A metabolic signature for NADSYN1-dependent congenital NAD deficiency disorder

Nicotinamide adenine dinucleotide (NAD) is essential for embryonic development. To date, biallelic loss-of-function variants in 3 genes encoding nonredundant enzymes of the NAD de novo synthesis pathway - KYNU, HAAO, and NADSYN1 - have been identified in humans with congenital malformations defined as congenital NAD deficiency disorder (CNDD). Here, we identified 13 further individuals with biallelic NADSYN1 variants predicted to be damaging, and phenotypes ranging from multiple severe malformations to the complete absence of malformation. Enzymatic assessment of variant deleteriousness in vitro revealed protein domain-specific perturbation, complemented by protein structure modeling in silico. We reproduced NADSYN1-dependent CNDD in mice and assessed various maternal NAD precursor supplementation strategies to prevent adverse pregnancy outcomes. While for Nadsyn1+/- mothers, any B3 vitamer was suitable to raise NAD, preventing embryo loss and malformation, Nadsyn1-/- mothers required supplementation with amidated NAD precursors (nicotinamide or nicotinamide mononucleotide) bypassing their metabolic block. The circulatory NAD metabolome in mice and humans before and after NAD precursor supplementation revealed a consistent metabolic signature with utility for patient identification. Our data collectively improve clinical diagnostics of NADSYN1-dependent CNDD, provide guidance for the therapeutic prevention of CNDD, and suggest an ongoing need to maintain NAD levels via amidated NAD precursor supplementation after birth.

Efficacy and safety of factor Xa inhibitors in low body weight patients

STUDY OBJECTIVE

The purpose of this study is to provide evidence for the safety and efficacy of factor Xa inhibitors in patients with a weight ≤60 kg or BMI < 18.5 kg/m2 .

DESIGN

Multicenter, retrospective, cohort study.

SETTING

Twenty-two Ascension Health hospitals.

PATIENTS

Low-body-weight adult patients (weight ≤ 60 kg or BMI < 18.5 kg/m2 ) receiving treatment for atrial fibrillation or venous thromboembolism.

INTERVENTION

Factor Xa inhibitors (apixaban or rivaroxaban) or warfarin.

MEASUREMENTS AND MAIN RESULTS

This study included 2538 patients between the factor Xa inhibitors (n = 1695) and warfarin (n = 843) groups with a mean weight of 53.5 ± 5.5 kg and BMI of 20.7 ± 3.1 kg/m2 . No significant difference in time to major bleeding was noted after controlling for potential confounders (HR 1.03, 95% CI 0.70-1.53, p = 0.87); similar results were seen following propensity score matching. Thromboembolism (5.3% vs. 6.2%, p = 0.38), composite major + clinically relevant nonmajor bleeding (9.8% vs. 11.5%, p = 0.18), and all-cause mortality (10.7% vs. 12.8%, p = 0.12) were similar between patients receiving factor Xa inhibitors versus warfarin.

CONCLUSION

No differences in safety or effectiveness were noted between factor Xa inhibitors versus warfarin. These findings provide encouraging evidence to support the use of factor Xa inhibitors in low-body-weight patients.

Best Practice for Identification of Classical 21-Hydroxylase Deficiency Should Include 21 Deoxycortisol Analysis with Appropriate Isomeric Steroid Separation

There are mixed reports on the inclusion and use of 21 deoxycortisol (21DF) as the primary decision marker for classical 21-hydroxylase deficiency. We hypothesize that this may be due to insufficient recognition of the presence and chromatographic separation of isomeric steroids. The aim of this study was to determine the comparative utility of 21DF for screening and diagnosis of CAH due to classical 21-hydroxylase deficiency using a second-tier LC-MS/MS method that included the separation of isomeric steroids to 17OHP and 21DF. For each baby sample, one 3.2 mm dried blood spot was eluted in a methanolic solution containing isotopically matched internal standards. Data were interrogated by univariate and receiver operator characteristic analysis. Steroid profile results were generated for 924 non-CAH baby samples (median gestational age 37 weeks, range 22 to 43 weeks) and 17 babies with 21-hydroxylase deficiency. The ROC curves demonstrated 21DF to have the best sensitivity and specificity for the diagnosis of classical 21-hydroxylase deficiency with an AUC = 1.0. The heatmap showed the very strong correlation (r = 0.83) between 17OHP and 21DF. Our data support 21DF as a robust marker for CAH due to 21-hydroxylase deficiency. We recommend that 21DF be incorporated into routine newborn screening panels as part of the second-tier LC-MS/MS method, follow-up plasma steroid panels, and external quality assurance material.

Interstitial lung disease and pancreatic exocrine insufficiency in CADDS: Phenotypic expansion and literature review

Contiguous ABCD1/ DXS1357E deletion syndrome (CADDS) is a rare deletion syndrome involving two contiguous genes on Xq28, ABCD1 and BCAP31 (formerly known as DXS1357E). Only nine individuals with this diagnosis have been reported in the medical literature to date. Intragenic loss-of-function variants in BCAP31 cause the deafness, dystonia, and cerebral hypomyelination syndrome (DDCH). Isolated pathogenic intragenic variants in ABCD1 are associated with the most common peroxisomal disorder, X-linked adrenoleukodystrophy (X-ALD), a single transporter deficiency, which in its more severe cerebral form is characterised by childhood-onset neurodegeneration and high levels of very-long-chain fatty acids (VLCFA). While increased VLCFA levels also feature in CADDS, the few patients described to date all presented as neonates with a severe phenotype. Here we report a tenth individual with CADDS, a male infant with dysmorphic facial features who was diagnosed through ultra-rapid whole genome sequencing (WGS) in the setting of persistent cholestatic liver disease, sensorineural hearing loss, hypotonia and growth failure and developmental delay. Biochemical studies showed elevated VLCFA and mildly reduced plasmalogens. He died at 7 months having developed pancreatic exocrine deficiency and interstitial lung disease, two features we propose to be possible extensions to the CADDS phenotype. We also review the genetic, phenotypic, and biochemical features in previously reported individuals with CADDS.

MOGS-CDG: Quantitative analysis of the diagnostic Glc3 Man tetrasaccharide and clinical spectrum of six new cases

Congenital disorders of glycosylation (CDG) are a clinically and biochemically heterogeneous subgroup of inherited metabolic disorders. Most CDG with abnormal N-glycosylation can be detected by transferrin screening, however, MOGS-CDG escapes this routine screening. Combined with the clinical heterogeneity of reported cases, diagnosing MOGS-CDG can be challenging. Here, we clinically characterize ten MOGS-CDG cases including six previously unreported individuals, showing a phenotype characterized by dysmorphic features, global developmental delay, muscular hypotonia, and seizures in all patients and in a minority vision problems and hypogammaglobulinemia. Glycomics confirmed accumulation of a Glc₃ Man₇ GlcNAc₂ glycan in plasma. For quantification of the diagnostic Glcα1-3Glcα1-3Glcα1-2Man tetrasaccharide in urine, we developed and validated a liquid chromatography-mass spectrometry method of 2-aminobenzoic acid (2AA) labeled urinary glycans. As an internal standard, isotopically labeled ¹³ C₆ -2AA Glc₃ Man was used, while labeling efficiency was controlled by use of ¹² C₆ -2AA and ¹³ C₆ -2AA labeled laminaritetraose. Recovery, linearity, intra- and interassay coefficients of variability of these labeled compounds were determined. Furthermore, Glc₃ Man was specifically identified by retention time matching against authentic MOGS-CDG urine and compared with Pompe urine. Glc₃ Man was increased in all six analyzed cases, ranging from 34.1 to 618.0 μmol/mmol creatinine (reference <5 μmol). In short, MOGS-CDG has a broad manifestation of symptoms but can be diagnosed with the use of a quantitative method for analysis of urinary Glc₃ Man excretion.

Loss of mitochondrial fatty acid β-oxidation protein short-chain Enoyl-CoA hydratase disrupts oxidative phosphorylation protein complex stability and function

Short-chain enoyl-CoA hydratase 1 (ECHS1) is involved in the second step of mitochondrial fatty acid β-oxidation (FAO), catalysing the hydration of short-chain enoyl-CoA esters to short-chain 3-hyroxyl-CoA esters. Genetic deficiency in ECHS1 (ECHS1D) is associated with a specific subset of Leigh Syndrome, a disease typically caused by defects in oxidative phosphorylation (OXPHOS). Here, we examined the molecular pathogenesis of ECHS1D using a CRISPR/Cas9 edited human cell 'knockout' model and fibroblasts from ECHS1D patients. Transcriptome analysis of ECHS1 'knockout' cells showed reductions in key mitochondrial pathways, including the tricarboxylic acid cycle, receptor-mediated mitophagy and nucleotide biosynthesis. Subsequent proteomic analyses confirmed these reductions and revealed additional defects in mitochondrial oxidoreductase activity and fatty acid β-oxidation. Functional analysis of ECHS1 'knockout' cells showed reduced mitochondrial oxygen consumption rates when metabolising glucose or OXPHOS complex I-linked substrates, as well as decreased complex I and complex IV enzyme activities. ECHS1 'knockout' cells also exhibited decreased OXPHOS protein complex steady-state levels (complex I, complex III₂ , complex IV, complex V and supercomplexes CIII₂ /CIV and CI/CIII₂ /CIV), which were associated with a defect in complex I assembly. Patient fibroblasts exhibit varied reduction of mature OXPHOS complex steady-state levels, with defects detected in CIII₂ , CIV, CV and the CI/CIII₂ /CIV supercomplex. Overall, these findings highlight the contribution of defective OXPHOS function, in particular complex I deficiency, to the molecular pathogenesis of ECHS1D.

The relationship between beta-ureidopropionase deficiency due to UPB1 variants and human phenotypes is uncertain

BACKGROUND

Beta-ureidopropionase deficiency, caused by variants in UPB1, has been reported in association with various neurodevelopmental phenotypes including intellectual disability, seizures and autism.

AIM

We aimed to reassess the relationship between variants in UPB1 and a clinical phenotype.

METHODS

Literature review, calculation of carrier frequencies from population databases, long-term follow-up of a previously published case and reporting of additional cases.

RESULTS

Fifty-three published cases were identified, and two additional cases are reported here. Of these, 14 were asymptomatic and four had transient neurological features; clinical features in the remainder were variable and included non-neurological presentations. Several of the variants previously reported as pathogenic are present in population databases at frequencies higher than expected for a rare condition. In particular, the variant most frequently reported as pathogenic, p.Arg326Gln, is very common among East Asians, with a carrier frequency of 1 in 19 and 1 in 907 being homozygous for the variant in gnomAD v2.1.1.

CONCLUSION

Pending the availability of further evidence, UPB1 should be considered a 'gene of uncertain clinical significance'. Caution should be used in ascribing clinical significance to biochemical features of beta-ureidopropionase deficiency and/or UPB1 variants in patients with neurodevelopmental phenotypes. UPB1 is not currently suitable for inclusion in gene panels for reproductive genetic carrier screening.

SYNOPSIS

The relationship between beta-ureidopropionase deficiency due to UPB1 variants and clinical phenotypes is uncertain.

Free urinary sialic acid levels may be elevated in patients with pneumococcal sepsis

OBJECTIVES

Urine free sialic acid (UFSA) is an important diagnostic biomarker for sialuria (GNE variants) and infantile sialic acid storage disease/Salla disease (SLC17A5 variants). Traditionally, UFSA has been measured using specific single-plex methodology in relatively small cohorts of patients with clinical symptoms suggestive of these disorders. The use of multiplex tandem mass spectrometry urine screening (UMSMS) has meant that UFSA can be measured semi-quantitatively in a much larger cohort of patients being investigated for suspected metabolic disorders. We hypothesised that the neuraminidase of Streptococcus pneumoniae may release free sialic acid from endogenous sialylated glycoconjugates and result in increased UFSA levels.

METHODS

We conducted a retrospective review of clinical records of patients who were identified as having S. pneumoniae infection and who also had UMSMS at the time of their acute infection.

RESULTS

We identified three cases of increased UFSA detected by UMSMS screening that were secondary to S. pneumoniae sepsis. Additional testing ruled out genetic causes of increased UFSA in the first patient. All three patients had overwhelming sepsis with multiorgan dysfunction which was fatal. Glycosylation abnormalities consistent with the removal of sialic acid were demonstrated in serum transferrin patterns in one patient.

CONCLUSIONS

We have demonstrated in a retrospective cohort that elevation of UFSA levels have been observed in cases of S. pneumoniae sepsis. This expands our knowledge of UFSA as a biomarker in human disease. This research demonstrates that infection with organisms with neuraminidase activity should be considered in patients with unexplained increases in UFSA.

Evaluation of prognostic risk models for postoperative pulmonary complications in adult patients undergoing major abdominal surgery: a systematic review and international external validation cohort study

BACKGROUND

Stratifying risk of postoperative pulmonary complications after major abdominal surgery allows clinicians to modify risk through targeted interventions and enhanced monitoring. In this study, we aimed to identify and validate prognostic models against a new consensus definition of postoperative pulmonary complications.

METHODS

We did a systematic review and international external validation cohort study. The systematic review was done in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. We searched MEDLINE and Embase on March 1, 2020, for articles published in English that reported on risk prediction models for postoperative pulmonary complications following abdominal surgery. External validation of existing models was done within a prospective international cohort study of adult patients (≥18 years) undergoing major abdominal surgery. Data were collected between Jan 1, 2019, and April 30, 2019, in the UK, Ireland, and Australia. Discriminative ability and prognostic accuracy summary statistics were compared between models for the 30-day postoperative pulmonary complication rate as defined by the Standardised Endpoints in Perioperative Medicine Core Outcome Measures in Perioperative and Anaesthetic Care (StEP-COMPAC). Model performance was compared using the area under the receiver operating characteristic curve (AUROCC).

FINDINGS

In total, we identified 2903 records from our literature search; of which, 2514 (86·6%) unique records were screened, 121 (4·8%) of 2514 full texts were assessed for eligibility, and 29 unique prognostic models were identified. Nine (31·0%) of 29 models had score development reported only, 19 (65·5%) had undergone internal validation, and only four (13·8%) had been externally validated. Data to validate six eligible models were collected in the international external validation cohort study. Data from 11 591 patients were available, with an overall postoperative pulmonary complication rate of 7·8% (n=903). None of the six models showed good discrimination (defined as AUROCC ≥0·70) for identifying postoperative pulmonary complications, with the Assess Respiratory Risk in Surgical Patients in Catalonia score showing the best discrimination (AUROCC 0·700 [95% CI 0·683-0·717]).

INTERPRETATION

In the pre-COVID-19 pandemic data, variability in the risk of pulmonary complications (StEP-COMPAC definition) following major abdominal surgery was poorly described by existing prognostication tools. To improve surgical safety during the COVID-19 pandemic recovery and beyond, novel risk stratification tools are required.

FUNDING

British Journal of Surgery Society.

Ethylmalonic encephalopathy masquerading as meningococcemia

Ethylmalonic encephalopathy (MIM #602473) is a rare autosomal recessive metabolic condition caused by biallelic variants in ETHE1 (MIM #608451), characterized by global developmental delay, infantile hypotonia, seizures, and microvascular damage. The microvascular changes result in a pattern of relapsing spontaneous diffuse petechiae and purpura, positional acrocyanosis, and pedal edema, hemorrhagic suffusions of mucous membranes, and chronic diarrhea. Here, we describe an instructive case in which ethylmalonic encephalopathy masqueraded as meningococcal septicemia and shock. Ultrarapid whole-genome testing (time to result 60 h) and prompt biochemical analysis facilitated accurate diagnosis and counseling with rapid implementation of precision treatment for the metabolic crisis related to this condition. This case provides a timely reminder to consider rare genetic diagnoses when atypical features of more common conditions are present, with an early referral to ensure prompt biochemical and genomic diagnosis.

Feasibility of Screening for Chromosome 15 Imprinting Disorders in 16 579 Newborns by Using a Novel Genomic Workflow

IMPORTANCE

Newborn screening for Angelman syndrome (AS), Prader-Willi syndrome (PWS), and chromosome 15 duplication syndrome (Dup15q) may lead to benefit from early diagnosis and treatment.

OBJECTIVE

To examine the feasibility of newborn screening for these chromosome 15 imprinting disorders at population scale.

DESIGN, SETTING, AND PARTICIPANTS

In this diagnostic study, the validation data set for the first-tier SNRPN test, called methylation-specific quantitative melt analysis (MS-QMA), included 109 PWS, 48 AS, 9 Dup15q, and 1190 population control newborn blood spots (NBS) and peripheral tissue samples from participants recruited from January 2000 to December 2016. The test data set included NBS samples from 16 579 infants born in 2011. Infants with an NBS identified as positive for PWS, AS, or Dup15q by the first-tier test were referred for droplet digital polymerase chain reaction, real-time polymerase chain reaction, and low-coverage whole-genome sequencing for confirmatory testing. Data analyses were conducted between February 12, 2015, and August 15, 2020.

RESULTS

In the validation data set, the median age for the 77 patients with PWS was 3.00 years (IQR, 0.01-44.50 years); for the 46 patients with AS, 2.76 years (IQR, 0.028 to 49.00 years); and for the 9 patients with Dup15q, 4.00 years (IQR, 1.00 to 28.00 years). Thirty-eight patients (51.4%) in the PWS group, 20 patients (45.5%) in the AS group, and 6 patients (66.7%) in the Dup15q group who had sex reported were male. The validation data set showed MS-QMA sensitivity of 99.0% for PWS, 93.8% for AS, and 77.8% for Dup15q; specificity of 100% for PWS, AS, and Dup15q; positive predictive and negative predictive values of 100% for PWS and AS; and a positive predictive value of 87.5% and negative predictive value of 100% for Dup15q. In the test data set of NBS samples from 16 579 infants, 92 had a positive test result using a methylation ratio cut-off of 3 standard deviations from the mean. Of these patients, 2 were confirmed to have PWS; 2, AS; and 1, maternal Dup15q. With the use of more conservative PWS- and AS-specific thresholds for positive calls from the validation data set, 9 positive NBS results were identified by MS-QMA in this cohort. The 2 PWS and 2 AS calls were confirmed by second-tier testing, but the 1 Dup15q case was not confirmed. Together, these results provided prevalence estimates of 1 in 8290 for both AS and PWS and 1 in 16 579 for maternal Dup15q, with positive predictive values for first-tier testing at 67.0% for AS, 33.0% for PWS, and 44.0% for combined detection of chromosome 15 imprinting disorders for the validation data set.

CONCLUSIONS AND RELEVANCE

The findings of this diagnostic study suggest that it is feasible to screen for all chromosome 15 imprinting disorders using SNRPN methylation analysis, with 5 individuals identified with these disorders out of 16 579 infants screened.

Active site variants in STT3A cause a dominant type I congenital disorder of glycosylation with neuromusculoskeletal findings

Congenital disorders of glycosylation (CDGs) form a group of rare diseases characterized by hypoglycosylation. We here report the identification of 16 individuals from nine families who have either inherited or de novo heterozygous missense variants in STT3A, leading to an autosomal-dominant CDG. STT3A encodes the catalytic subunit of the STT3A-containing oligosaccharyltransferase (OST) complex, essential for protein N-glycosylation. Affected individuals presented with variable skeletal anomalies, short stature, macrocephaly, and dysmorphic features; half had intellectual disability. Additional features included increased muscle tone and muscle cramps. Modeling of the variants in the 3D structure of the OST complex indicated that all variants are located in the catalytic site of STT3A, suggesting a direct mechanistic link to the transfer of oligosaccharides onto nascent glycoproteins. Indeed, expression of STT3A at mRNA and steady-state protein level in fibroblasts was normal, while glycosylation was abnormal. In S. cerevisiae, expression of STT3 containing variants homologous to those in affected individuals induced defective glycosylation of carboxypeptidase Y in a wild-type yeast strain and expression of the same mutants in the STT3 hypomorphic stt3-7 yeast strain worsened the already observed glycosylation defect. These data support a dominant pathomechanism underlying the glycosylation defect. Recessive mutations in STT3A have previously been described to lead to a CDG. We present here a dominant form of STT3A-CDG that, because of the presence of abnormal transferrin glycoforms, is unusual among dominant type I CDGs.

Early-onset vitamin B6-dependent epilepsy due to pathogenic PLPBP variants in a premature infant: A case report and review of the literature

Vitamin B6-dependent epilepsies are a heterogeneous group of disorders characterized by decreased availability of the active cofactor pyridoxal-5'-phosphate (PLP). While pathogenic variants in ALDH7A1 or PNPO genes account for most cases of these disorders, biallelic pathogenic variants in PLPBP have been shown to cause a form of early onset vitamin B6-dependent epilepsy (EPVB6D). PLPBP is thought to play a role in the homeostatic regulation of vitamin B6, by supplying PLP to apoenzymes while limiting side-reaction toxicity related to excess unbound PLP. Neonatal-onset intractable seizures that respond to pyridoxine and/or PLP are a predominant feature of EPVB6D in humans. Unlike other causes of vitamin B6-dependent epilepsies; however, a specific biomarker for this disorder has yet to be identified. Here we present data from a premature infant found to have pathogenic variants in PLPBP and propose that prematurity may provide an additional clue for early consideration of this diagnosis. We discuss these findings in context of previously published genotypic, phenotypic, and metabolic data from similarly affected patients.

ECHS1 disease in two unrelated families of Samoan descent: Common variant - rare disorder

Mutations in the short-chain enoyl-CoA hydratase (SCEH) gene, ECHS1, cause a rare autosomal recessive disorder of valine catabolism. Patients usually present with developmental delay, regression, dystonia, feeding difficulties, and abnormal MRI with bilateral basal ganglia involvement. We present clinical, biochemical, molecular, and functional data for four affected patients from two unrelated families of Samoan descent with identical novel compound heterozygous mutations. Family 1 has three affected boys while Family 2 has an affected daughter, all with clinical and MRI findings of Leigh syndrome and intermittent episodes of acidosis and ketosis. WES identified a single heterozygous variant in ECHS1 at position c.832G > A (p.Ala278Thr). However, western blot revealed significantly reduced ECHS1 protein for all affected family members. Decreased SCEH activity in fibroblasts and a mild increase in marker metabolites in urine further supported ECHS1 as the underlying gene defect. Additional investigations at the DNA (aCGH, WGS) and RNA (qPCR, RT-PCR, RNA-Seq, RNA-Array) level identified a silent, common variant at position c.489G > A (p.Pro163=) as the second mutation. This substitution, present at high frequency in the Samoan population, is associated with decreased levels of normally spliced mRNA. To our understanding, this is the first report of a novel, hypomorphic allele c.489G > A (p.Pro163=), associated with SCEH deficiency.

Successful treatment of lathosterolosis: A rare defect in cholesterol biosynthesis-A case report and review of literature

Lathosterolosis is a rare autosomal recessive disorder of cholesterol biosynthesis. It is caused by defects in the SC5D (sterol C5-desaturase) gene which encodes for the 3-beta-hydroxysteroid-delta-5-desaturase (also called sterol-C5-desaturase or lathosterol dehydrogenase). Only six cases have been described in the literature, but it is possible that a number of patients with milder forms of the condition might have been missed. Lathosterolosis manifests as microcephaly, bilateral cataracts, dysmorphism, limb anomalies, and developmental delay/intellectual disability. Liver involvement is variable and can range from normal liver function tests to portal fibrosis and cirrhosis. Diagnosis is made by demonstration of specific mutations in the SC5D gene and by plasma sterol analysis to confirm elevated lathosterol levels. In this report, we describe a girl with transaminitis in association with developmental delay/intellectual disability, facial dysmorphism, limb anomalies, and bilateral cataracts. Fibroscan showed severe liver fibrosis. Plasma sterol analysis and exome sequencing confirmed the diagnosis of lathosterolosis. Simvastatin treatment resulted in lowering of plasma lathosterol levels, improvement in transaminitis, and liver fibrosis grade, suggesting that children with this condition should be actively treated in order to prevent progression of liver disease.

Dig deeper when it does not make sense: Juvenile xanthomas due to sitosterolemia

Sitosterolemia is an extremely rare autosomal recessive disease caused by mutations in either ABCG5 or ABCG8, which encode for a sterol efflux transporter (sterolin) that pumps sterols out into the intestinal lumen or into bile. This leads to progressive accumulation of plant sterols in blood and tissues. Clinical presentation is variable and may include xanthoma, arthritis, thyroid dysfunction, premature atherosclerotic disease, splenomegaly, and hematologic manifestations. We report a child presented with multiple xanthomas at age 5.5 years, located on the elbow, knee, and toe. Juvenile xanthogranuloma was considered based on histopathologic findings. At 8 years of age, a lipid profile showed markedly elevated total cholesterol (9.4 mmol/L) and low-density lipoprotein cholesterol (LDL-C, 7.4 mmol/L). Simvastatin therapy was initiated, however, the lipid profile was persistently abnormal. At age 8.5 years, genetic testing identified two novel variants: (NM_022437.3[ABCG8]:c.1444del;p.Leu482Trpfs*40) and (NM_022437.3[ABCG8]:c.1640T>C;p.Leu547Pro) in the ABCG8 gene. Plasma sitosterol was subsequently found to be very high, confirming the diagnosis. She was started on a low plant sterol and cholesterol diet for 6 weeks with insignificant response and therefore ezetimibe (10 mg daily) was added. This resulted in significant reduction of cholesterol, LDL, sitosterol levels, and no further increase in the size of the xanthomas. This case emphasizes the diagnostic odyssey, the benefits of genomic testing and importance of a correct diagnosis in order to initiate appropriate therapy. It also illustrates the importance of considering rare conditions, such as sitosterolemia, as a differential diagnosis in patients with hypercholesterolemia and increased LDL-C.

Age, Sex, and Depot-Specific Differences in Adipose-Tissue Estrogen Receptors in Individuals with Obesity

OBJECTIVE

The aim of this study was to examine the effects of sex and menopausal status on depot-specific estrogen signaling in white adipose tissue (AT) in age-matched men and women with morbid obesity.

METHODS

A total of 28 premenopausal women, 16 postmenopausal women, and 27 age-matched men undergoing bariatric surgery were compared for omental (OM) AT (OMAT) and abdominal subcutaneous (SQ) AT (SQAT) genes and proteins.

RESULTS

With the exception of fasting nonesterified fatty acids being higher in women (P < 0.01), no differences were found in other indicators of glucose and lipid metabolism. In OMAT, estrogen receptor (ER) beta (ERβ) levels were higher in older women than in younger women and older men (sex-age interaction, P < 0.01), and aromatase expression was higher in older men than in older women (P < 0.05). In SQAT, women had lower expression of ERβ than men (P < 0.05). Protein content of ER alpha and ERβ was highly correlated with the mitochondrial protein uncoupling protein 1 across sexes and ages (P < 0.001). Age increased SQ inflammatory gene expression in both sexes.

CONCLUSIONS

In morbid obesity, sex and age affect AT ERs, lipid metabolism, mitochondrial uncoupling protein 1, and inflammatory expression in an AT depot-dependent manner. The SQAT immunometabolic profile is heavily influenced by age and menopause status, more so than OMAT.

Perioperative intravenous contrast administration and the incidence of acute kidney injury after major gastrointestinal surgery: prospective, multicentre cohort study

BACKGROUND

This study aimed to determine the impact of preoperative exposure to intravenous contrast for CT and the risk of developing postoperative acute kidney injury (AKI) in patients undergoing major gastrointestinal surgery.

METHODS

This prospective, multicentre cohort study included adults undergoing gastrointestinal resection, stoma reversal or liver resection. Both elective and emergency procedures were included. Preoperative exposure to intravenous contrast was defined as exposure to contrast administered for the purposes of CT up to 7 days before surgery. The primary endpoint was the rate of AKI within 7 days. Propensity score-matched models were adjusted for patient, disease and operative variables. In a sensitivity analysis, a propensity score-matched model explored the association between preoperative exposure to contrast and AKI in the first 48 h after surgery.

RESULTS

A total of 5378 patients were included across 173 centres. Overall, 1249 patients (23·2 per cent) received intravenous contrast. The overall rate of AKI within 7 days of surgery was 13·4 per cent (718 of 5378). In the propensity score-matched model, preoperative exposure to contrast was not associated with AKI within 7 days (odds ratio (OR) 0·95, 95 per cent c.i. 0·73 to 1·21; P = 0·669). The sensitivity analysis showed no association between preoperative contrast administration and AKI within 48 h after operation (OR 1·09, 0·84 to 1·41; P = 0·498).

CONCLUSION

There was no association between preoperative intravenous contrast administered for CT up to 7 days before surgery and postoperative AKI. Risk of contrast-induced nephropathy should not be used as a reason to avoid contrast-enhanced CT.

Rare presentation of De Garengeot hernia in a 77-year-old woman

A 77-year-old woman presented with a rare surgical phenomenon known as De Garengeot hernia. This unique presentation occurs due to the presence of a vermiform appendix in a femoral hernia sac. The patient presented with right-sided groin pain and a partially reducible hernia; she was otherwise haemodynamically stable and denied fevers, nausea and vomiting. The diagnosis was confirmed with CT which demonstrated a right-sided femoral hernia containing a perforated tip of the appendix. The patient urgently underwent an open appendectomy and open right femoral hernia repair using the modified McEvedy’s incision.

A Systematic Review and Meta-Analysis of Single-Incision Versus Multiport Laparoscopic Complete Mesocolic Excision Colectomy for Colon Cancer

Background. Our aim was to compare the emerging technique of single-incision laparoscopic surgery complete mesocolic excision (SILS CME) colectomy with the standard multiport laparoscopic CME (MPL CME) colectomy. Methods. MEDLINE (PubMed), Scopus, EMBASE, Ovid, and the Cochrane library were searched. Studies comparing the SILS CME with MPL CME in adults with colon adenocarcinoma were included. The Jadad and Newcastle Ottawa Scales were used to critically appraise the studies. The presence of statistical heterogeneity or publication bias was examined. Results. Seven studies (3 randomized) with a total number of 1344 patients were included (546 SILS CME and 798 MPL CME). No difference was found in anastomotic leakage (odds ratio [OR] = 0.79 [0.31 to 2.03]; P = .63), number of lymph nodes (weighted mean difference [WMD] = 0.85 [-0.97 to 2.66]; P = .36), hospital stay (WMD = 0.01 [-0.19 to 0.20]; P = .96), overall survival (hazard ratio [HR] = 1.19 [0.29 to 4.80]; P = .81), and disease-free survival (HR = 1.30 [0.30 to 5.61]; P = .72). Skin incision was shorter in SILS CME group (WMD = -3.02 [-3.25 to -2.80]; P < .00001) but with no difference in pain reported in postoperative day 1 (standardized mean difference [SMD] = -0.21 [-0.50 to 0.09]; P = .17) or day 2 (SMD = 0.16 [-0.52 to 0.84]; P = .64). Conclusions. SILS CME, although technically more demanding, has equivalent short- and long-term outcomes when compared with MPL CME. Potential benefits in cosmesis or postoperative pain need to be further explored by high-quality randomized controlled trials.

Small intestinal bacterial overgrowth in children with intestinal failure on home parenteral nutrition

Background and Aim

Children with intestinal failure (IF) have abnormal intestinal anatomy, secretion, or motility, which impairs homeostatic mechanisms and can lead to small intestinal bacterial overgrowth (SIBO). We sought to describe clinical features at the time of clinically suspected SIBO by experienced clinicians in children with IF on home parenteral nutrition (PN), review specific challenges of diagnostic testing in this population, and describe potential new diagnostic surrogate markers.

Methods

A descriptive single‐center retrospective chart review was performed during all episodes of clinically suspected SIBO over 33 months. Information was recorded on clinical symptoms, and diagnostic tests performed.

Results

Of all patients on home PN, 71% (12/17) had at least one episode of clinically suspected SIBO (mean 1 episode/year, range 1–7); 50% of patients had short bowel syndrome (SBS), and 50% had non‐SBS IF. The average reported symptoms per episode were 1.9 (range 1–5). Children with SBS reported fewer symptoms per episode (1.5) than children with non‐SBS IF (2.3). Diarrhea was the most commonly reported symptom, particularly in children with SBS.

Conclusions

Children with IF on home PN are a high‐risk group for SIBO. Clinical features of SIBO vary depending on the cause of IF and may mimic symptoms of the underlying condition. Diagnostic tests have innate challenges in this group, and a strong index of clinical suspicion is paramount. Further research is recommended into potential new surrogate markers (urinary metabolite screen, gastric aspirate) for this diagnostically challenging population.

Safety assessment of the biotechnologically produced human-identical milk oligosaccharide 3-Fucosyllactose (3-FL)

3-Fucosyllactose (3-FL), a highly abundant complex carbohydrate in human breast milk, functions as a prebiotic promoting early microbial colonization of the gut, increasing pathogen resistance and modulating immune responses. To investigate potential health benefits, 3-FL was produced by fermentation using a genetically modified E. coli K12 strain. The safety assessment of 3-FL included acute oral toxicity, in vitro and in vivo assessment of genetic toxicity, and a subchronic rodent feeding study. 3-FL was not acutely toxic at 5000 mg/kg bw, and there was no evidence of genetic toxicity in the bacterial reverse mutation test and chromosomal aberration assay. There was a repeatable statistically-significant trend in the 4-h S9-activated test conditions in the in vitro micronucleus assay; the confirmatory in vivo mouse micronucleus study was negative at all doses. Dietary subchronic exposure of rats to 3-FL (5% and 10%) did not produce any statistical or biologically-relevant differences in growth, food intake or efficiency, clinical observations, or clinical or anatomic pathology changes at average daily intakes of 5.98 and 7.27 g/kg bw/day for males and females, respectively. The weight of evidence from these studies support the safe use of 3-FL produced using biotechnology as a nutritional ingredient in foods.

Metabolite diagnosis of primary hyperoxaluria type 3

BACKGROUND

Primary hyperoxaluria type 3 (PH3) is a recently described cause of childhood renal calculi. It results from mutations in the HOGA1 gene and most cases have been diagnosed after clinical ascertainment, exclusion of other genetic hyperoxalurias and mutation testing. Metabolite testing has not been widely applied but holds promise for the rapid screening and diagnosis of patients who are not specifically suspected to have PH3.

CASE-DIAGNOSIS/TREATMENT

Two cases presented with renal calculi. Urine metabolite testing by tandem mass spectrometry was performed as part of the routine diagnostic work-up for this condition. Both had significantly increased levels of the PH3 urine marker 4-hydroxyglutamate and related metabolites. The diagnosis of PH3 was confirmed by the finding of bi-allelic damaging HOGA1 mutations.

CONCLUSIONS

Urine screening by tandem mass spectrometry is a rapid, high-throughput test that can detect PH3 cases that may otherwise not be diagnosed.

Squalene Synthase Deficiency: Clinical, Biochemical, and Molecular Characterization of a Defect in Cholesterol Biosynthesis

Mendelian disorders of cholesterol biosynthesis typically result in multi-system clinical phenotypes, underlining the importance of cholesterol in embryogenesis and development. FDFT1 encodes for an evolutionarily conserved enzyme, squalene synthase (SS, farnesyl-pyrophosphate farnesyl-transferase 1), which catalyzes the first committed step in cholesterol biosynthesis. We report three individuals with profound developmental delay, brain abnormalities, 2-3 syndactyly of the toes, and facial dysmorphisms, resembling Smith-Lemli-Opitz syndrome, the most common cholesterol biogenesis defect. The metabolite profile in plasma and urine suggested that their defect was at the level of squalene synthase. Whole-exome sequencing was used to identify recessive disease-causing variants in FDFT1. Functional characterization of one variant demonstrated a partial splicing defect and altered promoter and/or enhancer activity, reflecting essential mechanisms for regulating cholesterol biosynthesis/uptake in steady state.

Genetic, Radiologic, and Clinical Variability in Brown-Vialetto-van Laere Syndrome

Brown-Vialetto-van Laere syndrome is characterized by a progressive sensorimotor neuropathy, optic atrophy, hearing loss, bulbar dysfunction, and respiratory insufficiency. Mutations in SLC52A2 and SLC52A3, encoding riboflavin transporters RFVT2 and RFVT3, respectively, are the genetic basis of this disorder, often referred to as riboflavin transporter deficiency types 2 and 3, respectively. We present cases of both types of riboflavin transporter deficiency, highlighting the distinguishing clinical features of a rapidly progressive motor or sensorimotor axonal neuropathy, optic atrophy, sensorineural hearing loss, and bulbar dysfunction. One child presented with isolated central apnea and hypoventilation, not previously described in genetically confirmed Brown-Vialetto-van Laere, later complicated by diaphragmatic paralysis secondary to phrenic nerve palsy. Magnetic resonance imaging showed T2 hyperintensity in the dorsal spinal cord in 2 children, as well as previously unreported cervical nerve root enlargement and cauda equina ventral nerve root enhancement in 1 child. Novel homozygous mutations were identified in each gene-a NM_024531.4(SLC52A2):c.505C > T, NP_078807.1(SLC52A2):p.(Arg169Cys) variant in SLC52A2 and NM_033409.3(SLC52A3):c.1316G > A, NP_212134.3(SLC52A3):p.(Gly439Asp) variant in SLC52A3. Both treated children showed improvement on high-dose riboflavin supplementation, highlighting the importance of early recognition of this treatable clinical entity.

Development of a low-maintenance measurement approach to continuously estimate methane emissions: A case study

The chemical breakdown of organic matter in landfills represents a significant source of methane gas (CH₄). Current estimates suggest that landfills are responsible for between 3% and 19% of global anthropogenic emissions. The net CH₄ emissions resulting from biogeochemical processes and their modulation by microbes in landfills are poorly constrained by imprecise knowledge of environmental constraints. The uncertainty in absolute CH₄ emissions from landfills is therefore considerable. This study investigates a new method to estimate the temporal variability of CH₄ emissions using meteorological and CH₄ concentration measurements downwind of a landfill site in Suffolk, UK from July to September 2014, taking advantage of the statistics that such a measurement approach offers versus shorter-term, but more complex and instantaneously accurate, flux snapshots. Methane emissions were calculated from CH₄ concentrations measured 700m from the perimeter of the landfill with observed concentrations ranging from background to 46.4ppm. Using an atmospheric dispersion model, we estimate a mean emission flux of 709μgm^-2s^-1 over this period, with a maximum value of 6.21mgm^-2s^-1, reflecting the wide natural variability in biogeochemical and other environmental controls on net site emission. The emissions calculated suggest that meteorological conditions have an influence on the magnitude of CH₄ emissions. We also investigate the factors responsible for the large variability observed in the estimated CH₄ emissions, and suggest that the largest component arises from uncertainty in the spatial distribution of CH₄ emissions within the landfill area. The results determined using the low-maintenance approach discussed in this paper suggest that a network of cheaper, less precise CH₄ sensors could be used to measure a continuous CH₄ emission time series from a landfill site, something that is not practical using far-field approaches such as tracer release methods. Even though there are limitations to the approach described here, this easy, low-maintenance, low-cost method could be used by landfill operators to estimate time-averaged CH₄ emissions and their impact downwind by simultaneously monitoring plume advection and CH₄ concentrations.

Newborn screening for severe combined immunodeficiency: Evaluation of a commercial T-cell receptor excision circle-based method in Victorian dried blood spots

AIM

Severe combined immunodeficiency (SCID) is the most severe form of primary immunodeficiency and is fatal in infancy if untreated. As early diagnosis is associated with improved outcomes, SCID is an ideal condition to consider for inclusion in a newborn screening (NBS) programme in Australia. In this feasibility study, we evaluated the EnLite Neonatal TREC kit for detection of T-cell receptor excision circles (TRECs) from NBS dried blood spots for the identification of known SCID patients in Victoria.

METHODS

TREC copies/μL were measured retrospectively in 14 children diagnosed with SCID or complete DiGeorge syndrome (CDGS) from 2005 to 2015 at the Royal Children's Hospital, Melbourne. In addition, TREC copies/μL were measured for 501 prospective de-identified NBS cards.

RESULTS

Of 14 known SCID or CDGS samples, 11 were correctly identified as presumptive positive samples with low or undetectable TREC on duplicate testing. The remaining three samples also had low or undetectable TREC on duplicate testing but were considered invalid due to insufficient β-actin DNA amplification. Of the 501 prospective NBS samples, none were identified as presumptive positive samples on duplicate testing.

CONCLUSIONS

The EnLite Neonatal TREC kit correctly identified known SCID or CDGS patients as presumptive positive samples, and initial cut-offs for TREC and β-actin in the Victorian NBS population were determined. A larger pilot study is required to confirm these proposed cut-offs and to evaluate the cost and implementation of this screening programme in Victoria, Australia. Overall, this study provides preliminary data to support the introduction of this assay to the NBS programme in Victoria.

Mild orotic aciduria in UMPS heterozygotes: a metabolic finding without clinical consequences

BACKGROUND

Elevated urinary excretion of orotic acid is associated with treatable disorders of the urea cycle and pyrimidine metabolism. Establishing the correct and timely diagnosis in a patient with orotic aciduria is key to effective treatment. Uridine monophosphate synthase is involved in de novo pyrimidine synthesis. Uridine monophosphate synthase deficiency (or hereditary orotic aciduria), due to biallelic mutations in UMPS, is a rare condition presenting with megaloblastic anemia in the first months of life. If not treated with the pyrimidine precursor uridine, neutropenia, failure to thrive, growth retardation, developmental delay, and intellectual disability may ensue.

METHODS AND RESULTS

We identified mild and isolated orotic aciduria in 11 unrelated individuals with diverse clinical signs and symptoms, the most common denominator being intellectual disability/developmental delay. Of note, none had blood count abnormalities, relevant hyperammonemia or altered plasma amino acid profile. All individuals were found to have heterozygous alterations in UMPS. Four of these variants were predicted to be null alleles with complete loss of function. The remaining variants were missense changes and predicted to be damaging to the normal encoded protein. Interestingly, family screening revealed heterozygous UMPS variants in combination with mild orotic aciduria in 19 clinically asymptomatic family members.

CONCLUSIONS

We therefore conclude that heterozygous UMPS-mutations can lead to mild and isolated orotic aciduria without clinical consequence. Partial UMPS-deficiency should be included in the differential diagnosis of mild orotic aciduria. The discovery of heterozygotes manifesting clinical symptoms such as hypotonia and developmental delay are likely due to ascertainment bias.

Unravelling the metabolic impact of SBS-associated microbial dysbiosis: Insights from the piglet short bowel syndrome model

Liver disease is a major source of morbidity and mortality in children with short bowel syndrome (SBS). SBS-associated microbial dysbiosis has recently been implicated in the development of SBS-associated liver disease (SBS-ALD), however the pathological implications of this association have not been explored. In this study high-throughput sequencing of colonic content from the well-validated piglet SBS-ALD model was examined to determine alterations in microbial communities, and concurrent metabolic alterations identified in urine samples via targeted mass spectrometry approaches (GC-MS, LC-MS, FIA-MS) further uncovered impacts of microbial disturbance on metabolic outcomes in SBS-ALD. Multi-variate analyses were performed to elucidate contributing SBS-ALD microbe and metabolite panels and to identify microbe-metabolite interactions. A unique SBS-ALD microbe panel was clearest at the genus level, with discriminating bacteria predominantly from the Firmicutes and Bacteroidetes phyla. The SBS-ALD metabolome included important alterations in the microbial metabolism of amino acids and the mitochondrial metabolism of branched chain amino acids. Correlation analysis defined microbe-metabolite clustering patterns unique to SBS-ALD and identified a metabolite panel that correlates with dysbiosis of the gut microbiome in SBS.

Constraints on oceanic methane emissions west of Svalbard from atmospheric in situ measurements and Lagrangian transport modeling

Methane stored in seabed reservoirs such as methane hydrates can reach the atmosphere in the form of bubbles or dissolved in water. Hydrates could destabilize with rising temperature further increasing greenhouse gas emissions in a warming climate. To assess the impact of oceanic emissions from the area west of Svalbard, where methane hydrates are abundant, we used measurements collected with a research aircraft (Facility for Airborne Atmospheric Measurements) and a ship (Helmer Hansen) during the Summer 2014 and for Zeppelin Observatory for the full year. We present a model-supported analysis of the atmospheric CH₄ mixing ratios measured by the different platforms. To address uncertainty about where CH₄ emissions actually occur, we explored three scenarios: areas with known seeps, a hydrate stability model, and an ocean depth criterion. We then used a budget analysis and a Lagrangian particle dispersion model to compare measurements taken upwind and downwind of the potential CH₄ emission areas. We found small differences between the CH₄ mixing ratios measured upwind and downwind of the potential emission areas during the campaign. By taking into account measurement and sampling uncertainties and by determining the sensitivity of the measured mixing ratios to potential oceanic emissions, we provide upper limits for the CH₄ fluxes. The CH₄ flux during the campaign was small, with an upper limit of 2.5 nmol m^-2 s^-1 in the stability model scenario. The Zeppelin Observatory data for 2014 suggest CH₄ fluxes from the Svalbard continental platform below 0.2 Tg yr^-1. All estimates are in the lower range of values previously reported.

Clinical, biochemical and metabolic characterisation of a mild form of human short-chain enoyl-CoA hydratase deficiency: significance of increased N-acetyl-S-(2-carboxypropyl)cysteine excretion

BACKGROUND

Short-chain enoyl-CoA hydratase-ECHS1-catalyses many metabolic pathways, including mitochondrial short-chain fatty acid β-oxidation and branched-chain amino acid catabolic pathways; however, the metabolic products essential for the diagnosis of ECHS1 deficiency have not yet been determined. The objective of this report is to characterise ECHS1 and a mild form of its deficiency biochemically, and to determine the candidate metabolic product that can be efficiently used for neonatal diagnosis.

METHODS

We conducted a detailed clinical, molecular genetics, biochemical and metabolic analysis of sibling patients with ECHS1 deficiency. Moreover, we purified human ECHS1, and determined the substrate specificity of ECHS1 for five substrates via different metabolic pathways.

RESULTS

Human ECHS1 catalyses the hydration of five substrates via different metabolic pathways, with the highest specificity for crotonyl-CoA and the lowest specificity for tiglyl-CoA. The patients had relatively high (∼7%) residual ECHS1 enzyme activity for crotonyl-CoA and methacrylyl-CoA caused by the compound heterozygous mutations (c.176A>G, (p.N59S) and c.413C>T, (p.A138V)) with normal mitochondrial complex I-IV activities. Affected patients excrete large amounts of N-acetyl-S-(2-carboxypropyl)cysteine, a metabolite of methacrylyl-CoA.

CONCLUSIONS

Laboratory data and clinical features demonstrated that the patients have a mild form of ECHS1 deficiency harbouring defective valine catabolic and β-oxidation pathways. N-Acetyl-S-(2-carboxypropyl) cysteine level was markedly high in the urine of the patients, and therefore, N-acetyl-S-(2-carboxypropyl)cysteine was regarded as a candidate metabolite for the diagnosis of ECHS1 deficiency. This metabolite is not part of current routine metabolic screening protocols, and its inclusion, therefore, holds immense potential in accurate diagnosis.

Metabolite studies in HIBCH and ECHS1 defects: Implications for screening

3-Hydroxyisobutyryl-CoA hydrolase deficiency (HIBCHD) is a rare inborn error of the valine catabolic pathway associated with Leigh-like disease. We report a female patient who presented at the age of 5months with hypotonia, developmental delay and cerebral atrophy on MRI. Pyruvate dehydrogenase deficiency was initially suspected and decreased activity was shown in fibroblasts. Urine tandem mass spectrometry screening showed large increases in the cysteine conjugate of methacrylate previously described in HIBCHD. 3-hydroxyisobutyryl-CoA hydrolase activity in fibroblasts was below the limit of detection of the enzymatic assay and two novel HIBCH mutations were identified (c.[129dupA];[1033G>A]). Urine metabolite investigations also showed increases in 3-hydroxyisobutyryl carnitine, 2,3-dihydroxy-2-methylbutyrate and several metabolites indicating accumulation and subsequent metabolism of methacrylyl-CoA and acryloyl-CoA. The metabolites derived from acryloyl-CoA were also increased in patients with inborn errors of propionyl-CoA metabolism, indicating the involvement of a secondary propionyl-CoA pathway utilising 3-hydroxyisobutyryl-CoA hydrolase. With the exception of 3-hydroxyisobutyryl carnitine, the metabolite abnormalities were essentially the same as those observed in patients with ECHS1 mutations, a recently described disorder that also affects valine metabolism. Our findings demonstrate the benefits of urine tandem mass spectrometry screening for diagnosing HIBCH and ECHS1 defects and that propionate metabolism may play a role in their pathogenesis. These disorders should be considered during the differential diagnosis of Leigh like-diseases and hypotonia.

An audit of newborn screening procedure: impact on infants presenting clinically before results are available

BACKGROUND AND OBJECTIVE

Tandem mass spectrometry-based newborn screening (NBS) is a powerful screening tool. The NBS process includes sample collection, shipment, testing, analysis, reporting and communication with the infant's family. We explored the NBS programme-related factors that may delay diagnosis and may influence timely initiation of treatment in neonates who present before the screening results are available and therefore urgently need diagnosis and treatment.

STUDY DESIGN

Detailed retrospective review of all data regarding sampling, shipment, testing and notification, contact with family and initiation of treatment of all neonates with disorders of fatty acid oxidation (FAO) and protein metabolism (PM), who presented clinically before NBS results were available, between 1-February-2002 and 31-January-2014.

RESULTS

Of 847,418 newborns screened, 18 infants presented clinically before NBS results were available (FAO n = 9, median age 2.5 days; PM n = 9, median age 3 days). Samples were collected from 11 infants at age 48-72 h, as per instructions, and were received in the laboratory at a median age of 7 days (median 4 days from sample collection until receipt in the laboratory). Results were available within 24h in 16/18 infants. Treatment for a suspected metabolic disorder was initiated in seven infants before results were available.

CONCLUSIONS

An audit of the programme procedures enabled the identification of issues that can be improved. Some patients benefited from the availability of results shortly after presentation. Good communication between the laboratory, the clinical metabolic specialist service and the primary treating team ensures timely initiation of treatment in these infants.

The utility of dried blood spots for proteomic studies: looking forward to looking back

The possibility to detect biomarkers of adult disease in early life and particularly in newborns holds enormous promise for early disease detection and prevention. Early detection of disease or potential for future disease would allow for prevention or amelioration of disease before overt symptoms develop, by lifestyle modifications, appropriate medication and monitoring. It is now increasingly important to develop the technologies that allow dried blood spots (DBS) to be utilized for protein-based studies. The use of DBS in proteome wide association studies (PWAS) may in turn allow for detection of major diseases of adulthood at the earliest possible time. This review focuses on the utility of DBS in proteomics, the main challenges, as well as the latest approaches for overcoming those, facilitating the use of DBS for detection of major diseases of adulthood at the earliest possible time.

Biochemical and molecular characteristics of patients with organic acidaemias and urea cycle disorders identified through newborn screening

BACKGROUND

In recent years it has become clear that newborn screening (NBS) programmes using tandem mass spectrometry identify "patients" with "classical" inborn errors of metabolism who are asymptomatic. This observation raises issues regarding medicalization of "non-diseases," potentially unnecessary treatment and unnecessary anxiety to parents.

AIMS

This study aims to identify possible markers that may assist in predicting the need for treatment of infants with "classical" organic acidaemias (OA) and urea cycle disorders (UCD) diagnosed through NBS.

METHODS

Medical records of all patients with classical OA and UCD detected through the Victorian NBS programme from February 2002 to January 2014, or diagnosed clinically between 1990 and January 2002 were retrospectively reviewed.

RESULTS

Neonatal presentation did not always predict the need for on-going strict treatment. Blood concentrations of amino acids and acyl-carnitines and the changes thereof in follow-up samples correlated with severity in citrullinaemia-I, possibly isovaleric acidaemia but not in argininosuccinic aciduria or propionic acidaemia. Some specific mutations correlate with "attenuated" citrullinaemia-I. Gender may affect clinical outcome in propionic acidaemia.

CONCLUSIONS

Changes in blood concentration of certain metabolites (amino acids, acyl-carnitines) in the first weeks of life may be predictive of the need for treatment in some disorders but not in others. Mutation analysis may be predictive in some disorders but whether or not this should be considered as second-tier testing in NBS should be discussed separately.

Implementation of written consent for newborn screening in Victoria, Australia

AIMS

There has been increasing evidence of a lack of public awareness of newborn screening and concern about inadequate consent being obtained from parents. Apprehension also exists in relation to storage and secondary use of screening samples. Our objective was to introduce a written consent process across Victoria as a means of strengthening programme transparency, quality and supporting parental choice. In addition, more comprehensive information covering all aspects of the programme was developed.

METHODS

A 'two-stage' written consent protocol allowed parents to give separate consent for (i) their baby to be screened and (ii) secondary use of the sample in de-identified health research. At the time of sample collection, parents were asked to complete the consent form, included as part of the screening card. The protocol was piloted in four public hospitals and subsequently implemented statewide.

RESULTS

Twelve months of laboratory data showed that although refusals for screening increased, overall participation remained above 99%. The percentage of parents opting out of research use was 6.5%. Provider compliance with the new protocol was high, with only 1.4% of cards received without a completed consent form.

CONCLUSION

This quality improvement project has demonstrated that parents can participate more fully in newborn screening without jeopardising high uptake. As a secondary benefit, the public health resource of stored cards can be maintained with parental support. Future work needs to examine the quality of consent being given by parents and investigation of the reasons why some choose to decline.

Mitochondrial carbonic anhydrase VA deficiency resulting from CA5A alterations presents with hyperammonemia in early childhood

Four children in three unrelated families (one consanguineous) presented with lethargy, hyperlactatemia, and hyperammonemia of unexplained origin during the neonatal period and early childhood. We identified and validated three different CA5A alterations, including a homozygous missense mutation (c.697T>C) in two siblings, a homozygous splice site mutation (c.555G>A) leading to skipping of exon 4, and a homozygous 4 kb deletion of exon 6. The deleterious nature of the homozygous mutation c.697T>C (p.Ser233Pro) was demonstrated by reduced enzymatic activity and increased temperature sensitivity. Carbonic anhydrase VA (CA-VA) was absent in liver in the child with the homozygous exon 6 deletion. The metabolite profiles in the affected individuals fit CA-VA deficiency, showing evidence of impaired provision of bicarbonate to the four enzymes that participate in key pathways in intermediary metabolism: carbamoylphosphate synthetase 1 (urea cycle), pyruvate carboxylase (anaplerosis, gluconeogenesis), propionyl-CoA carboxylase, and 3-methylcrotonyl-CoA carboxylase (branched chain amino acids catabolism). In the three children who were administered carglumic acid, hyperammonemia resolved. CA-VA deficiency should therefore be added to urea cycle defects, organic acidurias, and pyruvate carboxylase deficiency as a treatable condition in the differential diagnosis of hyperammonemia in the neonate and young child.

Hyperexcretion of homocitrulline in a Malaysian patient with lysinuric protein intolerance

Lysinuric protein intolerance (LPI; MIM 222700) is an inherited aminoaciduria with an autosomal recessive mode of inheritance. Biochemically, affected patients present with increased excretion of the cationic amino acids: lysine, arginine, and ornithine. We report the first case of LPI diagnosed in Malaysia presented with excessive excretion of homocitrulline. The patient was a 4-year-old male who presented with delayed milestones, recurrent diarrhea, and severe failure to thrive. He developed hyperammonemic coma following a forced protein-rich diet. Plasma amino acid analysis showed increased glutamine, alanine, and citrulline but decreased lysine, arginine and ornithine. Urine amino acids showed a marked excretion of lysine and ornithine together with a large peak of unknown metabolite which was subsequently identified as homocitrulline by tandem mass spectrometry. Molecular analysis confirmed a previously unreported homozygous mutation at exon 1 (235 G > A, p.Gly79Arg) in the SLC7A7 gene. This report demonstrates a novel mutation in the SLC7A7 gene in this rare inborn error of diamino acid metabolism. It also highlights the importance of early and efficient treatment of infections and dehydration in these patients.

CONCLUSION

The diagnosis of LPI is usually not suspected by clinical findings alone, and specific laboratory investigations and molecular analysis are important to get a definitive diagnosis.

Going back to the future with Guthrie-powered epigenome-wide association studies

Epigenome-wide association studies (EWAS) can be used to investigate links between early life environment, epigenetics and disease. However, such studies raise the question of which came first: the mark or the malady? A recent study has demonstrated that EWAS can be performed on neonatal 'Guthrie' heel-prick blood spots. As Guthrie cards are collected from all newborn infants and stored indefinitely in many countries, they represent an important timepoint to compare with later disease-associated epigenetic marks.