not a single case of phenylalanine hydroxylase deficiency has been reported. Furthermore, there is a general lack of awareness of inherited metabolic diseases in the community as well as among the medical professionals. Very often, a low index of clinical suspicion will lead to delay in diagnosis, multiple unnecessary and costly investigations, prolonged morbidity and anxiety to the family affected. We strongly recommend that expanded newborn screening for hyperphenylalaninemia should be implemented for every baby born in the Hong Kong Special Administrative Region, China.
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August 2011

Analysis of inborn errors of metabolism: disease spectrum for expanded newborn screening in Hong Kong.

Chin Med J (Engl) 2011 Apr;124(7):983-9

Chemical Pathology Laboratory, Department of Pathology, Princess Margaret Hospital, Hong Kong SAR, China.

Background: Data of classical inborn errors of metabolism (IEM) of amino acids, organic acids and fatty acid oxidation are largely lacking in Hong Kong, where mass spectrometry-based expanded newborn screening for IEM has not been initiated. The current study aimed to evaluate the approximate incidence, spectrum and other characteristics of classical IEM in Hong Kong, which would be important in developing an expanded newborn screening program for the local area.

Methods: The laboratory records of plasma amino acids, plasma acylcarnitines and urine organic acids analyses from year 2005 to 2009 inclusive in three regional chemical pathology laboratories providing biochemical and genetic diagnostic services for IEM were retrospectively reviewed.

Results: Among the cohort, 43 patients were diagnosed of IEM, including 30 cases (69%) of amino acidemias (predominantly citrin deficiency, hyperphenylalaninemia due to 6-pyruvoyl-tetrahydropterin synthase deficiency and tyrosinemia type I), 5 cases (12%) of organic acidemias (predominantly holocarboxylase synthetase deficiency) and 8 cases (19%) of fatty acid oxidation defects (predominantly carnitine-acylcarnitine translocase deficiency). The incidence of classical IEM in Hong Kong was roughly estimated to be at least 1 case per 4122 lives births, or 0.243 cases per 1000 live births. This incidence is similar to those reported worldwide, including the mainland of China. The estimated incidence of hyperphenylalaninemia was 1 in 29 542 live births.

Conclusions: Our data indicate that it is indisputable for the introduction of expanded newborn screening program in Hong Kong. Since Hong Kong is a metropolitan city, a comprehensive expanded newborn screening program and referral system should be available to serve the neonates born in the area.
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April 2011
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