Disentangling molecular and clinical stratification patterns in beta-galactosidase deficiency.

INTRODUCTION: This study aims to define the phenotypic and molecular spectrum of the two clinical forms of ß-galactosidase (ß-GAL) deficiency, GM1-gangliosidosis and mucopolysaccharidosis IVB (Morquio disease type B, MPSIVB). METHODS: Clinical and genetic data of 52 probands, 47 patients with GM1-gangliosidosis and 5 patients with MPSIVB were analysed. RESULTS: The clinical presentations in patients with GM1-gangliosidosis are consistent with a phenotypic continuum ranging from a severe antenatal form with hydrops fetalis to an adult form with an extrapyramidal syndrome. Molecular studies evidenced 47 variants located throughout the sequence of the GLB1 gene, in all exons except 7, 11 and 12. Eighteen novel variants (15 substitutions and 3 deletions) were identified. Several variants were linked specifically to early-onset GM1-gangliosidosis, late-onset GM1-gangliosidosis or MPSIVB phenotypes. This integrative molecular and clinical stratification suggests a variant-driven patient assignment to a given clinical and severity group. CONCLUSION: This study reports one of the largest series of b-GAL deficiency with an integrative patient stratification combining molecular and clinical features. This work contributes to expand the community knowledge regarding the molecular and clinical landscapes of b-GAL deficiency for a better patient management.

Heterogenous Clinical Landscape in a Consanguineous Malonic Aciduria Family.

Malonic aciduria is an extremely rare inborn error of metabolism due to malonyl-CoA decarboxylase deficiency. This enzyme is encoded by the MLYCD (Malonyl-CoA Decarboxylase) gene, and the disease has an autosomal recessive inheritance. Malonic aciduria is characterized by systemic clinical involvement, including neurologic and digestive symptoms, metabolic acidosis, hypoglycemia, failure to thrive, seizures, developmental delay, and cardiomyopathy. We describe here two index cases belonging to the same family that, despite an identical genotype, present very different clinical pictures. The first case is a boy with neonatal metabolic symptoms, abnormal brain MRI, and dilated cardiomyopathy. The second case, the cousin of the first patient in a consanguineous family, showed later symptoms, mainly with developmental delay. Both patients showed high levels of malonylcarnitine on acylcarnitine profiles and malonic acid on urinary organic acid chromatographies. The same homozygous pathogenic variant was identified, c.346C > T; p. (Gln116*). We also provide a comprehensive literature review of reported cases. A review of the literature yielded 52 cases described since 1984. The most common signs were developmental delay and cardiomyopathy. Increased levels of malonic acid and malonylcarnitine were constant. Presentations ranged from neonatal death to patients surviving past adolescence. These two cases and reported patients in the literature highlight the inter- and intrafamilial variability of malonic aciduria.

Thrombin generation test as a marker for high risk venous thrombosis pregnancies.

Pregnancy is a well-established risk factor for venous thromboembolism and is associated with a state of hypercoagulability. The use of sensitive and specific biological markers to predict risk factors for thrombosis is essential during pregnancy. Our objective was to investigate the usefulness of thrombin generation test (TGT) as a marker to predict the risk of thrombosis in high risk venous thrombosis (HRVT) pregnancies compared to normal pregnancies. This retrospective study enrolled 134 women with HRVT pregnancies, 78 of whom had monozygotic, spontaneous and untreated pregnancies and formed the study group. The control group comprised 106 women with normal pregnancies. Routine assessment of coagulation activation markers: fibrinogen, D-dimer, prothrombin fragments 1 + 2 (F1 + 2), thrombin-antithrombin complexes (TAT) and fibrin monomer complexes (FMC) was performed every 5 weeks in the study group to detect a possible pathological state of hypercoagulability. TGT was performed using platelet-free plasma, 1 and 5 pM tissue factor (TF), supplemented by phospholipids (PL) ± thrombomodulin. Fibrinogen, D-dimer, F1 + 2, and TAT, but not FMC, increased significantly throughout pregnancy in both groups but no difference was shown between the groups. TGT showed an early increase in thrombin generation in both groups, which stabilized during the second month of pregnancy. No correlation was demonstrated between thrombin generation parameters and coagulation activation markers. Based on our results, TGT did not prove conclusive as a marker to predict the risk of thrombosis in HRVT pregnancies. Finding a sensitive and specific biological marker to predict thrombosis risk requires further investigation.

Acute Respiratory Infection Unveiling CPT II Deficiency.

Carnitine Palmitoyl transferase 2 (CPT II) is involved in long-chain fatty-acid mitochondrial transport. Three clinical phenotypes of CPT II deficiency have been described: Lethal neonatal onset, infantile severe form, and the late onset more common muscular form. The muscular form of CPT II deficiency is characterized by pain crises and rhabdomyolysis triggered by energy-dependent factors. This form has been described as a benign condition; however, the acute crises are insidious and thus, pose a risk of death. We report a 3-year-old female child with an acute pulmonary infection and a concomitant rhabdomyolysis. The acylcarnitine profile was consistent with CPT II deficiency and a molecular study allowed the identification of the common missense variant (NM_000098.2: c.338C>T ⁻ p. Ser113Leu) at the homozygous state. The striking difference between the initial cause and the decompensation severity prompted us to consider other diagnoses. Deciphering the symptoms linked to CPT II deficiency among those of the initial decompensation results in initiating a timely a targeted therapy.

Methylmalonyl-CoA Epimerase Deficiency Mimicking Propionic Aciduria.

Methylmalonyl-CoA epimerase (MCE) converts d-methylmalonyl-CoA epimer to l-methylmalonyl-CoA epimer in the propionyl-CoA to succinyl-CoA pathway. Only seven cases of MCE deficiency have been described. In two cases, MCE deficiency was combined with sepiapterin reductase deficiency. The reported clinical pictures of isolated MCE are variable, with two asymptomatic patients and two other patients presenting with metabolic acidosis attacks. For combined MCE and sepiapterin reductase deficiency, the clinical picture is dominated by neurologic alterations. We report isolated MCE deficiency in a boy who presented at five years of age with acute metabolic acidosis. Metabolic investigations were consistent with propionic aciduria (PA). Unexpectedly, propionyl-CoA carboxylase activity was within the reference range. Afterward, apparently intermittent and mild excretion of methylmalonic acid (MMA) was discovered. Methylmalonic pathway gene set analysis using the next-generation sequencing approach allowed identification of the common homozygous nonsense pathogenic variant (c.139C > T-p.Arg47*) in the methylmalonyl-CoA epimerase gene (MCEE). Additional cases of MCE deficiency may help provide better insight regarding the clinical impact of this rare condition. MCE deficiency could be considered a cause of mild and intermittent increases in methylmalonic acid.

Implementation of a "hypoglycemia kit" in a pediatric emergency room: A retrospective study during 2011-2019.

INTRODUCTION: Hypoglycemia is a common symptom in pediatrics that can lead to neurological sequelae. The etiologies are mostly benign, but hypoglycemia can be a symptom of severe underlying disease. To streamline the etiological investigations, a "hypoglycemia kit," containing supplies needed to perform specific analyses quickly, was made available in the pediatric emergency department of the Rouen University Hospital in 2011. Since its introduction, this kit has been used to explore all cases of hypoglycemia regardless of the context. However, although very useful, these analyses are expensive. The objective of our study was to examine the cost-effectiveness of this kit and to refine its indications if necessary. METHODS: This was a non-interventional and retrospective single-center study. Digital records of patients for whom a hypoglycemia kit was used from September 2011 to August 2019 at the pediatric emergency department of Rouen University Hospital were used to retrieve clinical characteristics, laboratory results, and the causes of hypoglycemia. RESULTS: The study included 82 patients. The etiologic investigation concluded that 74 patients had functional hypoglycemia, and eight cases were attributed to other etiologies. In two cases, the kit led to a diagnosis, i.e., 2.4 % efficiency. A history of congenital malformations or previous hypoglycemia was significantly associated with severe etiologies. However, there was no significant association between hypoglycemia severity, age, sex, and these etiologies. CONCLUSION: Our study reveals that the cost-effectiveness of the hypoglycemia kit is low in pediatric emergencies (2.4 %) at Rouen University Hospital, where functional hypoglycemia remains the leading cause of hypoglycemia. However, our results allow us to suggest a decision tree for refining the usability of this kit, which would considerably increase its efficiency.

[A simple approach to create a common language, a necessary element for the development of a quality culture in a medical biology laboratory]. / Une approche simple pour créer un langage commun, élément nécessaire au développement d'une culture qualité au sein d'un laboratoire de biologie médicale.

The order no. 2010-49 of January 13, 2010 has made the accreditation of medical biology laboratories in France mandatory. It is based on international standards: NF EN ISO 15189 for medical biology laboratories and NF EN ISO 22870 for point-of-care testing. The NF EN ISO 15189:2012 standard is an adaptation of the requirements relating to the quality management system according to the ISO 9001:2008 standard, to improve delivery performance. As a company's performance is closely linked to its quality culture, the establishment and development of a quality culture within a company appears fundamental. The purpose of this article is to explain how to create a common language on which to base the development of quality culture within a medical biology laboratory. It is a simple approach which consists in asking 3 questions concerning quality management to the members of the team of this laboratory (what do you value? what emotions give you these values? what do you not value?) then to organize the answers in a reference frame for quality management.

An Atypical Case of Congenital Erythropoietic Porphyria.

Congenital erythropoietic porphyria (CEP, OMIM #606938) is a severe autosomal recessive inborn error of heme biosynthesis. This rare panethnic disease is due to a deficiency of uroporphyrinogen III synthase (or cosynthase). Subsequently, its substrate, the hydroxymethylbilane is subsequently converted into uroporphyrinogen I in a non-enzymatic manner. Of note, uroporphyrinogen I cannot be metabolized into heme and its accumulation in red blood cells results in intramedullary and intravascular hemolysis. The related clinical symptoms occur most frequently during antenatal or neonatal periods but may also appear in late adulthood. The main antenatal clinical presentation is a non-immune hydrops fetalis. We report here two cases of antenatal CEP deficiency and a review of the reported cases in the literature.

An Atypical Case of Head Tremor and Extensive White Matter in an Adult Female Caused by 3-Hydroxy-3-methylglutaryl-CoA Lyase Deficiency.

3-Hydroxy-3-methylglutaryl-CoA (HMG-CoA) Lyase deficiency (HMGLD) (OMIM 246450) is an autosomal recessive genetic disorder caused by homozygous or compound heterozygous variants in the HMGCL gene located on 1p36.11. Clinically, this disorder is characterized by a life-threatening metabolic intoxication with a presentation including severe hypoglycemia without ketosis, metabolic acidosis, hyper-ammoniemia, hepatomegaly and a coma. HMGLD clinical onset is within the first few months of life after a symptomatic free period. In nonacute periods, the treatment is based on a protein- and fat-restricted diet. L-carnitine supplementation is recommended. A late onset presentation has been described in very few cases, and only two adult cases have been reported. The present work aims to describe an incidental discovery of an HMGLD case in a 54-year-old patient and reports a comprehensive review of clinical and biological features in adult patients to raise awareness about the late-onset presentation of this disease.

NGLY1 Deficiency: A Rare Newly Described Condition with a Typical Presentation.

NGLY1 deficiency is the first recognized autosomal recessive disorder of N-linked deglycosylation (NGLY1-CDDG). This severe multisystemic disease is still poorly known and, to date, most cases have been diagnosed through whole exome or genome sequencing. The aim of this study is to provide the clinical, biochemical and molecular description of the first NGLY1-CDDG patient from France along with a literature review. The index case presented with developmental delay, acquired microcephaly, hypotonia, alacrimia, feeding difficulty, and dysmorphic features. Given the complex clinical picture and the multisystemic involvement, a trio-based exome sequencing was conducted and urine oligosaccharides were assessed using mass spectrometry. The exome sequencing revealed a novel variant in the NGLY1 gene in a homozygous state. NGLY1 deficiency was confirmed by the identification of the Neu5Ac1Hex1GlcNAc1-Asn oligosaccharide in the urine of the patient. Literature review revealed the association of some key clinical and biological features such as global developmental delay-hypertransaminasemia, movement disorders, feeding difficulties and alacrima/hypolacrima.

Next-Generation Molecular Investigations in Lysosomal Diseases: Clinical Integration of a Comprehensive Targeted Panel.

Diagnosis of lysosomal disorders (LDs) may be hampered by their clinical heterogeneity, phenotypic overlap, and variable age at onset. Conventional biological diagnostic procedures are based on a series of sequential investigations and require multiple sampling. Early diagnosis may allow for timely treatment and prevent clinical complications. In order to improve LDs diagnosis, we developed a capture-based next generation sequencing (NGS) panel allowing the detection of single nucleotide variants (SNVs), small insertions and deletions, and copy number variants (CNVs) in 51 genes related to LDs. The design of the LD panel covered at least coding regions, promoter region, and flanking intronic sequences for 51 genes. The validation of this panel consisted in testing 21 well-characterized samples and evaluating analytical and diagnostic performance metrics. Bioinformatics pipelines have been validated for SNVs, indels and CNVs. The clinical output of this panel was tested in five novel cases. This capture-based NGS panel provides an average coverage depth of 474× which allows the detection of SNVs and CNVs in one comprehensive assay. All the targeted regions were covered above the minimum required depth of 30×. To illustrate the clinical utility, five novel cases have been sequenced using this panel and the identified variants have been confirmed using Sanger sequencing or quantitative multiplex PCR of short fluorescent fragments (QMPSF). The application of NGS as first-line approach to analyze suspected LD cases may speed up the identification of alterations in LD-associated genes. NGS approaches combined with bioinformatics analyses, are a useful and cost-effective tool for identifying the causative variations in LDs.

Large-scale screening of lipase acid deficiency in at risk population.

BACKGROUND: Lysosomal acid lipase deficiency (LALD, OMIM#278000) is a rare lysosomal disorder with an autosomal recessive inheritance. The main clinical manifestations are related to a progressive accumulation of cholesteryl esters, triglycerides or both within the lysosome in different organs such as the liver, spleen, and cardiovascular system. A wide range of clinical severity is associated with LALD including a severe very rare antenatal/neonatal/infantile phenotype named Wolman disease and a late-onset form named cholesteryl ester storage disease (CESD). METHODS: This study aimed to investigate a cohort of at-risk patients (4174) presenting with clinical or biological signs consistent with LALD using the assessment of LAL activity on dried blood spots. RESULTS: LAL activity was lower than 0.05 nmol/punch/L (cut-off: 0.12) in 19 patients including 13 CESD and 6 Wolman. Molecular study has been conducted in 17 patients and succeeded in identifying 34 mutated alleles. Fourteen unique variants have been characterized, 7 of which are novel. CONCLUSION: This study allowed to identify a series of patients and expanded the molecular spectrum knowledge of LALD. Besides, a new screening criteria grid based on the clinical/biological data from our study and the literature has been proposed in order to enhance the diagnosis rate in at risk populations.

Metabolic causes of nonimmune hydrops fetalis: A next-generation sequencing panel as a first-line investigation.

PURPOSES: Hydrops fetalis is a life-threatening fetal condition, and 85% of all cases are classified as nonimmune hydrops fetalis (NIHF). Up to 15% of NIHF cases may be due to inborn errors of metabolism (IEM), but a large proportion of cases linked to metabolic disorders remains undiagnosed. This lack of diagnosis may be related to the limitations of conventional biological procedures, which involve sequential investigations and require multiple samples and steps. In addition, this approach is time consuming. We have developed a next-generation sequencing (NGS) panel to investigate metabolic causes of NIHF, ascites, and polyhydramnios associated to another fetal abnormality. METHODS: The hydrops fetalis (HydFet) panel was designed to cover the coding regions and flanking intronic sequences of 41 genes. A retrospective study of amniotic fluid samples from 40 subjects was conducted. A prospective study was subsequently initiated, and six samples were analyzed using the NGS panel. RESULTS: Five IEM diagnoses were made using the HydFet panel (Niemann-Pick type C (NPC), Barth syndrome, HNF1Β deficiency, GM1 gangliosidosis, and Gaucher disease). This analysis also allowed the identification of 8p sequence triplication in an additional case. CONCLUSION: NGS combined with robust bioinformatics analyses is a useful tool for identifying the causative variants of NIHF. Subsequent functional characterization of the protein encoded by the altered gene and morphological studies may confirm the diagnosis. This paradigm shift allows a significant improvement of IEM diagnosis in NIHF.

Clinical and molecular characterization of cystinuria in a French cohort: relevance of assessing large-scale rearrangements and splicing variants.

BACKGROUND: Cystinuria is an autosomal recessive disorder of dibasic amino acid transport in the kidney and the intestine leading to increased urinary cystine excretion and nephrolithiasis. Two genes, SLC3A1 and SLC7A9, coding respectively for rBAT and b0,+AT, account for the genetic basis of cystinuria. METHODS: This study reports the clinical and molecular characterization of a French cohort including 112 cystinuria patients and 25 relatives from 99 families. Molecular screening was performed using sequencing and Quantitative Multiplex PCR of Short Fluorescent Fragments analyses. Functional minigene-based assays have been used to characterize splicing variants. RESULTS: Eighty-eight pathogenic nucleotide changes were identified in SLC3A1 (63) and SLC7A9 (25) genes, of which 42 were novel. Interestingly, 17% (15/88) and 11% (10/88) of the total number of variants correspond, respectively, to large-scale rearrangements and splicing mutations. Functional minigene-based assays were performed for six variants located outside the most conserved sequences of the splice sites; three variants affect splice sites, while three others modify exonic splicing regulatory elements (ESR), in good agreement with a new in silico prediction based on ΔtESRseq values. CONCLUSION: This report expands the spectrum of SLC3A1 and SLC7A9 variants and supports that digenic inheritance is unlikely. Furthermore, it highlights the relevance of assessing large-scale rearrangements and splicing mutations to fully characterize cystinuria patients at the molecular level.