Oral sialic acid supplementation in NANS-CDG: Results of a single center, open-label, observational pilot study.

NANS-CDG is a congenital disorder of glycosylation (CDG) caused by biallelic variants in NANS, encoding an essential enzyme in de novo sialic acid synthesis. It presents with intellectual developmental disorder (IDD), skeletal dysplasia, neurologic impairment, and gastrointestinal dysfunction. Some patients suffer progressive intellectual neurologic deterioration (PIND), emphasizing the need for a therapy. In a previous study, sialic acid supplementation in knockout nansa zebrafish partially rescued skeletal abnormalities. Here, we performed the first in-human pre- and postnatal sialic-acid study in NANS-CDG. In this open-label observational study, 5 patients with NANS-CDG (range 0-28 years) were treated with oral sialic acid for 15 months. The primary outcome was safety. Secondary outcomes were psychomotor/cognitive testing, height and weight, seizure control, bone health, gastrointestinal symptoms, and biochemical and hematological parameters. Sialic acid was well tolerated. In postnatally treated patients, there was no significant improvement. For the prenatally treated patient, psychomotor and neurologic development was better than two other genotypically identical patients (one treated postnatally, one untreated). The effect of sialic acid treatment may depend on the timing, with prenatal treatment potentially benefiting neurodevelopmental outcomes. Evidence is limited, however, and longer-term follow-up in a larger number of prenatally treated patients is required.

Abnormal expression of lysosomal glycoproteins in patients with congenital disorders of glycosylation.

OBJECTIVE: The study of the impact of some inherited defects in glycosylation on the biosynthesis of some lysosomal glycoproteins. Results description: Whole-exome sequencing revealed a homozygous variant; 428G > A; p. (R143K) in SRD5A3 in one patient and a heterozygous one c.46G > A p. (Gly16Arg) in SLC35A2 in the other patient. Both variants were predicted to be likely pathogenic. Lysosome-associated membrane glycoprotein 2 (LAMP2) immunodetection in both cases showed a truncated form of the protein. Cystinosin (CTN) protein appeared as normal and truncated forms in both patients in ratios of the mature to truncated forms of CTN were lower than the control. The levels of the truncated forms of both cellular proteins were higher in the SRD5A3-CDG case compared to the SLC35A2-CDG case. The tetrameric form of cathepsin C (CTSC) was expressed at low levels in both cases with congenital disorder of glycosylation (CDG). SLC35A2-CDG patient had one extra-unknown band while SRD5A3-CDG patient had a missing band of CTSC forms. The expression patterns of lysosomal glycoproteins could be different between different types of CDG.

Thrombosis risk with estrogen use for puberty induction in congenital disorders of glycosylation.

Congenital disorders of glycosylation are a group of rare related disorders causing multisystem dysfunction, including ovarian failure in females that requires early estrogen replacement. Glycosylation defects also disrupt normal synthesis of several coagulation factors, increasing thrombotic risks and complicating hormone replacement. This series describes four females with different types of CDG who developed venous thromboses while on transdermal estrogen replacement. The authors highlight the knowledge gaps around anticoagulation for this population and propose further investigations.

Severe Ciliopathy-Like Phenotype in an Infant With a Novel MPDU1 Missense Variant.

Congenital disorders of glycosylation (CDG) are associated with ciliary dysfunction due to altered glycosylation of ciliary glycoproteins. We describe a severe ciliopathy-like phenotype in a female infant associated with a novel homozygous missense variant NM_004870.4(MPDU1):c.503G>A/p.Gly168Glu. Our findings, based on the co-segregation of the variant with the phenotype and in-silico analysis, implicate this MPDU1 missense variant in this disorder. Matched phenotype includes symmetric growth restriction, facial dysmorphism, ichthyosis, hepatomegaly with severe duct plate malformation, renal cortical tubular and glomerular cysts, moderate cerebral tetraventricular dilatation, and severe pontocerebellar hypoplasia. According to this observation, CDG should be included in the workup of infantile ciliopathy-like disorder.

Fractionated plasma N-glycan profiling of novel cohort of ATP6AP1-CDG subjects identifies phenotypic association.

ATP6AP1-CDG is an X-linked disorder typically characterized by hepatopathy, immunodeficiency, and an abnormal type II transferrin glycosylation pattern. Here, we present 11 new patients and clinical updates with biochemical characterization on one previously reported patient. We also document intrafamilial phenotypic variability and atypical presentations, expanding the symptomatology of ATP6AP1-CDG to include dystonia, hepatocellular carcinoma, and lysosomal abnormalities on hepatic histology. Three of our subjects received successful liver transplantation. We performed N-glycan profiling of total and fractionated plasma proteins for six patients and show associations with varying phenotypes, demonstrating potential diagnostic and prognostic value of fractionated N-glycan profiles. The aberrant N-linked glycosylation in purified transferrin and remaining plasma glycoprotein fractions normalized in one patient post hepatic transplant, while the increases of Man4GlcNAc2 and Man5GlcNAc2 in purified immunoglobulins persisted. Interestingly, in the single patient with isolated immune deficiency phenotype, elevated high-mannose glycans were detected on purified immunoglobulins without glycosylation abnormalities on transferrin or the remaining plasma glycoprotein fractions. Given the diverse and often tissue specific clinical presentations and the need of clinical management post hepatic transplant in ATP6AP1-CDG patients, these results demonstrate that fractionated plasma N-glycan profiling could be a valuable tool in diagnosis and disease monitoring.

Clinical and molecular findings in three Japanese patients with N-acetylneuraminic acid synthetase-congenital disorder of glycosylation (NANS-CDG).

We report clinical and molecular findings in three Japanese patients with N-acetylneuraminic acid synthetase-congenital disorder of glycosylation (NANS-CDG). Patient 1 exhibited a unique constellation of clinical features including marked hydrocephalus, spondyloepimetaphyseal dysplasia (SEMD), and thrombocytopenia which is comparable to that of an infant reported by Faye-Peterson et al., whereas patients 2 and 3 showed Camera-Genevieve type SMED with intellectual/developmental disability which is currently known as the sole disease name for NANS-CDG. Molecular studies revealed a maternally inherited likely pathogenic c.207del:p.(Arg69Serfs*57) variant and a paternally derived likely pathogenic c.979_981dup:p.(Ile327dup) variant in patient 1, a homozygous likely pathogenic c.979_981dup:p.(Ile327dup) variant caused by maternal segmental isodisomy involving NANS in patient 2, and a paternally inherited pathogenic c.133-12T>A variant leading to aberrant splicing and a maternally inherited likely pathogenic c.607T>C:p.(Tyr203His) variant in patient 3 (reference mRNA: NM_018946.4). The results, together with previously reported data, imply that (1) NANS plays an important role in postnatal growth and fetal brain development; (2) SMED is recognizable at birth and shows remarkable postnatal evolution; (3) NANS-CDG is associated with low-normal serum sialic acid, obviously elevated urine N-acetylmannosamine, and normal N- and O-glycosylation of serum proteins; and (4) NANS-CDG is divided into Camera-Genevieve type and more severe Faye-Peterson type.

[Analysis of SSR4 gene variant in a child with congenital glycosylation type 1y in conjunct with congenital dysplasia of external auditory canal].

OBJECTIVE: To explore the genetic basis for a child with congenital disorder of glycosylation type 1y (CDG-1y) in conjunct with congenital dysplasia of external auditory canal. METHODS: Trio-whole exome sequencing (trio-WES) was carried out for the family. Candidate variant was verified by Sanger sequencing. Pathogenicity of the variant was predicted with a variety of bioinformatic tools. RESULTS: The proband, a 10-years-old boy, presented with mental retardation, microcephaly and dysplasia of external auditory canal. Trio-WES revealed that he has harbored a de novo frameshift variant c.302dupC (p.Y102Lfs*2) in exon 4 of SSR4 gene, which was unreported previously (PS2). The variant was absent in major allele frequency databases (PM2) and was predicted to be pathogenic by multiple bioinformatic tools (PP3). UCSF chimera software suggested that the c.302dupC (p.Y102Lfs*2) variant can induce significant alteration to the structure of SSR4 protein, resulting loss of function (PVS1+PM1). Based on the guidelines from the American College of Medical Genetics and Genomics, the variant was classified as pathogenic (PVS1+PS2+PM1+PM2+PP3). CONCLUSION: The de novo frameshift variant c.302dupC (p.Y102Lfs*2) of the SSR4 gene probably underlay the child's condition. Above finding has enriched the spectrum of SSR4 mutations and the phenotypic spectrum of CDG-1y.

Expanding the phenotype of ATP6AP1 deficiency.

Vacuolar ATPases (V-ATPases) are large multisubunit proton pumps conserved among all eukaryotic cells that are involved in diverse functions including acidification of membrane-bound intracellular compartments. The ATP6AP1 gene encodes an accessory subunit of the vacuolar (V)-ATPase protein pump. Pathogenic variants in ATP6AP1 have been described in association with a congenital disorder of glycosylation (CDG), which are highly variable, but often characterized by immunodeficiency, hepatopathy, and neurologic manifestations. Although the most striking and common clinical feature is hepatopathy, the phenotypic and genotypic spectrum of ATP6AP1-CDG continues to expand. Here, we report identical twins who presented with acute liver failure and jaundice. Prenatal features included cystic hygroma, atrial septal defect, and ventriculomegaly. Postnatal features included pectus carinatum, connective tissue abnormalities, and hypospadias. Whole-exome sequencing (WES) revealed a novel de novo in-frame deletion in the ATP6AP1 gene (c.230_232delACT;p.Tyr77del). Although both twins have the commonly reported clinical feature of hepatopathy seen in other individuals with ATP6AP1-CDG-related disorder, they do not have neurological sequelae. This report expands the phenotypic spectrum of ATP6AP1-CDG-related disorder with both probands exhibiting unique prenatal and postnatal features, including fetal ventriculomegaly, umbilical hernia, pectus carinatum, micropenis, and hypospadias. Furthermore, this case affirms that neurological features described in the initial case series on ATP6AP1-CDG do not appear to be central, whereas the prenatal and connective tissue manifestations may be more common than previously thought. This emphasizes the importance of long-term clinical follow-up and variant interpretation using current updated recommendations.

Comprehensive Analysis of the Structure and Function of Peptide:N-Glycanase 1 and Relationship with Congenital Disorder of Deglycosylation.

The cytosolic PNGase (peptide:N-glycanase), also known as peptide-N4-(N-acetyl-ß-glucosaminyl)-asparagine amidase, is a well-conserved deglycosylation enzyme (EC 3.5.1.52) which catalyzes the non-lysosomal hydrolysis of an N(4)-(acetyl-ß-d-glucosaminyl) asparagine residue (Asn, N) into a N-acetyl-ß-d-glucosaminyl-amine and a peptide containing an aspartate residue (Asp, D). This enzyme (NGLY1) plays an essential role in the clearance of misfolded or unassembled glycoproteins through a process named ER-associated degradation (ERAD). Accumulating evidence also points out that NGLY1 deficiency can cause an autosomal recessive (AR) human genetic disorder associated with abnormal development and congenital disorder of deglycosylation. In addition, the loss of NGLY1 can affect multiple cellular pathways, including but not limited to NFE2L1 pathway, Creb1/Atf1-AQP pathway, BMP pathway, AMPK pathway, and SLC12A2 ion transporter, which might be the underlying reasons for a constellation of clinical phenotypes of NGLY1 deficiency. The current comprehensive review uncovers the NGLY1'ssdetailed structure and its important roles for participation in ERAD, involvement in CDDG and potential treatment for NGLY1 deficiency.

SLC10A7, an orphan member of the SLC10 family involved in congenital disorders of glycosylation.

SLC10A7, encoded by the so-called SLC10A7 gene, is the seventh member of a human sodium/bile acid cotransporter family, known as the SLC10 family. Despite similarities with the other members of the SLC10 family, SLC10A7 does not exhibit any transport activity for the typical SLC10 substrates and is then considered yet as an orphan carrier. Recently, SLC10A7 mutations have been identified as responsible for a new Congenital Disorder of Glycosylation (CDG). CDG are a family of rare and inherited metabolic disorders, where glycosylation abnormalities lead to multisystemic defects. SLC10A7-CDG patients presented skeletal dysplasia with multiple large joint dislocations, short stature and amelogenesis imperfecta likely mediated by glycosaminoglycan (GAG) defects. Although it has been demonstrated that the transporter and substrate specificities of SLC10A7, if any, differ from those of the main members of the protein family, SLC10A7 seems to play a role in Ca2+ regulation and is involved in proper glycosaminoglycan biosynthesis, especially heparan-sulfate, and N-glycosylation. This paper will review our current knowledge on the known and predicted structural and functional properties of this fascinating protein, and its link with the glycosylation process.

Impaired catabolism of free oligosaccharides due to MAN2C1 variants causes a neurodevelopmental disorder.

Free oligosaccharides (fOSs) are soluble oligosaccharide species generated during N-glycosylation of proteins. Although little is known about fOS metabolism, the recent identification of NGLY1 deficiency, a congenital disorder of deglycosylation (CDDG) caused by loss of function of an enzyme involved in fOS metabolism, has elicited increased interest in fOS processing. The catabolism of fOSs has been linked to the activity of a specific cytosolic mannosidase, MAN2C1, which cleaves α1,2-, α1,3-, and α1,6-mannose residues. In this study, we report the clinical, biochemical, and molecular features of six individuals, including two fetuses, with bi-allelic pathogenic variants in MAN2C1; the individuals are from four different families. These individuals exhibit dysmorphic facial features, congenital anomalies such as tongue hamartoma, variable degrees of intellectual disability, and brain anomalies including polymicrogyria, interhemispheric cysts, hypothalamic hamartoma, callosal anomalies, and hypoplasia of brainstem and cerebellar vermis. Complementation experiments with isogenic MAN2C1-KO HAP1 cells confirm the pathogenicity of three of the identified MAN2C1 variants. We further demonstrate that MAN2C1 variants lead to accumulation and delay in the processing of fOSs in proband-derived cells. These results emphasize the involvement of MAN2C1 in human neurodevelopmental disease and the importance of fOS catabolism.

SRD5A3-CDG: A Patient with a Novel Variant and Brain Neoplasm.

Congenital disorders of glycosylation (CDGs) are a large group of genetic diseases with impaired glycosylation of glycoproteins and glycolipids, and glycosylphosphatidylinositol anchor synthesis. Steroid 5α-reductase 3 (SRD5A3)-CDG is a CDG type I with a clinical spectrum of neurological, ophthalmological, dermatological and hepatic symptoms. Although CDGs are not directly related to malignancies, it is well known that some genes that are involved in glycosylation pathways are involved in various cancers. Aberrant glycosylation has been closely linked to the development and progression of brain cancer. We report a patient with SRD5A3-CDG carrying a novel homozygous splice variant and brain neoplasm. Also, a review of the literature is made regarding the multisystem effects of the disease. Key Words: SRD5A3-CDG, Glioma, Glycosylation, Transferrin isoelectric focusing, Congenital disorders of glycosylation.

Dissecting the transcriptional program of phosphomannomutase 2-deficient cells: Lymphoblastoide B cell lines as a valuable model for congenital disorders of glycosylation studies.

Congenital disorders of glycosylation (CDG) include 150 genetically and clinically heterogeneous diseases, showing significant glycoprotein hypoglycosylation that leads to pathological consequences in multiple organs and systems whose underlying mechanisms are not yet understood. A few cellular and animal models have been used to study specific CDG characteristics, although they have given limited information due to the few CDG mutations tested and the still missing comprehensive molecular and cellular basic research. Here, we provide specific gene expression profiles, based on ribonucleic acid (RNA) microarray analysis, together with some biochemical and cellular characteristics of a total of nine control Epstein-Barr virus-transformed lymphoblastoid B cell lines (B-LCL) and 13 CDG B-LCL from patients carrying severe mutations in the phosphomannomutase 2 (PMM2) gene, strong serum protein hypoglycosylation and neurological symptoms. Significantly dysregulated genes in PMM2-CDG cells included those regulating stress responses, transcription factors, glycosylation, motility, cell junction and, importantly, those related to development and neuronal differentiation and synapse, such as carbonic anhydrase 2 (CA2) and ADAM23. PMM2-CDG-associated biological consequences involved the unfolded protein response, RNA metabolism and the endoplasmic reticulum, Golgi apparatus and mitochondria components. Changes in the transcriptional and CA2 protein levels are consistent with the CDG physiopathology. These results demonstrate the global transcriptional impact in phosphomannomutase 2-deficient cells, reveal CA2 as a potential cellular biomarker and confirm B-LCL as an advantageous model for CDG studies.

Patient-derived gene and protein expression signatures of NGLY1 deficiency.

N-Glycanase 1 (NGLY1) deficiency is a rare and complex genetic disorder. Although recent studies have shed light on the molecular underpinnings of NGLY1 deficiency, a systematic characterization of gene and protein expression changes in patient-derived cells has been lacking. Here, we performed RNA-sequencing and mass spectrometry to determine the transcriptomes and proteomes of 66 cell lines representing four different cell types derived from 14 NGLY1 deficient patients and 17 controls. Although NGLY1 protein levels were up to 9.5-fold downregulated in patients compared with parents, residual and likely non-functional NGLY1 protein was detectable in all patient-derived lymphoblastoid cell lines. Consistent with the role of NGLY1 as a regulator of the transcription factor Nrf1, we observed a cell type-independent downregulation of proteasomal genes in NGLY1 deficient cells. In contrast, genes involved in ribosome biogenesis and mRNA processing were upregulated in multiple cell types. In addition, we observed cell type-specific effects. For example, genes and proteins involved in glutathione synthesis, such as the glutamate-cysteine ligase subunits GCLC and GCLM, were downregulated specifically in lymphoblastoid cells. We provide a web application that enables access to all results generated in this study at https://apps.embl.de/ngly1browser. This resource will guide future studies of NGLY1 deficiency in directions that are most relevant to patients.

Assay for the peptide:N-glycanase/NGLY1 and disease-specific biomarkers for diagnosing NGLY1 deficiency.

Cytosolic peptide:N-glycanase (NGLY1 in mammals), a highly conserved enzyme in eukaryotes, catalyses the deglycosylation of N-glycans that are attached to glycopeptide/glycoproteins. In 2012, an autosomal recessive disorder related to the NGLY1 gene, which was referred to as NGLY1 deficiency, was reported. Since then, more than 100 patients have been identified. Patients with this disease exhibit various symptoms, including various motor deficits and other neurological problems. Effective therapeutic treatments for this disease, however, have not been established. Most recently, it was demonstrated that the intracerebroventricular administration of an adeno-associated virus 9 vector expressing human NGLY1 during the weaning period allowed some motor functions to be recovered in Ngly1-/- rats. This observation led us to hypothesize that a therapeutic intervention for improving these motor deficits or other neurological symptoms found in the patients might be possible. To achieve this, it is critical to establish robust and facile methods for assaying NGLY1 activity in biological samples, for the early diagnosis and evaluation of the therapeutic efficacy for the treatment of NGLY1 deficiency. In this mini review, we summarize progress made in the development of various assay methods for NGLY1 activity, as well as a recent progress in the identification of NGLY1 deficiency-specific biomarkers.

[Analysis of SLC35A2 gene variant in a child with congenital disorder of glycosylation type IIm].

OBJECTIVE: To investigate the clinical features and SLC35A2 variant of a case of congenital disorder of glycosylation type IIm (CDG-IIm), and to identify the possible causes of the disease. METHODS: Trio-whole exome sequencing (WES) was used to analyze the gene variant of the children and their parents. The suspicious gene variants were screened for Sanger verification and the bioinformatics prediction was used to analyze the hazard of variant. RESULTS: The clinical manifestations of the child were epilepsy, global growth retardation, nystagmus, myocarditis and other symptoms. MRI showed brain dysplasia such as wide frontal temporal sulcus and subarachnoid space on both sides. Echocardiography showed left ventricular wall thickening and patent foramen ovale. According to the results of gene detection, there was a heterozygous missense variant c.335C>A (p.Thr112Lys) in SLC35A2 gene. The parents were wild-type at this locus, which was a de novo variant. At the same time, there was no report of this variant in the relevant literature, which was a novel variant in SLC35A2 gene. According to the genetic variant guidelines of American College of Medical Genetics and Genomics, SLC35A2 gene c.335C>A (p.Thr112Lys) variant was predicted to be likely pathogenic (PS2+PM2+PP3). CONCLUSION: The variant of SLC35A2 gene c.335C>A(p.Thr112Lys) may be the cause of the disease in the child.

Transferrin gene polymorphisms alter the transferrin focusing pattern, making congenital disorder of glycosylation diagnosis difficult.

BACKGROUND: Several transferrin gene polymorphisms are known to result in a shifted IEF pattern. The aim of this study was to characterize the transferrin gene polymorphisms observed in patients from one referral center. MATERIALS AND METHODS: Patients with solely increased pentasialo-Tf were selected. The whole exome sequencing was done from probands (patients) and from DNA available from their parents. RESULTS: Two various polymorphisms in the transferrin gene: c.2012G>A, p.Gly671Glu and c.1027C>T, p.Arg343Trp, were found. CONCLUSIONS: Two transferrin gene polymorphisms: c.2012G>A, p.(Gly671Glu) and c.1027C>T, p.(Arg343Trp) solely correspond to an elevated pentasialo-Tf.

Congenital disorders of glycosylation - an umbrella term for rapidly expanding group of rare genetic metabolic disorders - importance of physical investigation.

AIM: Congenital disorders of glycosylation (CDG) belong to an expanding group of rare genetic metabolic disorders caused by defects in the complex chemical enzymatic process of glycosylation. The study is aimed at presenting a case report of a premature dysmorphic newborn, clinical presentation of the condition, the way it was diagnosed and treated, as well as its comparison with the known cases. RESULTS: The result of glycan analysis supports the assumption of a supposed glycosylation disorder and also specifies a specific subtype: CDG-1, subtype ALG12-CDG (Ig). CONCLUSION: CDG have an extremely wide clinical spectrum and should be considered in any child with unexplained developmental delay, failure to thrive, seizures, and abnormalities in liver enzymes, coagulation and immunologic factors. The treatment of most forms of CDG depends upon numerous factors such as specific symptoms present, severity of the disorder, age and overall health of the patients and tolerance to certain medications or procedures. For these reasons, the treatment is specific for every individual. It is based on the symptoms and requires a coordination of efforts of a team of specialists (Tab. 4, Fig. 3, Ref. 19).

NGLY1 deficiency: Novel variants and literature review.

NGLY1 deficiency is a recently described autosomal recessive disorder, involved in deglycosylation of proteins, and for that reason grouped as the congenital disorders of deglycosylation together with the lysosomal storage disorders. The typical phenotype is characterized by intellectual disability, liver malfunctioning, muscular hypotonia, involuntary movements, and decreased or absent tear production. Liver biopsy demonstrates vacuolar amorphous cytoplasmic storage material. NGLY1 deficiency is caused by bi-allelic variants in NGLY1 which catalyzes protein deglycosylation. We describe five patients from two families with NGLY1 deficiency due to homozygosity for two novel NGLY1 variants, and compare their findings to those of earlier reported patients. The typical features of the disorder are present in a limited way, and there is intra-familial variability. In addition in one of the families the muscle atrophy and posture abnormalities are marked. These can be explained either as variability of the phenotype or as sign of slowly progression of features as the present affected individuals are older than earlier reported patients.

Liver manifestations in a cohort of 39 patients with congenital disorders of glycosylation: pin-pointing the characteristics of liver injury and proposing recommendations for follow-up.

BACKGROUND: The congenital disorders of glycosylation (CDG) are a heterogeneous group of rare metabolic diseases with multi-system involvement. The liver phenotype of CDG varies not only according to the specific disorder, but also from patient to patient. In this study, we sought to identify common patterns of liver injury among patients with a broad spectrum of CDG, and to provide recommendations for follow-up in clinical practice. METHODS: Patients were enrolled in the Frontiers in Congenital Disorders of Glycosylation natural history study. We analyzed clinical history, molecular genetics, serum markers of liver injury, liver ultrasonography and transient elastography, liver histopathology (when available), and clinical scores of 39 patients with 16 different CDG types (PMM2-CDG, n = 19), with a median age of 7 years (range: 10 months to 65 years). For patients with disorders which are treatable by specific interventions, we have added a description of liver parameters on treatment. RESULTS: Our principal findings are (1) there is a clear pattern in the evolution of the hepatocellular injury markers alanine aminotransferase and aspartate aminotransferase according to age, especially in PMM2-CDG patients but also in other CDG-I, and that the cholangiocellular injury marker gamma-glutamyltransferase is not elevated in most patients, pointing to an exclusive hepatocellular origin of injury; (2) there is a dissociation between liver ultrasound and transient elastography regarding signs of liver fibrosis; (3) histopathological findings in liver tissue of PMM2-CDG patients include cytoplasmic glycogen deposits; and (4) most CDG types show more than one type of liver injury. CONCLUSIONS: Based on these findings, we recommend that all CDG patients have regular systematic, comprehensive screening for liver disease, including physical examination (for hepatomegaly and signs of liver failure), laboratory tests (serum alanine aminotransferase and aspartate aminotransferase), liver ultrasound (for steatosis and liver tumors), and liver elastography (for fibrosis).