Consensus guidelines for the diagnosis and management of isolated sulfite oxidase deficiency and molybdenum cofactor deficiencies.

Sulfite intoxication is the hallmark of four ultrarare disorders that are caused by impaired sulfite oxidase activity due to genetic defects in the synthesis of the molybdenum cofactor or of the apoenzyme sulfite oxidase. Delays on the diagnosis of these disorders are common and have been caused by their unspecific presentation of acute neonatal encephalopathy with high early mortality, followed by the evolution of dystonic cerebral palsy and also by the lack of easily available and reliable diagnostic tests. There is significant variation in survival and in the quality of symptomatic management of affected children. One of the four disorders, molybdenum cofactor deficiency type A (MoCD-A) has recently become amenable to causal treatment with synthetic cPMP (fosdenopterin). The evidence base for the rational use of cPMP is very limited. This prompted the formulation of these clinical guidelines to facilitate diagnosis and support the management of patients. The guidelines were developed by experts in diagnosis and treatment of sulfite intoxication disorders. It reflects expert consensus opinion and evidence from a systematic literature search.

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 ß-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 ß-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 ß-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.

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.

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.

The Utility and Diagnostic Accuracy of Transient Elastography in Adults with Morbid Obesity: A Prospective Study.

Patients with morbid obesity are at high risk for nonalcoholic fatty liver disease (NAFLD) complicated by liver fibrosis. The clinical utility of transient elastography (TE) by Fibroscan in patients with morbid obesity (body mass index (BMI) ≥ 40 kg/m2) is not well-defined. We examined the diagnostic accuracy of Fibroscan in predicting significant liver fibrosis (fibrosis stage ≥2) in morbidly obese patients (BMI ≥ 40 kg/m2). Patients scheduled for bariatric surgery were prospectively enrolled. Intraoperative liver biopsy, liver-stiffness measurement (LSM) by Fibroscan (XL probe), and biochemical evaluation were all performed on the same day. The endpoint was significant liver fibrosis defined as fibrosis stage ≥2 based on the Nonalcoholic Steatohepatitis Clinical Research Network. The optimal LSM cutoff value for detecting significant fibrosis was determined by using the Youden Index method. Routine clinical, laboratory, and elastography data were analyzed by stepwise logistic regression analysis to identify predictors of significant liver fibrosis and build a predictive model. An optimal cutoff point of the new model's regression formula for predicting significant fibrosis was determined by using the Youden index method. One hundred sixty-seven patients (mean age, 46.4 years) were included, of whom 83.2% were female. Histological assessment revealed the prevalence of steatohepatitis and significant fibrosis of 40.7% and 11.4%, respectively. The median LSM was found to be significantly higher in the significant fibrosis group compared to those in the no or non-significant fibrosis group (18.2 vs. 7.7 kPa, respectively; p = 0.0004). The optimal LSM cutoff for predicting significant fibrosis was 12.8 kPa, with an accuracy of 71.3%, sensitivity of 73.7%, specificity of 70.9%, positive predictive value of 24.6%, negative predictive value of 95.5%, and ROC area of 0.723 (95% CI: 0.62-0.83). Logistic regression analysis identified three independent predictors of significant fibrosis: LSM, hemoglobin A1c, and alkaline phosphatase. A risk score was developed by using these three variables. At an optimal cutoff value of the regression formula, the risk score had an accuracy of 79.6% for predicting significant fibrosis, sensitivity of 89.5%, specificity of 78.4%, positive predictive value of 34.7%, negative predictive value of 98.3%, and ROC area of 0.855 (95% CI: 0.76-0.95). Fibroscan utility in predicting significant liver fibrosis in morbidly obese subjects is limited with accuracy of 71.3%. A model incorporating hemoglobin A1c and alkaline phosphatase with LSM improves accuracy in detecting significant fibrosis in this patient population.

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.

Compromised hepatic mitochondrial fatty acid oxidation and reduced markers of mitochondrial turnover in human NAFLD.

BACKGROUND AND AIMS: NAFLD and its more-advanced form, steatohepatitis (NASH), is associated with obesity and is an independent risk factor for cardiovascular, liver-related, and all-cause mortality. Available human data examining hepatic mitochondrial fatty acid oxidation (FAO) and hepatic mitochondrial turnover in NAFLD and NASH are scant. APPROACH AND RESULTS: To investigate this relationship, liver biopsies were obtained from patients with obesity undergoing bariatric surgery and data clustered into four groups based on hepatic histopathological classification: Control (CTRL; no disease); NAFL (steatosis only); Borderline-NASH (steatosis with lobular inflammation or hepatocellular ballooning); and Definite-NASH (D-NASH; steatosis, lobular inflammation, and hepatocellular ballooning). Hepatic mitochondrial complete FAO to CO2 and the rate-limiting enzyme in ß-oxidation (ß-hydroxyacyl-CoA dehydrogenase activity) were reduced by ~40%-50% with D-NASH compared with CTRL. This corresponded with increased hepatic mitochondrial reactive oxygen species production, as well as dramatic reductions in markers of mitochondrial biogenesis, autophagy, mitophagy, fission, and fusion in NAFL and NASH. CONCLUSIONS: These findings suggest that compromised hepatic FAO and mitochondrial turnover are intimately linked to increasing NAFLD severity in patients with obesity.

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.

A Model Incorporating Serum Alkaline Phosphatase for Prediction of Liver Fibrosis in Adults with Obesity and Nonalcoholic Fatty Liver Disease.

We assessed the relationship between serum alkaline phosphatase (ALP) and liver fibrosis by histology, in addition to other noninvasive parameters, in obese patients undergoing metabolic surgery. Patients scheduled for elective bariatric surgery were prospectively recruited from a bariatric clinic. An intraoperative liver biopsy was performed, and liver histology was evaluated by a pathologist blinded to the patients' data. The endpoint was significant fibrosis defined as fibrosis stage ≥ 2. Independent predictors of fibrosis were identified by logistic regression. Two hundred ten patients were recruited. Liver histology revealed steatosis in 87.1%, steatohepatitis in 21.9%, and significant fibrosis in 10%. Independent predictors of significant fibrosis were ALP (Odds Ratio (OR) 1.03; 95% Confidence interval (CI), 1.01-1.05), alanine aminotransferase (OR 1.02; 95% CI, 1.01-1.03), HbA1c (OR 1.58; 95% CI, 1.20-2.09), and body mass index (OR 1.06; 95% CI, 1.00-1.13). A tree-based model was developed to predict significant fibrosis, with a receiver operating characteristic (ROC) area of 0.845, sensitivity of 0.857, specificity of 0.836, and accuracy of 0.931. The applicability of serum ALP as an independent biomarker of liver fibrosis should be considered in obesity surgery patients, and in the broader context of obese patients with nonalcoholic fatty liver disease.

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.

Newborn bloodspot screening in the time of COVID-19.

PURPOSE: A COVID-19 pandemic business continuity plan (BCP) was rapidly developed to protect the Victorian newborn screening (NBS) program. Here, we present the outcomes of our COVID-19 BCP and its impact on the Victorian NBS laboratory service. METHODS: Change management principles were used to develop a BCP that included mapping of NBS processes against staff resources, triaging priorities, technology solutions, supply chain continuity, gap analysis, and supporting maternity service providers. The effect was assessed quantitatively by review of key performance indicator data and qualitatively from staff feedback. RESULTS: A four-stage BCP was implemented. Stage 1 split teams into two, which rotated weekly, onsite (laboratory) and offsite (home). At 20 weeks post-implementation the BCP only progressed to stage 1 and the overall turnaround time was maintained. Staff experience indicated benefits from the review of workflow but noted some social impact associated with the change. CONCLUSION: The preparedness and agility of implementation was based on our focus on the newborn babies and their families, our production system, and a continuous improvement mindset. Both our people and technology infrastructure processes are crucial to this success as we continue to adapt to new challenges.

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.