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Background Phosphatidylinositol glycan biosynthesis class A protein (PIGA) is one of the enzymes involved in the biosynthesis of glycosylphosphatidylinositol (GPI) anchor proteins, which function as enzymes, adhesion molecules, complement regulators and co-receptors in signal transduction pathways. Until recently, only somatic PIGA mutations had been reported in patients with paroxysmal nocturnal hemoglobinuria (PNH), while germline mutations had not been observed, and were suspected to result in lethality. However, in just two years, whole exome sequencing (WES) analyses have identified germline PIGA mutations in male patients with XLIDD (X-linked intellectual developmental disorder) with a wide spectrum of clinical presentations. Methods and results Here, we report on a new missense PIGA germline mutation [g.15342986C>T (p.S330N)] identified via WES followed by Sanger sequencing, in a Chinese male infant presenting with developmental arrest, infantile spasms, a pattern of lesion distribution on brain MRI resembling that typical of maple syrup urine disease, contractures, dysmorphism, elevated alkaline phosphatase, mixed hearing loss (a combination of conductive and sensorineural), liver dysfunction, mitochondrial complex I and V deficiency, and therapy-responsive dyslipidemia with confirmed lipoprotein lipase deficiency. X-inactivation studies showed skewing in the clinically unaffected carrier mother, and CD109 surface expression in patient fibroblasts was 57% of that measured in controls; together these data support pathogenicity of this mutation. Furthermore, we review all reported germline PIGA mutations (1 nonsense, 1 frameshift, 1 in-frame deletion, five missense) in 8 unrelated families. Conclusions Our case further delineates the heterogeneous phenotype of this condition for which we propose the term ‘PIGA deficiency’. While the phenotypic spectrum is wide, it could be classified into two types (severe and less severe) with shared hallmarks of infantile spasms with hypsarrhythmia on EEG and profound XLIDD. In severe PIGA deficiency, as described in our patient, patients also present with dysmorphic facial features, multiple CNS abnormalities, such as thin corpus callosum and delayed myelination, as well as hypotonia and elevated alkaline phosphatase along with liver, renal, and cardiac involvement; its course is often fatal. The less severe form of PIGA deficiency does not involve facial dysmorphism and multiple CNS abnormalities; instead, patients present with milder IDD, treatable seizures and generally a longer lifespan.

Gamma-butyrobetaine hydroxylase (BBOX1) catalyses the last step of carnitine biosynthesis, converting γ-butyrobetaine (γ-BB) into L-carnitine. Here we show, for the first time, that biallelic variants in BBOX1 are associated with decreased levels of L-carnitine and increased plasma levels of γ-BB in three patients from two unrelated families presenting with myopathic, neurodevelopmental, and late-onset psychiatric manifestations. Using a knockout C. elegans model of BBOX1 homolog, gbh-1 , and strains harboring patient-derived variants ( gbh-1(D72G) for p.Asp59Gly, gbh-1(G283R) for p.Gly263Arg, and gbh-1(G247Vfs6) for p.Gly227Valfs*6), we show very low L-carnitine levels and significantly elevated γ-BB in c.675delA and c.787G>A mutants, and moderately elevated γ-BB in c.176A>G. Furthermore, we observed a lethal embryonic phenotype for the gbh-1 loss-of-function strains, which was rescued upon L-carnitine supplementation. Our study provides novel insights into the clinical and biochemical consequences of BBOX1-related L-carnitine biosynthesis deficiency and establishes C. elegans as a model to study the effects of BBOX1 deficiency.

This study aimed (1) to explore the association between body composition [fat-to-muscle ratio (FMR), waist circumference (WC), and body mass index (BMI)] with motor competence (MC) and physical fitness (PFI) in 7-year-old children; (2) to ascertain whether FMR modifies the associations between MC and PF. A total of 164 children (7 yr) were included. Anthropometric (fat and muscle mass were calculated with TANITA), motor competence (CAMSA test) and physical fitness (1/2 mile run, handgrip strength, 10 × 5, standing long jump, and sit and reach tests) variables were collected. FMR, WC and BMI correlated negatively with MC (all between r ≤ −0.333 and −0.183 and p < 0.05) and PFI (all between r ≤ −0.410 and −0.246 and p < 0.05) in all children. However, the associations were stronger for FMR. In linear regressions analyses, only FMR was independently and negatively associated with MC and PFI, explaining 12.6% and 20.9% of its variance, respectively. Positive correlations between PFI and MC existed. Also, the association was not modified by FMR levels, since in both groups (above and below FMR median), the associations were maintained (p < 0.0001). However, the t-test showed that children with higher FMRs have lower levels of MC (p = 0.005) and PFI (p < 0.0001). FMR may be the best body composition parameter related to MC and PFI. Furthermore, the association between MC and PFI is not modulated by FMR but children with higher FMRs show lower levels of MC and PFI.

Vitamin B12 (B12) is a co-enzyme essential for fetal growth and development. Lower maternal B12 status has been associated with preterm birth (<37 gestational weeks) and low birth weight (<2500 g), which are linked to morbidity and mortality across the lifespan. In Canada, 17–25 % of women in early pregnancy had a serum total B12 concentration <148 pmol/l and maternal total B12 concentration decreased throughout pregnancy. This study aimed to determine the association between maternal B12 status and birth outcomes in Canadian mother–newborn dyads. A secondary analysis of 709 mother–newborn dyads in British Columbia (BC), Canada, was conducted. Bio-banked first- (n 656) and second-trimester (n 709) maternal serum samples of apparently healthy South Asian (50 %) and European (50 %) women from the BC Prenatal Genetic Screening Program were quantified for B12 biomarkers (total B12, holotranscobalamin (holoTC), methylmalonic acid (MMA) and total homocysteine (tHcy)). Obstetric history and birth outcome data were obtained from the BC Perinatal Data Registry. All associations were determined using multiple linear regression. Maternal serum total B12, holoTC, MMA and tHcy had a mean weekly decrease of 3·64 pmol/l, 1·04 pmol/l, 1·44 nmol/l and 0·104 μmol/l, respectively (P < 0·001). Despite a total B12 concentration <148 pmol/l among 20–25 % of the women, maternal B12 biomarker concentrations were not associated with birth weight z-score, head circumference z-score and gestational age at birth (P > 0·05). Additional research in women at high risk of adverse birth outcomes and the association between maternal B12 status and functional, for example, cognitive, outcomes is needed.

Vitamin B 12 (B 12 ) is a co-enzyme essential for fetal growth and development. Lower maternal B 12 status has been associated with preterm birth (<37 gestational weeks) and low birth weight (<2500 g), which are linked to morbidity and mortality across the lifespan. In Canada, 17–25 % of women in early pregnancy had a serum total B 12 concentration <148 pmol/l and maternal total B 12 concentration decreased throughout pregnancy. This study aimed to determine the association between maternal B 12 status and birth outcomes in Canadian mother–newborn dyads. A secondary analysis of 709 mother–newborn dyads in British Columbia (BC), Canada, was conducted. Bio-banked first- ( n 656) and second-trimester ( n 709) maternal serum samples of apparently healthy South Asian (50 %) and European (50 %) women from the BC Prenatal Genetic Screening Program were quantified for B 12 biomarkers (total B 12 , holotranscobalamin (holoTC), methylmalonic acid (MMA) and total homocysteine (tHcy)). Obstetric history and birth outcome data were obtained from the BC Perinatal Data Registry. All associations were determined using multiple linear regression. Maternal serum total B 12 , holoTC, MMA and tHcy had a mean weekly decrease of 3·64 pmol/l, 1·04 pmol/l, 1·44 nmol/l and 0·104 μmol/l, respectively ( P < 0·001). Despite a total B 12 concentration <148 pmol/l among 20–25 % of the women, maternal B 12 biomarker concentrations were not associated with birth weight z -score, head circumference z -score and gestational age at birth ( P > 0·05). Additional research in women at high risk of adverse birth outcomes and the association between maternal B 12 status and functional, for example, cognitive, outcomes is needed.

Abstract Global developmental delay and intellectual disability (GDD/ID) affect 3% of the paediatric population. Although inborn errors of metabolism (IEM) are not a common cause of GDD/ID, early therapeutic intervention can improve neurodevelopmental manifestations. In 2012, a first-tier test panel, including specialized metabolic and routine chemistry tests, was piloted to community-based paediatricians in British Columbia with aims to achieve earlier diagnosis of treatable IEM. Objective The aim of this retrospective review was to evaluate the diagnostic yield from these first-tier tests in the 7 years before (2006 to 2012) and after (2013 to 2019) implementation at the community paediatrician level. Results Prior and postimplementation diagnostic yield of an IEM from first-tier metabolic testing was 9 out of 986 (0.91%) and 11 out of 4,345 children (0.25%), respectively. Disorders of creatine metabolism and organic acidurias were the most frequently established diagnoses in both time periods. No diagnoses were established through acylcarnitine copper/ceruloplasmin, lactate, or ammonia testing. Twenty out of 24 patients had specific neurological or other red flag signs in addition to GDD/ID. Four boys diagnosed with an x-linked creatine transporter defect (CTD) had speech-language delay as the most prominent finding. Conclusions The expansion of first-tier metabolic testing to community-based paediatricians in BC did not yield an increase in IEM diagnoses. A modified first-tier test panel should be offered to patients with GDD/ID, neurologic, and/or red flag signs. Urine creatine testing in boys with speech-language delay warrants consideration to detect CTD.

Background The presence of ketone bodies (KBs) can interfere with creatinine (Cr) measurement in both enzymatic and Jaffe methods. Since a high proportion of children hospitalized for diabetic ketoacidosis (DKA) develop acute kidney injury (AKI), here we investigate whether KB interferences affect the accuracy of pediatric Cr measurement. Methods Residual patient plasma samples were pooled to make three Cr levels (~ 50, 100, and 250 μM). KBs (acetone, acetoacetate, and β-hydroxybutyrate) were used to spike the pooled samples. All samples were measured for Cr by two enzymatic methods (E1 and E2), two Jaffe methods (J1 and J2), and LC–MS/MS. LC–MS/MS was considered the gold standard, and the % difference in Cr concentration was calculated for each method. Results E1 and E2 were unaffected by the presence of all three KBs. J1 and J2 were unaffected by the presence of β-hydroxybutyrate. The presence of acetone resulted in dose-dependent positive interference in both Jaffe methods, whereas the presence of acetoacetate resulted in dose-dependent positive and negative interference in J1 and J2, respectively. Conclusions Compared to the enzymatic methods, the Jaffe methods were much more susceptible to interference by acetone and acetoacetate, especially at lower Cr values which are commonly seen in pediatrics. Interpretation of changes in Cr concentration between different hospitals when transferring patients can become ambiguous and true kidney function unclear if different methods are used without awareness of method-specific biases. To improve DKA patient care, we recommend standardizing all of the Cr methods to an enzymatic method. Graphical abstract A higher resolution version of the Graphical abstract is available as Supplementary information

BackgroundOxythiamine is a uremic toxin that acts as an antimetabolite to thiamine and has been associated with cases of Shoshin beriberi syndrome in adults. We sought to identify whether surgical stress and ischemia/reperfusion injury may precipitate functional thiamine deficiency in children peritransplant.MethodsWe retrospectively analyzed a cohort of pediatric kidney transplant recipients. Oxythiamine levels were measured in pre-transplant serum samples by mass spectrometry and tested for association with severity of lactic acidosis in the first 24 h post-transplant. Secondary outcomes included association with hyperglycemia and indicators of dialysis adequacy (DA).ResultsForty-seven patients were included in the analysis. Median oxythiamine levels differed by modality, measuring 0.67 nM (IQR 0.31, 0.74), 0.34 nM (IQR 0.28, 0.56), and 0.25 nM (IQR 0.17, 0.38) for peritoneal dialysis (PD), hemodialysis (HD), and no dialysis, respectively (p = 0.05). Oxythiamine was associated with 24-h lactate levels (r = 0.38, p = 0.02) and negatively associated with DA (r = − 0.44, p = 0.02). Median oxythiamine levels were higher in patients with poor DA (0.92 nM (IQR 0.51, 1.01) vs. 0.40 nM (IQR 0.24, 0.51), p < 0.01). Sensitivity analysis showed absence of residual association of oxythiamine with 24-h lactate or dialysis modality, but remained significant for DA (p = 0.03). One patient manifested Shoshin beriberi syndrome (oxythiamine 2.03 nM).ConclusionsOxythiamine levels are associated with DA at transplant. Patients on PD with no residual kidney function and low DA manifest the highest oxythiamine levels and may be at an increased risk for developing acute Shoshin beriberi syndrome in the early post-transplant period.

Abstract Background The hepatic carnitine palmitoyltransferase I (CPT1A) p.P479L variant is common in Aboriginal populations across coastal British Columbia, Alaska, the Canadian North, and Greenland. While the high frequency of this variant suggests positive selection, other studies have shown an association with sudden unexpected death in infancy and infection. We utilized administrative health data to evaluate hospitalizations for a single year cohort of children of First Nations descent genotyped for the variant and, matched for location of birth. Seven years of data were reviewed for 150 children split evenly between CPT1A genotypes (homozyous, heterozygous, and noncarrier of the p.P479L variant). Results Children homozygous for the p.P479L allele had a higher rate of hospital admissions at 2.6 per individual as compared to noncarriers at 0.86. Heterozygous children also showed a significant increase at 1.9 per person. Length of stay per admission was increased for both p.P479L homozygotes and heterozygotes. The odds ratio (OR) for at least one hospitalization for any reason was increased for p.P479L homozygotes relative to noncarriers (OR=10.2, confidence interval [CI] 3.5 to 30.0) as were admissions for dental caries (OR=3.4, CI 1.5 to 7.8), acute lower respiratory tract infections (OR=6.0, CI 1.6 to 22.4), and otitis media (OR=13.5, CI 1.7 to 109.4). Conclusions The CPT1A p.P479L variant is associated with an increased rate of hospitalization for those homozygous, primarily for infectious disease causes. Heterozygotes also showed a small but significant increase in hospitalization rates suggesting some dosage effect. Functional studies will be required to identify the underlying pathological mechanism.

BackgroundDysfunction of histone methyltransferases and chromatin modifiers has been implicated in complex neurodevelopmental syndromes and cancers. SETD1B encodes a lysine-specific methyltransferase that assists in transcriptional activation of genes by depositing H3K4 methyl marks. Previous reports of patients with rare variants in SETD1B describe a distinctive phenotype that includes seizures, global developmental delay and intellectual disability.MethodsTwo of the patients described herein were identified via genome-wide and exome-wide testing, with microarray and research-based exome, through the CAUSES (Clinical Assessment of the Utility of Sequencing and Evaluation as a Service) Research Clinic at the University of British Columbia. The third Vancouver patient had clinical trio exome sequencing through Blueprint Genetics. The fourth patient underwent singleton exome sequencing in Nantes, with subsequent recruitment to this cohort through GeneMatcher.ResultsHere we present clinical reports of four patients with rare coding variants in SETD1B that demonstrate a shared phenotype, including intellectual disability, language delay, conserved musculoskeletal findings and seizures that may be treatment-refractory. We include supporting evidence from next-generation sequencing among a cohort of paediatric patients with epilepsy.ConclusionRare coding variants in SETD1B can cause a diagnosable syndrome and could contribute as a risk factor for epilepsy, autism and other neurodevelopmental phenotypes. In the long term, some patients may also be at increased risk for cancers and other complex diseases. Thus, longitudinal studies are required to further elucidate the precise role of SETD1B in neurodevelopmental disorders and other systemic disease.