PGM3 mutations cause a congenital disorder of glycosylation with severe immunodeficiency and skeletal dysplasia

Treatment of congenital disorders of glycosylation: An overview

While the identification and diagnosis of congenital disorders of glycosylation (CDG) have rapidly progressed, the available treatment options are still quite limited. Mostly, we are only able to manage the disease symptoms rather than to address the underlying cause. However, recent years have brought about remarkable advances in treatment approaches for some CDG. Innovative therapies, targeting both the root cause and resulting manifestations, have transitioned from the research stage to practical application. The present paper aims to provide a detailed overview of these exciting developments and the rising concepts that are used to treat these ultra-rare diseases.

Functional overlap of inborn errors of immunity and metabolism genes defines T cell metabolic vulnerabilities

Inborn errors of metabolism (IEMs) and immunity (IEIs) are Mendelian diseases in which complex phenotypes and patient rarity have limited clinical understanding. Whereas few genes have been annotated as contributing to both IEMs and IEIs, immunometabolic demands suggested greater functional overlap. Here, CRISPR screens tested IEM genes for immunologic roles and IEI genes for metabolic effects and found considerable previously unappreciated crossover. Analysis of IEMs showed that N-linked glycosylation and the hexosamine pathway enzyme Gfpt1 are critical for T cell expansion and function. Further, T helper (TH1) cells synthesized uridine diphosphate N-acetylglucosamine more rapidly and were more impaired by Gfpt1 deficiency than TH17 cells. Screening IEI genes found that Bcl11b promotes the CD4 T cell mitochondrial activity and Mcl1 expression necessary to prevent metabolic stress. Thus, a high degree of functional overlap exists between IEM and IEI genes, and immunometabolic mechanisms may underlie a previously underappreciated intersection of these disorders.

Genetic Evaluation of the Patients with Clinically Diagnosed Inborn Errors of Immunity by Whole Exome Sequencing: Results from a Specialized Research Center for Immunodeficiency in Türkiye

Molecular diagnosis of inborn errors of immunity (IEI) plays a critical role in determining patients' long-term prognosis, treatment options, and genetic counseling. Over the past decade, the broader utilization of next-generation sequencing (NGS) techniques in both research and clinical settings has facilitated the evaluation of a significant proportion of patients for gene variants associated with IEI. In addition to its role in diagnosing known gene defects, the application of high-throughput techniques such as targeted, exome, and genome sequencing has led to the identification of novel disease-causing genes. However, the results obtained from these different methods can vary depending on disease phenotypes or patient characteristics. In this study, we conducted whole-exome sequencing (WES) in a sizable cohort of IEI patients, consisting of 303 individuals from 21 different clinical immunology centers in Türkiye. Our analysis resulted in likely genetic diagnoses for 41.1% of the patients (122 out of 297), revealing 52 novel variants and uncovering potential new IEI genes in six patients. The significance of understanding outcomes across various IEI cohorts cannot be overstated, and we believe that our findings will make a valuable contribution to the existing literature and foster collaborative research between clinicians and basic science researchers.

Evidence of synergistic mechanisms of hepatoprotective botanical herbal preparation of Pueraria montana var. lobata and Schisandra sphenanthera

Background

Pueraria montana var. lobata (Willd.) Maesen & S.M.Almeida ex Sanjappa & Predeep (syn. Pueraria lobata (Willd.) Ohwi) and Schisandra sphenanthera Rehder & E.H. Wilson are traditional edible and medicinal hepatoprotective botanical drugs. Studies have shown that the combination of two botanical drugs enhanced the effects of treating acute liver injury (ALI), but the synergistic effect and its action mechanisms remain unclear. This study aimed to investigate the synergistic effect and its mechanism of the combination of Pueraria montana var. lobata (Willd.) Maesen & S.M.Almeida ex Sanjappa & Predeep (syn. Pueraria lobata (Willd.) Ohwi) (PM) and Schisandra sphenanthera Rehder & E.H. Wilson (SS) in the treatment of ALI.

Methods

High performance liquid chromatography (HPLC) were utilized to conduct the chemical interaction analysis. Then the synergistic effects of botanical hybrid preparation of PM-SS (BHP PM-SS) against ALI were comprehensively evaluated by the CCl4 induced ALI mice model. Afterwards, symptom-oriented network pharmacology, transcriptomics and metabolomics were applied to reveal the underlying mechanism of action. Finally, the key target genes were experimentally by RT-qPCR.

Results

Chemical analysis and pharmacodynamic experiments revealed that BHP PM-SS was superior to the single botanical drug, especially at 2:3 ratio, with a better dissolution rate of active ingredients and synergistic anti-ALI effect. Integrated symptom-oriented network pharmacology combined with transcriptomics and metabolomics analyses showed that the active ingredients of BHP PM-SS could regulate Glutathione metabolism, Pyrimidine metabolism, Arginine biosynthesis and Amino acid sugar and nucleotide sugar metabolism, by acting on the targets of AKT1, TNF, EGFR, JUN, HSP90AA1 and STAT3, which could be responsible for the PI3K-AKT signaling pathway, MAPK signaling pathway and Pathway in cancer to against ALI.

Conclusion

Our study has provided compelling evidence for the synergistic effect and its mechanism of the combination of BHP PM-SS, and has contributed to the development and utilization of BHP PM-SS dietary supplements.

Genomic insights into inherited bone marrow failure syndromes in a Korean population

Inherited bone marrow failure syndromes (IBMFS) pose significant diagnostic challenges due to overlapping symptoms and variable expressivity, despite evolving genomic insights. The study aimed to elucidate the genomic landscape among 130 Korean patients with IBMFS. We conducted targeted next-generation sequencing (NGS) and clinical exome sequencing (CES) across the cohort, complemented by whole genome sequencing (WGS) and chromosomal microarray (CMA) in 12 and 47 cases, respectively, with negative initial results. Notably, 50% (n = 65) of our cohort achieved a genomic diagnosis. Among these, 35 patients exhibited mutations associated with classic IBMFSs (n = 33) and the recently defined IBMFS, aplastic anaemia, mental retardation and dwarfism syndrome (AmeDS, n = 2). Classic IBMFSs were predominantly detected via targeted NGS (85%, n = 28) and CES (88%, n = 29), whereas AMeDS was exclusively identified through CES. Both CMA and WGS aided in identifying copy number variations (n = 2) and mutations in previously unexplored regions (n = 2). Additionally, 30 patients were diagnosed with other congenital diseases, encompassing 13 distinct entities including inherited thrombocytopenia (n = 12), myeloid neoplasms with germline predisposition (n = 8), congenital immune disorders (n = 7) and miscellaneous genomic conditions (n = 3). CES was particularly effective in revealing these diverse diagnoses. Our findings underscore the significance of comprehensive genomic analysis in IBMFS, highlighting the need for ongoing exploration in this complex field.

Revisiting the immunopathology of congenital disorders of glycosylation: an updated review

Glycosylation is a critical post-translational modification that plays a pivotal role in several biological processes, such as the immune response. Alterations in glycosylation can modulate the course of various pathologies, such as the case of congenital disorders of glycosylation (CDG), a group of more than 160 rare and complex genetic diseases. Although the link between glycosylation and immune dysfunction has already been recognized, the immune involvement in most CDG remains largely unexplored and poorly understood. In this study, we provide an update on the immune dysfunction and clinical manifestations of the 12 CDG with major immune involvement, organized into 6 categories of inborn errors of immunity according to the International Union of Immunological Societies (IUIS). The immune involvement in phosphomannomutase 2 (PMM2)-CDG - the most frequent CDG - was comprehensively reviewed, highlighting a higher prevalence of immune issues during infancy and childhood and in R141H-bearing genotypes. Finally, using PMM2-CDG as a model, we point to links between abnormal glycosylation patterns in host cells and possibly favored interactions with microorganisms that may explain the higher susceptibility to infection. Further characterizing immunopathology and unusual host-pathogen adhesion in CDG can not only improve immunological standards of care but also pave the way for innovative preventive measures and targeted glycan-based therapies that may improve quality of life for people living with CDG.

The role of glycosylation in clinical allergy and immunology

While glycans are among the most abundant macromolecules on the cell with widespread functions, their role in immunity has historically been challenging to study. This is in part due to difficulties assimilating glycan analysis into routine approaches used to interrogate immune cell function. Despite this, recent developments have illuminated fundamental roles for glycans in host immunity. The growing field of glycoimmunology continues to leverage new tools and approaches to uncover the function of glycans and glycan-binding proteins in immunity. Here we utilize clinical vignettes to examine key roles of glycosylation in allergy, inborn errors of immunity, and autoimmunity. We will discuss the diverse functions of glycans as epitopes, as modulators of antibody function, and as regulators of immune cell function. Finally, we will highlight immune modulatory therapies that harness the critical role of glycans in the immune system.

Genetic Characteristics of Patients with Young-Onset Myelodysplastic Neoplasms

Myelodysplastic neoplasm (MDS) is a heterogeneous group of myeloid neoplasms affected by germline and somatic genetic alterations. The incidence of MDS increases with age but rarely occurs at a young age. We investigated the germline and somatic genetic alterations of Korean patients with young-onset MDS (<40 years). Among the thirty-one patients, five (16.1%) had causative germline variants predisposing them to myeloid neoplasms (three with GATA2 variants and one each with PGM3 and ETV variants). We found that PGM3 deficiency, a subtype of severe immunodeficiency, predisposes patients to MDS. Somatic mutations were identified in 14 patients (45.2%), with lower rates in patients aged < 20 years (11.1%). Nine (29%) patients had U2AF1 S34F/Y mutations, and patients with U2AF1 mutations showed significantly worse progression-free survival (p < 0.001) and overall survival (p = 0.006) than those without U2AF1 mutations. A UBA1 M41T mutation that causes VEXAS syndrome was identified in a male patient. In conclusion, a germline predisposition to myeloid neoplasms occurred in ~16% of young-onset MDS patients and was largely associated with primary immunodeficiencies, including GATA2 deficiency. Furthermore, the high frequency of somatic U2AF1 mutations in patients with young-onset MDS suggests the presence of a distinct MDS subtype.

Clinical and biochemical footprints of inherited metabolic disease. XVI. Hematological abnormalities

Many classical inherited metabolic diseases (IMDs) are associated with significant hematological complications such as anemia or thrombosis. While these may not be the prominent presenting feature of these conditions, management of these issues is important for optimal outcomes in people with IMDs. Some disorders that are included in the nosology of inherited metabolic disorders, such as inherited disorders of red cell energy metabolism, have purely hematological features, and have typically been cared for by a hematologist. In the 16th issue of the Footprints series, we identified 265 IMDs associated with hematological abnormalities. We review the major hematological manifestations of IMDs, suggest further investigation of hematological findings, and discuss treatment options available for specific hematological complications of IMDs.

Next generation sequencing (NGS)-based approach to diagnosing Algerian patients with suspected inborn errors of immunity (IEIs)

The advent of next-generation sequencing (NGS) technologies has greatly expanded our understanding of both the clinical spectra and genetic landscape of inborn errors of immunity (IEIs). Endogamous populations may be enriched for unique, ancestry-specific disease-causing variants, a consideration that significantly impacts molecular testing and analysis strategies. Herein, we report on the application of a 2-step NGS-based testing approach beginning with targeted gene panels (TGPs) tailored to specific IEI subtypes and reflexing to whole exome sequencing (WES) if negative for Northwest Algerian patients with suspected IEIs. Our overall diagnostic yield of 57% is comparable to others broadly applying short-read NGS to IEI detection, but data from our localized cohort show some similarities and differences from NGS studies performed on larger regional IEI cohorts. This suggests the importance of tailoring diagnostic strategies to local demographics and needs, but also highlights ongoing concerns inherent to the application of genomics for clinical IEI diagnostics.

The Reciprocal Interplay between Infections and Inherited Metabolic Disorders

Infections represent the main cause of acute metabolic derangements and/or the worsening of the clinical course of many inherited metabolic disorders (IMDs). The basic molecular mechanisms behind the role of infections in these conditions have not been completely clarified. This review points out the different mechanisms behind the relationship between IMDs and infections, providing an overview of this still-under-investigated area. Classically, infections have been considered as the consequence of a compromised immune system due to a biochemical defect of energy production. An adjunctive pathogenetic mechanism is related to a genetically altered protein-attached glycans composition, due to congenital glycosilation defects. In addition, a dietary regimen with a reduced intake of both micro- and macronutrients can potentially compromise the ability of the immune system to deal with an infection. There is recent pre-clinical evidence showing that during infections there may be a disruption of substrates of various metabolic pathways, leading to further cellular metabolic alteration. Therefore, infective agents may affect cellular metabolic pathways, by mediation or not of an altered immune system. The data reviewed here strongly suggest that the role of infections in many types of IMDs deserves greater attention for a better management of these disorders and a more focused therapeutic approach.

ERBIN and phosphoglucomutase 3 deficiency

ERBIN and phosphoglucomutase 3 (PGM3) mutations both lead to rare primary atopic disorders characterized by allergic disease and connective tissue abnormalities, though each disorder has its own rather unique pattern of multisystem presentations. Pathway studies show how ERBIN mutations allow for enhanced TGFb signaling, and prevent STAT3 from negative-regulating TGFb signaling. This likely explains many elements of clinical overlap between disorders of STAT3 and TGFb signaling. The excessive TGFb signaling leading to increased IL-4 receptor expression also provides the rationale for precision-based therapy blocking the IL-4 receptor to treat the atopic disease. The mechanism by which PGM3 deficiency leads to atopic phenotypes is not well understood, nor is the broad variability in disease penetrance and expressivity, though preliminary studies suggest an overlap with IL-6 receptor signaling defects.

Hyper IgE syndrome-related disease treated with dupilumab: A case report

Phosphoglucomutase 3 (PGM3) catalyzes the glycosylation of immune system precursor proteins. Its impairment leads to severe infections and other developmental, musculoskeletal, and nervous system defects. We present a case of a 2-month-old female patient with recurrent infections and diffuse eczematous dermatitis recalcitrant to corticosteroids. A next-generation sequencing NGS gene panel for inherited immune dysfunction syndromes revealed multiple variants of unknown significance in key immune regulators, specifically heterozygous mutation c.337C⟩G (p.Pro113Ala) on exon 4 of PGM3 as a novel variant in the PGM3 associated diseases. Off-label use of dupilumab resulted in rapid improvement.

Congenital disorders of glycosylation: narration of a story through its patents

Congenital disorders of glycosylation are a group of more than 160 rare genetic defects in protein and lipid glycosylation. Since the first clinical report in 1980 of PMM2-CDG, the most common CDG worldwide, research made great strides, but nearly all of them are still missing a cure. CDG diagnosis has been at a rapid pace since the introduction of whole-exome/whole-genome sequencing as a diagnostic tool. Here, we retrace the history of CDG by analyzing all the patents associated with the topic. To this end, we explored the Espacenet database, extracted a list of patents, and then divided them into three major groups: (1) Drugs/therapeutic approaches for CDG, (2) Drug delivery tools for CDG, (3) Diagnostic tools for CDG. Despite the enormous scientific progress experienced in the last 30 years, diagnostic tools, drugs, and biomarkers are still urgently needed.

High serum mannose in colorectal cancer: a novel biomarker of lymph node metastasis and poor prognosis

Background

Lymph node status is an important prognostic indicator and it significantly influences treatment decisions for colorectal cancer (CRC). The objective of this study was to evaluate the ability of serum monosaccharides in predicting lymph node metastasis (LNM) and prognosis.

Methods

High performance anion exchange chromatography coupled with pulsed amperometric detector (HPAEC-PAD) was used to quantify serum monosaccharides from 252 CRC patients. Receiver operating characteristic (ROC) curves were used to evaluate predictive performance of parameters. Predictors of LNM were evaluated by univariate and multivariate analyses. The prognostic role of the factors was evaluated by survival analysis.

Results

The levels of serum mannose (Man) and galactose (Gal) were significantly increased in patients with LNM (p <0.0001, p =0.0017, respectively). The area under the curves (AUCs) of Man was 0.8140, which was higher than carcinoembryonic antigen (CEA) (AUC =0.6523). Univariate and multivariate analyses demonstrated histologic grade (G3) (odds ratio [OR] =2.60, p =0.043), histologic grade (mucin-producing subtype) (odds ratio [OR] =3.38, p =0.032), lymphovascular invasion (LVI) (OR =2.42, p <0.01), CEA (>5ng/ml) (OR =1.85, p =0.042) and high Man (OR =2.65, p =0.006) to be independent risk factors of LNM. The survival analysis showed that the high serum Man was independent risk factor for poor prognosis in CRC patients (HR=1.75, p =0.004).

Conclusions

The Man is superior to CEA in prediction of LNM for CRC patients. Man is expected to be a predictor for LNM in CRC. High serum Man is associated with poor prognosis of CRC patients.

Glycome dynamics in T and B cell development: basic immunological mechanisms and clinical applications

Glycans cover the surfaces of all mammalian cells through a process called glycosylation. Nearly all proteins and receptors that integrate the intricate series of co-stimulatory/inhibitory pathways of the immune system are glycosylated. Growing evidence indicates that the development of the immune system at the origins of T and B cell development is tightly regulated by glycosylation. In this opinion, we hypothesize that the glycome composition of developing T and B cells is developmentally regulated. We discuss how glycans play fundamental roles in lymphocyte development and how glycans early define T and B cell functionality in multiple aspects of adaptive immunity. These advances can provide opportunities for the discovery of novel disease factors and more effective candidate treatments for various conditions.

Clinical and biochemical footprints of inherited metabolic diseases. XII. Immunological defects

Immunological problems are increasingly acknowledged manifestations in many inherited metabolic diseases (IMDs), ranging from exaggerated inflammation, autoimmunity and abnormal cell counts to recurrent microbial infections. A subgroup of IMDs, the congenital disorders of glycosylation (CDG), includes CDG types that are even classified as primary immunodeficiencies. Here, we reviewed the list of metabolic disorders reported to be associated with various immunological defects and identified 171 IMDs accompanied by immunological manifestations. Most IMDs are accompanied by immune dysfunctions of which immunodeficiency and infections, innate immune defects, and autoimmunity are the most common abnormalities reported in 144/171 (84%), 44/171 (26%) and 33/171 (19%) of IMDs with immune system involvement, respectively, followed by autoinflammation 17/171 (10%). This article belongs to a series aiming at creating and maintaining a comprehensive list of clinical and metabolic differential diagnoses according to organ system involvement.

The Hexosamine Biosynthesis Pathway: Regulation and Function

The hexosamine biosynthesis pathway (HBP) produces uridine diphosphate-N-acetyl glucosamine, UDP-GlcNAc, which is a key metabolite that is used for N- or O-linked glycosylation, a co- or post-translational modification, respectively, that modulates protein activity and expression. The production of hexosamines can occur via de novo or salvage mechanisms that are catalyzed by metabolic enzymes. Nutrients including glutamine, glucose, acetyl-CoA, and UTP are utilized by the HBP. Together with availability of these nutrients, signaling molecules that respond to environmental signals, such as mTOR, AMPK, and stress-regulated transcription factors, modulate the HBP. This review discusses the regulation of GFAT, the key enzyme of the de novo HBP, as well as other metabolic enzymes that catalyze the reactions to produce UDP-GlcNAc. We also examine the contribution of the salvage mechanisms in the HBP and how dietary supplementation of the salvage metabolites glucosamine and N-acetylglucosamine could reprogram metabolism and have therapeutic potential. We elaborate on how UDP-GlcNAc is utilized for N-glycosylation of membrane and secretory proteins and how the HBP is reprogrammed during nutrient fluctuations to maintain proteostasis. We also consider how O-GlcNAcylation is coupled to nutrient availability and how this modification modulates cell signaling. We summarize how deregulation of protein N-glycosylation and O-GlcNAcylation can lead to diseases including cancer, diabetes, immunodeficiencies, and congenital disorders of glycosylation. We review the current pharmacological strategies to inhibit GFAT and other enzymes involved in the HBP or glycosylation and how engineered prodrugs could have better therapeutic efficacy for the treatment of diseases related to HBP deregulation.

Functional Overlap of Inborn Errors of Immunity and Metabolism Genes Define T Cell Immunometabolic Vulnerabilities

Inborn Errors of Metabolism (IEM) and Immunity (IEI) are Mendelian diseases in which complex phenotypes and patient rarity can limit clinical annotations. Few genes are assigned to both IEM and IEI, but immunometabolic demands suggest functional overlap is underestimated. We applied CRISPR screens to test IEM genes for immunologic roles and IEI genes for metabolic effects and found considerable crossover. Analysis of IEM showed N-linked glycosylation and the de novo hexosamine synthesis enzyme, Gfpt1 , are critical for T cell expansion and function. Interestingly, Gfpt1 -deficient T H 1 cells were more affected than T H 17 cells, which had increased Nagk for salvage UDP-GlcNAc synthesis. Screening IEI genes showed the transcription factor Bcl11b promotes CD4 + T cell mitochondrial activity and Mcl1 expression necessary to prevent metabolic stress. These data illustrate a high degree of functional overlap of IEM and IEI genes and point to potential immunometabolic mechanisms for a previously unappreciated set of these disorders.

HIGHLIGHTS

Inborn errors of immunity and metabolism have greater overlap than previously known Gfpt1 deficiency causes an IEM but also selectively regulates T cell subset fate Loss of Bcl11b causes a T cell deficiency IEI but also harms mitochondrial function Many IEM may have immune defects and IEI may be driven by metabolic mechanisms.

Tailored treatments in inborn errors of immunity associated with atopy (IEIs-A) with skin involvement

Inborn errors of immunity associated with atopy (IEIs-A) are a group of inherited monogenic disorders that occur with immune dysregulation and frequent skin involvement. Several pathways are involved in the pathogenesis of these conditions, including immune system defects, alterations of skin barrier and metabolism perturbations. Current technological improvements and the higher accessibility to genetic testing, recently allowed the identification of novel molecular pathways involved in IEIs-A, also informing on potential tailored therapeutic strategies. Compared to other systemic therapy for skin diseases, biologics have the less toxic and the best tolerated profile in the setting of immune dysregulation. Here, we review IEIs-A with skin involvement focusing on the tailored therapeutic approach according to their pathogenetic mechanism.

Novel PGM3 mutation in two siblings with combined immunodeficiency and childhood bullous pemphigoid: a case report and review of the literature

BACKGROUND

Bullous pemphigoid is the most common autoimmune subepidermal blistering disorder with a low incidence in childhood. Combined immunodeficiencies (CIDs) are a group of monogenic inborn errors of immunity (IEIs) characterized by T- and B-cell dysfunction leading to recurrent infections, lymphoproliferation, predisposition to malignancy, and autoimmunity. Here, we report two Afghan siblings with a diagnosis of CID and extremely rare manifestation of diffuse bullous pemphigoid skin lesions.

CASE PRESENTATION

The older sibling (patient 1) was a 32-month-old male with facial dysmorphism, protracted diarrhea, failure to thrive, recurrent oral candidiasis, recurrent otitis media with tympanic membrane perforation, who had been previously diagnosed with CID. While he was under treatment with intravenous immunoglobulin (IVIg), he developed extensive blistering lesions, which were diagnosed as childhood bullous pemphigoid. Methylprednisolone and azathioprine were added to the regimen, which resulted in a remarkable improvement of the skin lesions and also the feeding condition. However,2 weeks later, he was re-admitted to the intensive care unit (ICU) and eventually died due to fulminant sepsis. Later, his 12-month-old sister (patient 2) with similar facial dysmorphism and a history of developmental delay, food allergy, recurrent oral candidiasis, and respiratory tract infections also developed blistering skin lesions. She was under treatment for occasional eczematous lesions, and had been receiving IVIg for 3 months due to low levels of immunoglobulins. Further immunologic workup showed an underlying CID and thus treatment with IVIg continued, gradually improving her clinical condition. The genetic study of both siblings revealed a novel homozygous mutation in exon 7 of the PGM3 gene, c.845 T > C (p.Val282Ala).

CONCLUSIONS

Dermatologic disorders may be the presenting sign in patients with CID and mutated PGM3. This case report further extends the spectrum of skin manifestations that could be observed in PGM3 deficiency and emphasizes the importance of considering CIDs during the assessment of skin disorders, particularly if they are extensive, recurrent, refractory to treatment, and/or associated with other signs of IEIs.

Genetic/Environmental Contributions and Immune Dysregulation in Children with Atopic Dermatitis

Atopic dermatitis (AD) is one of the most common skin conditions in humans. AD affects up to 20% of children worldwide and results in morbidity for both patients and their caregivers. The basis of AD is an interplay between genetics and the environment characterized by immune dysregulation. A myriad of mutations that compromise the skin barrier and/or immune function have been linked to AD. Of these, filaggrin gene (FLG) mutations are the most evidenced. Many other mutations have been implicated in isolated studies that are often unreplicated, creating an archive of genes with potential but unconfirmed relevance to AD. Harnessing big data, polygenic risk scores (PRSs) and genome-wide association studies (GWAS) may provide a more practical strategy for identifying the genetic signatures of AD. Epigenetics may also play a role. Staphylococcus aureus is the most evidenced microbial contributor to AD. Cutaneous dysbiosis may result in over-colonization by pathogenic strains and aberrant skin immunity and inflammation. Aeroallergens, air pollution, and climate are other key environmental contributors to AD. The right climate and/or commensals may improve AD for some patients.

A novel variant in GNPNAT1 gene causing a spondylo-epi-metaphyseal dysplasia resembling PGM3-Desbuquois like dysplasia

Spondylo-epi-metaphyseal dysplasias (SEMDs) are a clinically and genetically heterogeneous group of skeletal dysplasias characterized by short stature and abnormal modeling of the spine and long bones. A novel form of rhizomelic skeletal dysplasia, Ain-Naz type, associated with a homozygous variant in GNPNAT1 was recently identified. Herein, we report an Egyptian patient, offspring of consanguineous parents, who presented with a severe form of unclassified SEMD. Whole exome sequencing identified a novel homozygous variant in exon 3, c.77T>G, (p.Phe26Cys) in GNPNAT1, that was confirmed by Sanger sequencing and both parents were found to be heterozygous for the identified variant. Main features included severe short stature, rhizomelic limb shortening, and wide flared metaphysis. Short broad long bones, brachydactyly, delayed epiphyseal ossification of long bones, advanced bone age, and immunodeficiency were additional findings expanding the clinical phenotype described in the previously reported family. We conclude that variants in the GNPNAT1 gene cause an autosomal recessive form of SEMD resembling Desbuquois like dysplasia caused by PGM3, which is involved in the same pathway as GNPNAT1.

Atopic Dermatitis-like Genodermatosis: Disease Diagnosis and Management

Eczema is a classical characteristic not only in atopic dermatitis but also in various genodermatosis. Patients suffering from primary immunodeficiency diseases such as hyper-immunoglobulin E syndromes, Wiskott-Aldrich syndrome, immune dysregulation, polyendocrinopathy, enteropathy, X-linked syndrome, STAT5B deficiency, Omenn syndrome, atypical complete DiGeorge syndrome; metabolic disorders such as acrodermatitis enteropathy, multiple carboxylase deficiency, prolidase deficiency; and other rare syndromes like severe dermatitis, multiple allergies and metabolic wasting syndrome, Netherton syndrome, and peeling skin syndrome frequently perform with eczema-like lesions. These genodermatosis may be misguided in the context of eczematous phenotype. Misdiagnosis of severe disorders unavoidably affects appropriate treatment and leads to irreversible outcomes for patients, which underlines the importance of molecular diagnosis and genetic analysis. Here we conclude clinical manifestations, molecular mechanism, diagnosis and management of several eczema-related genodermatosis and provide accessible advice to physicians.

Inborn Errors of Immunity Associated with Elevated IgE

OBJECTIVE

To review the characteristic clinical and laboratory features of inborn errors of immunity that are associated with elevated IgE levels DATA SOURCE: Primary peer-reviewed literature.

STUDY SELECTION

Original research articles reviewed include interventional studies, retrospective studies, case-control studies, cohort studies and review articles related to the subject matter.

RESULTS

An extensive literature review was completed to allow for comprehensive evaluation of several monogenic inborn errors of immunity. This review includes a description of the classic clinical features, common infections, characteristic laboratory findings, specific diagnostic methods (when applicable), and genetic basis of disease of each syndrome. A comprehensive flow diagram was created to assist them in the diagnosis and evaluation of patients with elevated IgE levels who may require evaluation for an IEI.

CONCLUSION

IEI should be considered in patients with elevated IgE levels, especially if they have recurrent infections, eczematous dermatitis, malignancy, lymphoproliferation, autoimmunity, and/or connective tissue abnormalities.

Atopy as Immune Dysregulation: Offender Genes and Targets

Allergic diseases are a heterogeneous group of disorders resulting from exaggerated type 2 inflammation. Although typically viewed as polygenic multifactorial disorders caused by the interaction of several genes with the environment, we have come to appreciate that allergic diseases can also be caused by monogenic variants affecting the immune system and the skin epithelial barrier. Through a myriad of genetic association studies and high-throughput sequencing tools, many monogenic and polygenic culprits of allergic diseases have been described. Identifying the genetic causes of atopy has shaped our understanding of how these conditions occur and how they may be treated and even prevented. Precision diagnostic tools and therapies that address the specific molecular pathways implicated in allergic inflammation provide exciting opportunities to improve our care for patients across the field of allergy and immunology. Here, we highlight offender genes implicated in polygenic and monogenic allergic diseases and list targeted therapeutic approaches that address these disrupted pathways.

Effects of the T337M and G391V disease-related variants on human phosphoglucomutase 1: structural disruptions large and small

Phosphoglucomutase 1 (PGM1) plays a central role in glucose homeostasis in human cells. Missense variants of this enzyme cause an inborn error of metabolism, which is categorized as a congenital disorder of glycosylation. Here, two disease-related variants of PGM1, T337M and G391V, which are both located in domain 3 of the four-domain protein, were characterized via X-ray crystallography and biochemical assays. The studies show multiple impacts resulting from these dysfunctional variants, including both short- and long-range structural perturbations. In the T337M variant these are limited to a small shift in an active-site loop, consistent with reduced enzyme activity. In contrast, the G391V variant produces a cascade of structural perturbations, including displacement of both the catalytic phosphoserine and metal-binding loops. This work reinforces several themes that were found in prior studies of dysfunctional PGM1 variants, including increased structural flexibility and the outsized impacts of mutations affecting interdomain interfaces. The molecular mechanisms of PGM1 variants have implications for newly described inherited disorders of related enzymes.

Eosinophilia Associated With Immune Deficiency

The differential diagnosis of eosinophilia is broad and includes infections, malignancies, and atopy as well as inborn errors of immunity (IEI). Certain types of IEIs are known to be associated with elevated numbers of eosinophils and frequently elevated serum IgE, whereas for others the degree and frequency of eosinophilia are less established. The molecular defects underlying IEI are heterogeneous and affect different pathways, which highlights the complex regulations of this cell population within the immune system. In this review, we list and discuss clinical manifestations and therapies of immune deficiency or immune dysregulation disorders associated with peripheral blood or tissue eosinophilia with or without raised IgE levels. We present illustrative case vignettes for the most common entities and propose a diagnostic algorithm aiming to help physicians systematically to evaluate patients with eosinophilia and suspicion of an underlying IEI.

Component of oligomeric Golgi complex 1 deficiency leads to hypoglycemia: a case report and literature review

Background

Congenital disorders of glycosylation (CDG) are a group of metabolic diseases with clinical and genetic heterogeneity, and CDG-IIg is one of the rare reported types of CDG. The aim of this study is to report the clinical manifestations and gene-phenotype characteristics of a rare case of CDG caused by a COG1 gene mutation and review literatures of CDG disease.

Case presentation

The patient was male, and the main clinical symptoms were developmental retardation, convulsion, strabismus, and hypoglycemia, which is rarely reported in CDG-IIg. We treated the patient with glucose infusion and he was recovered from hypoglycemia. Genetic analysis showed that the patient carried the heterozygous intron mutation c.1070 + 3A > G (splicing) in the coding region of the COG1 gene that was inherited from the mother, and the heterozygous mutation c.2492G > A (p. Arg831Gln) in exon 10 of the COG1 gene that was inherited from the father. The genes interacting with COG1 were mainly involved in the transport and composition of the Golgi. The clinical data and laboratory results from a patient diagnosed with CDG-IIg were analyzed, and the causative gene mutation was identified by high-throughput sequencing. The genes and signal pathways related to COG1 were analyzed by Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses.

Conclusions

The c.2492G > A (p. Arg831Gln) mutation in exon 10 of the COG1 gene may be a potential pathogenetic variant for CDG-IIg. Because of the various manifestations of CDG in clinical practice, multidisciplinary collaboration is important for the diagnosis and treatment of this disease.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12887-021-02922-7.

Treatment Options in Congenital Disorders of Glycosylation

Despite advances in the identification and diagnosis of congenital disorders of glycosylation (CDG), treatment options remain limited and are often constrained to symptomatic management of disease manifestations. However, recent years have seen significant advances in treatment and novel therapies aimed both at the causative defect and secondary disease manifestations have been transferred from bench to bedside. In this review, we aim to give a detailed overview of the available therapies and rising concepts to treat these ultra-rare diseases.

Hearing loss in inherited metabolic disorders: A systematic review

Inherited metabolic disorders (IMDs) have been observed in individuals with hearing loss (HL), but IMDs are rarely the cause of syndromic HL. With early diagnosis, management of HL is more effective and cortical reorganization is possible with hearing aids or cochlear implants. This review describes relationships between IMDs and HL in terms of incidence, etiology of HL, pathophysiology, and treatment. Forty types of IMDs are described in the literature, mainly in case reports. Management and prognosis are noted where existing. We also describe IMDs with HL given age of occurrence of HL. Reviewing the main IMDs that are associated with HL may provide an additional clinical tool with which to better diagnose syndromic HL.

Skeletal and Bone Mineral Density Features, Genetic Profile in Congenital Disorders of Glycosylation: Review

Congenital disorders of glycosylation (CDGs) are a heterogeneous group of disorders with impaired glycosylation of proteins and lipids. These conditions have multisystemic clinical manifestations, resulting in gradually progressive complications including skeletal involvement and reduced bone mineral density. Contrary to PMM2-CDG, all remaining CDG, including ALG12-CDG, ALG3-CDG, ALG9-CDG, ALG6-CDG, PGM3-CDG, CSGALNACT1-CDG, SLC35D1-CDG and TMEM-165, are characterized by well-defined skeletal dysplasia. In some of them, prenatal-onset severe skeletal dysplasia is observed associated with early death. Osteoporosis or osteopenia are frequently observed in all CDG types and are more pronounced in adults. Hormonal dysfunction, limited mobility and inadequate diet are common risk factors for reduced bone mineral density. Skeletal involvement in CDGs is underestimated and, thus, should always be carefully investigated and managed to prevent fractures and chronic pain. With the advent of new therapeutic developments for CDGs, the severity of skeletal complications may be reduced. This review focuses on possible mechanisms of skeletal manifestations, risk factors for osteoporosis, and bone markers in reported paediatric and adult CDG patients.

STAT3 Hyper-IgE Syndrome-an Update and Unanswered Questions

The hyper-IgE syndromes (HIES) are a heterogeneous group of inborn errors of immunity sharing manifestations including increased infection susceptibility, eczema, and raised serum IgE. Since the prototypical HIES description 55 years ago, areas of significant progress have included description of key disease-causing genes and differentiation into clinically distinct entities. The first two patients reported had what is now understood to be HIES from dominant-negative mutations in signal transduction and activator of transcription 3 (STAT3-HIES), conferring a broad immune defect across both innate and acquired arms, as well as defects in skeletal, connective tissue, and vascular function, causing a clinical phenotype including eczema, staphylococcal and fungal skin and pulmonary infection, scoliosis and minimal trauma fractures, and vascular tortuosity and aneurysm. Due to the constitutionally expressed nature of STAT3, initial reports at treatment with allogeneic stem cell transplantation were not positive and treatment has hinged on aggressive antimicrobial prophylaxis and treatment to prevent the development of end-organ disease such as pneumatocele. Research into the pathophysiology of STAT3-HIES has driven understanding of the interface of several signaling pathways, including the JAK-STAT pathways, interleukins 6 and 17, and the role of Th17 lymphocytes, and has been expanded by identification of phenocopies such as mutations in IL6ST and ZNF341. In this review we summarize the published literature on STAT3-HIES, present the diverse clinical manifestations of this syndrome with current management strategies, and update on the uncertain role of stem cell transplantation for this disease. We outline key unanswered questions for further study.

Novel form of rhizomelic skeletal dysplasia associated with a homozygous variant in GNPNAT1

BACKGROUND

Studies exploring molecular mechanisms underlying congenital skeletal disorders have revealed novel regulators of skeletal homeostasis and shown protein glycosylation to play an important role.

OBJECTIVE

To identify the genetic cause of rhizomelic skeletal dysplasia in a consanguineous Pakistani family.

METHODS

Clinical investigations were carried out for four affected individuals in the recruited family. Whole genome sequencing (WGS) was completed using DNA from two affected and two unaffected individuals from the family. Sequencing data were processed, filtered and analysed. In silico analyses were performed to predict the effects of the candidate variant on the protein structure and function. Small interfering RNAs (siRNAs) were used to study the effect of Gnpnat1 gene knockdown in primary rat chondrocytes.

RESULTS

The patients presented with short stature due to extreme shortening of the proximal segments of the limbs. Radiographs of one individual showed hip dysplasia and severe platyspondyly. WGS data analyses identified a homozygous missense variant c.226G>A; p.(Glu76Lys) in GNPNAT1, segregating with the disease. Glucosamine 6-phosphate N-acetyltransferase, encoded by the highly conserved gene GNPNAT1, is one of the enzymes required for synthesis of uridine diphosphate N-acetylglucosamine, which participates in protein glycosylation. Knockdown of Gnpnat1 by siRNAs decreased cellular proliferation and expression of chondrocyte differentiation markers collagen type 2 and alkaline phosphatase, indicating that Gnpnat1 is important for growth plate chondrocyte proliferation and differentiation.

CONCLUSIONS

This study describes a novel severe skeletal dysplasia associated with a biallelic, variant in GNPNAT1. Our data suggest that GNPNAT1 is important for growth plate chondrogenesis.

Novel PGM3 compound heterozygous variants with IgE-related dermatitis, lymphopenia, without syndromic features

BACKGROUND

Phosphoglucomutase-3 (PGM3) deficiency is a congenital disorder of glycosylation (CDG) with hyperimmunoglobulin IgE, atopy, and a variable immunological phenotype; most reported patients display dysmorphic features. The aim of the study was to characterize the genotype and phenotype of individuals with newly identified compound heterozygous variants in the phosphate-binding domain of PGM3 in order to better understand phenotypic differences between these patients and published cases.

METHODS

We analyzed PGM3 protein expression, PGM3 enzymatic activity, the presence of other gene variants within the N-glycosylation pathway, and the clinical and immunological manifestations of two affected siblings.

RESULTS

Patients belonged to a non-consanguineous family, presenting with atopic dermatitis, elevated levels of IgE, and CD4⁺ lymphopenia (a more severe phenotype was observed in Patient 2), but lacked dysmorphic features or neurocognitive impairment. Compound heterozygous PGM3 variants were identified, located in the phosphate-binding domain of the enzyme. PGM3 expression was comparable to healthy donors, but L-PHA binding in naïve-CD4+ cells was decreased. Examination of exome sequence identified the presence of one additional candidate variant of unknown significance (VUS) in the N-glycosylation pathway in Patient 2: a variant predicted to have moderate-to-high impact in ALG12.

CONCLUSIONS

Our analysis revealed that L-PHA binding is reduced in naïve-CD4+ cells, which is consistent with decreased residual PGM3 enzymatic activity. Other gene variants in the N-glycosylation pathway may modify patient phenotypes in PGM3 deficiency. This study expands the clinical criteria for when PGM3 deficiency should be considered among individuals with hyper-IgE.

Inborn errors of immunity and metabolic disorders: current understanding, diagnosis, and treatment approaches

Inborn errors of metabolism consist of a heterogeneous group of disorders with various organ systems manifestations, and some metabolic diseases also cause immunological disorders or dysregulation. In this review, metabolic diseases that affect the immunological system and particularly lead to primary immune deficiency will be reviewed. In a patient with frequent infections and immunodeficiency, the presence of symptoms such as growth retardation, abnormal facial appearance, heart, skeletal, lung deformities, skin findings, arthritis, motor developmental retardation, seizure, deafness, hepatomegaly, splenomegaly, impairment of liver function tests, the presence of anemia, thrombocytopenia and eosinophilia in hematological examinations should suggest metabolic diseases for the underlying cause. In some patients, these phenotypic findings may appear before the immunodeficiency picture. Metabolic diseases leading to immunological disorders are likely to be rare but probably underdiagnosed. Therefore, the presence of recurrent infections or autoimmune findings in a patient with a suspected metabolic disease should suggest that immune deficiency may also accompany the picture, and diagnostic examinations in this regard should be deepened.

Clinical Profile of Hyper-IgE Syndrome in India

Introduction: Hyper-IgE Syndrome (HIES) is a rare inborn error of immunity (IEI) characterized by a constellation of symptoms related to susceptibility to Staphylococcal skin and pulmonary infections, eczema, raised serum IgE (>2,000 IU/ml), craniofacial anomalies, and recurrent bone fractures. Data on HIES from the Indian subcontinent is scarce and restricted to small case series and case reports. This is the first compilation of national data on HIES. Materials and Methods: A total 103 cases clinically diagnosed and treated as HIES were analyzed from nine centers. Cases with clinical and/or molecular diagnosis of DOCK8 deficiency were not included. Patients were divided into two groups: group I for whom a heterozygous rare variant of STAT3 was identified, and group II, with clinical features similar to those of AD STAT3 deficiency, but without any genetic diagnosis. Results: Genetic diagnosis was available in 27 patients (26.2%) and all harbored rare variants in the STAT3 gene. Majority of these STAT3 HIES patients presented with recurrent skin abscesses (77.7%) or pneumonia (62.9%) or both (59.2%). Other features included eczema (37%), candidiasis (55.5%), facial dysmorphism (55.5%), recurrent fractures (11.1%), and retained primary teeth (7.4%). Mycobacterial infections were seen in a significant 18.5%. Mortality was seen in three subjects (11.1%). A similar trend in the clinical presentation was observed when all the 103 patients were analyzed together. Twenty percent of patients without a rare variant in the STAT3 gene had an NIH score of ≥40, whereas, 51.9% of STAT3 HIES subjects had scores below the cut off of ≥40. TH17 cell numbers were low in 10/11 (90.9%) STAT3 HIES tested. Rare variants observed were 8 in exon 21; 8 in exon 13; 3 in exon 10; 2 in exon 15, and one each in exon 6, 16, 17, 19, 22, and splice site downstream of exon 12. Seven variants were novel and included F174S, N567D, L404Sfs^*8, G419 =, M329K, T714I, R518X, and a splice site variant downstream of exon 12. Conclusions: The report includes seven novel STAT3 variants, including a rare linker domain nonsense variant and a CC domain variant. Mycobacterial diseases were more frequent, compared to western literature.

Glycans in Immunologic Health and Disease

The surfaces of all living organisms and most secreted proteins share a common feature: They are glycosylated. As the outermost-facing molecules, glycans participate in nearly all immunological processes, including driving host-pathogen interactions, immunological recognition and activation, and differentiation between self and nonself through a complex array of pathways and mechanisms. These fundamental immunologic roles are further cast into sharp relief in inflammatory, autoimmune, and cancer disease states in which immune regulation goes awry. Here, we review the broad impact of glycans on the immune system and discuss the changes and clinical opportunities associated with the onset of immunologic disease.

Two Novel Homozygous Mutations in Phosphoglucomutase 3 Leading to Severe Combined Immunodeficiency, Skeletal Dysplasia, and Malformations

Phosphoglucomutase 3 (PGM3) deficiency is a rare congenital disorder of glycosylation. Most of patients with autosomal recessive hypomorphic mutations in PGM3 encoding for phosphoglucomutase 3 present with eczema, skin and lung infections, elevated serum IgE, as well as neurological and skeletal features. A few PGM3-deficient patients suffer from a more severe disease with nearly absent T cells and severe skeletal dysplasia. We performed targeted next-generation sequencing on two kindred to identify the underlying genetic etiology of a severe combined immunodeficiency with developmental defect. We report here two novel homozygous missense variants (p.Gly359Asp and p.Met423Thr) in PGM3 identified in three patients from two unrelated kindreds with severe combined immunodeficiency, neurological impairment, and skeletal dysplasia. Both variants segregated with the disease in the two families. They were predicted to be deleterious by in silico analysis. PGM3 enzymatic activity was found to be severely impaired in primary fibroblasts and Epstein-Barr virus immortalized B cells from the kindred carrying the p.Met423Thr variant. Our findings support the pathogenicity of these two novel variants in severe PGM3 deficiency.

A missense mutation in a patient with developmental delay affects the activity and structure of the hexosamine biosynthetic pathway enzyme AGX1

O-GlcNAcylation is a post-translational modification catalysed by O-GlcNAc transferase (OGT). Missense mutations in OGT have been associated with developmental disorders, OGT-linked congenital disorder of glycosylation (OGT-CDG), which are characterized by intellectual disability. OGT relies on the hexosamine biosynthetic pathway (HBP) for provision of its UDP-GlcNAc donor. We considered whether mutations in UDP-N-acetylhexosamine pyrophosphorylase (UAP1), which catalyses the final step in the HBP, would phenocopy OGT-CDG mutations. A de novo mutation in UAP1 (NM_001324114:c.G685A:p.A229T) was reported in a patient with intellectual disability. We show that this mutation is pathogenic and decreases the stability and activity of the UAP1 isoform AGX1 in vitro. X-ray crystallography reveals a structural shift proximal to the mutation, leading to a conformational change of the N-terminal domain. These data suggest that the UAP1A229T missense mutation could be a contributory factor to the patient phenotype.

Congenital Disorders of Glycosylation: What Clinicians Need to Know?

Congenital disorders of glycosylation (CDG) are a group of clinically heterogeneous disorders characterized by defects in the synthesis of glycans and their attachment to proteins and lipids. This manuscript aims to provide a classification of the clinical presentation, diagnostic methods, and treatment of CDG based on the literature review and our own experience (referral center in Poland). A diagnostic algorithm for CDG was also proposed. Isoelectric focusing (IEF) of serum transferrin (Tf) is still the method of choice for diagnosing N-glycosylation disorders associated with sialic acid deficiency. Nowadays, high-performance liquid chromatography, capillary zone electrophoresis, and mass spectrometry techniques are used, although they are not routinely available. Since next-generation sequencing became more widely available, an improvement in diagnostics has been observed, with more patients and novel CDG subtypes being reported. Early and accurate diagnosis of CDG is crucial for timely implementation of appropriate therapies and improving clinical outcomes. However, causative treatment is available only for few CDG types.

Chronic Mucocutaneous Candidiasis in Early Life: Insights Into Immune Mechanisms and Novel Targeted Therapies

Children with chronic mucocutaneous candidiasis (CMC) experience recurrent infections with Candida spp. Moreover, immune dysregulation in the early life of these patients induces various autoimmune diseases and affects normal growth and development. The adaptive and innate immune system components play a significant role in anti-fungal response. This response is mediated through IL-17 production by T helper cells. Inborn errors in IL-17-mediated pathways or Candida spp. sensing molecules are known to cause CMC. In this review, we describe underlying immune mechanisms of monogenic primary immune deficiency disorders known to cause CMC. We will explore insights into current management of these patients and novel available therapies.

The Role of Bone Marrow Evaluation in Clinical Allergy and Immunology Practice: When and Why

Allergists and immunologists rely on other specialists for higher risk procedures such as biopsies of the lung or gastrointestinal tract. However, we perform and interpret a handful of procedures ourselves. Training programs have historically required competency for prescribing immunoglobulin infusions, patch testing, rhino laryngoscopy, lung function testing, and provocation testing for airway hyperreactivity even though other specialists often perform them. Bone marrow aspirations and biopsies are not included in fellowship training assessments despite a significant number of marrow evaluations being requested by allergists and immunologists. For example, nearly 1 marrow assessment per month has been requested over 2 years for patients in the Allergy Immunology Clinic at Walter Reed National Military Medical Center. Marrow assessments are often required for diagnosis, monitoring, and treatment-related toxicities. Interpretive and procedural competency would benefit the field given the range of diseases in clinical immunology practice that require marrow assessment. We have generated a comprehensive list of the major conditions that might require bone marrow assessments in any Allergy and Immunology practice. We then summarize the specific tests that must be ordered and show how to determine sample quality. Finally, some providers may desire procedural competency and for those individuals we discuss tips for the procedure.

Heterozygous PGM3 Variants Are Associated With Idiopathic Focal Epilepsy With Incomplete Penetrance

Introduction

Idiopathic focal epilepsy (IFE) is a group of self-limited epilepsies. The etiology for the majority of the patients with IFE remains elusive. We thus screened disease-causing variants in the patients with IFE.

Methods

Whole-exome sequencing was performed in a cohort of 323 patients with IFE. Protein modeling was performed to predict the effects of missense variants. The genotype-phenotype correlation of the newly defined causative gene was analyzed.

Results

Four novel heterozygous variants in PGM3, including two de novo variants, were identified in four unrelated individuals with IFE. The variants included one truncating variant (c.1432C > T/p.Q478X) and three missense variants (c.478C > T/p.P160S, c.1239C > G/p.N413K, and c.1659T > A/p.N553K), which had no allele frequency in the gnomAD database. The missense variants were predicted to be damaging and affect hydrogen bonds with surrounding amino acids. Mutations Q478X, P160S, and N413K were associated with benign childhood epilepsy with centrotemporal electroencephalograph (EEG) spikes. P160S and N413K were located in the inner side of the enzyme active center. Mutation N553K was associated with benign occipital epilepsy with incomplete penetrance, located in the C-terminal of Domain 4. Further analysis demonstrated that previously reported biallelic PGM3 mutations were associated with severe immunodeficiency and/or congenital disorder of glycosylation, commonly accompanied by neurodevelopmental abnormalities, while monoallelic mutations were associated with milder symptoms like IFE.

Conclusion

The genetic and molecular evidence from the present study implies that the PGM3 variants identified in IFE patients lead to defects of the PGM3 gene, suggesting that the PGM3 gene is potentially associated with epilepsy. The genotype-phenotype relationship of PGM3 mutations suggested a quantitative correlation between genetic impairment and phenotypic severity, which helps explain the mild symptoms and incomplete penetrance in individuals with IFE.

Congenital disorders of glycosylation: Still "hot" in 2020

BACKGROUND

Congenital disorders of glycosylation (CDG) are inherited metabolic diseases caused by defects in the genes important for the process of protein and lipid glycosylation. With the ever growing number of the known subtypes and discoveries regarding the disease mechanisms and therapy development, it remains a very active field of study.

SCOPE OF REVIEW

This review brings an update on the CDG-related research since 2017, describing the novel gene defects, pathobiomechanisms, biomarkers and the patients' phenotypes. We also summarize the clinical guidelines for the most prevalent disorders and the current therapeutical options for the treatable CDG.

MAJOR CONCLUSIONS

In the majority of the 23 new CDG, neurological involvement is associated with other organ disease. Increasingly, different aspects of cellular metabolism (e.g., autophagy) are found to be perturbed in multiple CDG.

GENERAL SIGNIFICANCE

This work highlights the recent trends in the CDG field and comprehensively overviews the up-to-date clinical recommendations.