New disorders in carbohydrate metabolism: congenital disorders of glycosylation and their impact on the endocrine system

The Effects of Mesenchymal Stem Cells-Derived Exosomes on Metabolic Reprogramming in Scar Formation and Wound Healing

Pathological scarring results from aberrant cutaneous wound healing due to the overactivation of biological behaviors of human skin fibroblasts, characterized by local inordinate inflammation, excessive extracellular matrix and collagen deposition. Yet, its underlying pathogenesis opinions vary, which could be caused by increased local mechanical tension, enhanced and continuous inflammation, gene mutation, as well as cellular metabolic disorder, etc. Metabolic reprogramming is the process by which the metabolic pattern of cells undergoes a systematic adjustment and transformation to adapt to the changes of the external environment and meet the needs of their growth and differentiation. Therefore, the abnormality of metabolic reprogramming in cells within wounds and scars attaches great importance to scar formation. Mesenchymal stem cells-derived exosomes (MSC-Exo) are the extracellular vesicles that play an important role in tissue repair, cancer treatment as well as immune and metabolic regulation. However, there is not a systematic work to detail the relevant studies. Herein, we gave a comprehensive summary of the existing research on three main metabolisms, including glycometabolism, lipid metabolism and amino acid metabolism, and MSC-Exo regulating metabolic reprogramming in wound healing and scar formation for further research reference.

Exome Sequencing has a high diagnostic rate in sporadic congenital hypopituitarism and reveals novel candidate genes

CONTEXT

The pituitary gland is key for childhood growth, puberty, and metabolism. Pituitary dysfunction is associated with a spectrum of phenotypes, from mild to severe. Congenital Hypopituitarism (CH) is the most commonly reported pediatric endocrine dysfunction with an incidence of 1:4000, yet low rates of genetic diagnosis have been reported.

OBJECTIVE

We aimed to unveil the genetic etiology of CH in a large cohort of patients from Argentina.

METHODS

We performed whole exome sequencing of 137 unrelated cases of CH, the largest cohort examined with this method to date.

RESULTS

Of the 137 cases, 19.1% and 16% carried pathogenic or likely pathogenic variants in known and new genes, respectively, while 28.2% carried variants of uncertain significance. This high yield was achieved through the integration of broad gene panels (genes described in animal models and/or other disorders), an unbiased candidate gene screen with a new bioinformatics pipeline (including genes high loss of function intolerance), and analysis of copy number variants. Three novel findings emerged. First, the most prevalent affected gene encodes the cell adhesion factor ROBO1. Affected children had a spectrum of phenotypes, consistent with a role beyond pituitary stalk interruption syndrome. Second, we found that CHD7 mutations also produce a phenotypic spectrum, not always associated with full CHARGE syndrome. Third, we add new evidence of pathogenicity in the genes PIBF1 and TBC1D32, and report 13 novel candidate genes associated with CH (e.g. PTPN6, ARID5B).

CONCLUSION

Overall, these results provide an unprecedented insight into the diverse genetic etiology of hypopituitarism.

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.

Hypogonadism in Males With Genetic Neurodevelopmental Syndromes

Genetic syndromes that affect the nervous system may also disrupt testicular function, and the mechanisms for these effects may be interrelated. Most often neurological signs and symptoms predominate and hypogonadism remains undetected and untreated, while in other cases, a thorough evaluation of a hypogonadal male reveals previously unrecognized ataxia, movement disorder, muscle weakness, tremor, or seizures, leading to a syndromic diagnosis. Androgen deficiency in patients with neurological diseases may aggravate muscle weakness and fatigue and predispose patients to osteoporosis and obesity. The purpose of this mini review is to provide a current understanding of the clinical, biochemical, histologic, and genetic features of syndromes in which male hypogonadism and neurological dysfunction may coexist and may be encountered by the clinical endocrinologist.

Hyperinsulinism May Be Underreported in Hypoglycemic Patients with Phosphomannomutase 2 Deficiency

Objective

Phosphomannomutase 2 deficiency (PMM2-CDG) is a disorder of protein N-glycosylation with a wide clinical spectrum. Hypoglycemia is rarely reported in PMM2-CDG. In this study, we evaluated cause, treatment options and outcomes in cases with hypoglycemia in the course of PMM2-CDG.

Methods

Clinical records of patients followed with PMM2-CDG within the last two decades were reviewed. Medical data of patients with hypoglycemia were evaluated in more detail. Demographic and clinical findings, organ involvement and laboratory investigations at time of hypoglycemia were recorded. Time of first attack of hypoglycemia, cause, treatment modalities, duration of hypoglycemia (permanent/transient), and duration of treatment, as well as outcome were also recorded. Other published cases with PMM2-CDG and hypoglycemia are also reviewed in order to elucidate characteristics as well as pathophysiology of hypoglycemia.

Results

Nine patients with PMM2-CDG were reviewed, and hypoglycemia was present in three cases. All three had hyperinsulinism as the cause of hypoglycemia. In the first two cases reported here, serum insulin level concurrent with hypoglycemic episodes was elevated, and glucose response was exaggerated during glucagon test, favoring hyperinsulinism. However, in the third case, the serum insulin level at time of hypoglycemia was not so high but hypoglycemia responded well to diazoxide. Hyperinsulinism was permanent in two of these three cases. No genotype-phenotype correlation was observed with respect to hyperinsulinism.

Conclusion

The main cause of hypoglycemia in PMM2-CDG appears to be hyperinsulinism. Although insulin levels at the time of hypoglycemia may not be very high, hypoglycemia in patients with PMM2 responds well to diazoxide.

SRD5A3-CDG: Emerging Phenotypic Features of an Ultrarare CDG Subtype

Background: SRD5A3-CDG is a rare N-glycosylation defect caused by steroid 5 alpha reductase type 3 deficiency. Its key feature is an early severe visual impairment with variable ocular anomalies often leading to diagnosis. Additional symptoms are still poorly defined. In this case study, we discuss 11 genetically confirmed cases, and report on emerging features involving other systems in addition to the eye phenotype.

Methods: In total, 11 SRD5A3-CDG patients in five sets of sibships were included in the study. Data on 9 of 11 patients are as of yet unpublished. Patients’ results on biochemical and genetic investigations and on in-depth phenotyping are presented.

Results: Key diagnostic features of SRD5A3-CDG are ophthalmological abnormalities with early-onset retinal dystrophy and optic nerve hypoplasia. SRD5A3-CDG is also characterized by variable neurological symptoms including intellectual disability, ataxia, and hypotonia. Furthermore, ichthyosiform skin lesions, joint laxity, and scoliosis have been observed in our cohort. We also report additional findings including dystonia, anxiety disorder, gastrointestinal symptoms, and MRI findings of small basal ganglia and mal-rotated hippocampus, whereas previous publications described dysmorphic features as a common finding in SRD5A3, which could not be confirmed in our patient cohort.

Conclusion: The detailed description of the phenotype of this large cohort of patients with SRD5A3-CDG highlights that the key clinical diagnostic features of SRD5A3-CDG are an early onset form of ophthalmological problems in patients with a multisystem disorder with variable symptoms evolving over time. This should aid earlier diagnosis and confirms the need for long-time follow-up of patients.

Anthropometric Phenotype of Patients with PMM2-CDG

Background: Growth failure is commonly reported in children with PMM2-CDG. The aim of the study was to delineate the longitudinal anthropometric phenotype of patients with PMM2-CDG and attempt to find some correlations between the genotype and anthropometric phenotype. Materials and methods: Retrospective chart review of PMM2-CDG patients’ medical records was performed regarding the anthropometric measurements (head circumference, body length/height, body weight, body mass index) and PMM2 variants. Results: A negative tendency of growth evolution was observed. Patients found to be heterozygous for R141H grew slower than other patients. Body weight was correlated with body height. A negative tendency of the growth rate of head circumference was observed. Patients found to be heterozygous for R141H experienced slower growth than other patients. Conclusions: Long-term observational studies are essential to characterize the anthropometric phenotype. The body growth failure, as well as head circumference growth failure, were more severe in patients found to be heterozygous for R141H.

Should patients with Phosphomannomutase 2-CDG (PMM2-CDG) be screened for adrenal insufficiency?

PMM2-CDG is the most common congenital disorder of glycosylation (CDG) accounting for almost 65% of known CDG cases affecting N-glycosylation. Abnormalities in N-glycosylation could have a negative impact on many endocrine axes. There is very little known on the effect of impaired N-glycosylation on the hypothalamic-pituitary-adrenal axis function and whether CDG patients are at risk of secondary adrenal insufficiency and decreased adrenal cortisol production. Cortisol and ACTH concentrations were simultaneously measured between 7:44 am to 1 pm in forty-three subjects (20 female, median age 12.8 years, range 0.1 to 48.6 years) participating in an ongoing international, multi-center Natural History study for PMM2-CDG (ClinicalTrials.gov Identifier: NCT03173300). Of the 43 subjects, 11 (25.6%) had cortisol below 5 μg/dl and low to normal ACTH levels, suggestive of secondary adrenal insufficiency. Two of the 11 subjects have confirmed central adrenal insufficiency and are on hydrocortisone replacement and/or stress dosing during illness; 3 had normal and 1 had subnormal cortisol response to ACTH low-dose stimulation test but has not yet been started on therapy; the remaining 5 have upcoming stimulation testing planned. Our findings suggest that patients with PMM2-CDG may be at risk for adrenal insufficiency. Monitoring of morning cortisol and ACTH levels should be part of the standard care in patients with PMM2-CDG.

Expanding the phenotype, genotype and biochemical knowledge of ALG3-CDG

Congenital disorders of glycosylation (CDGs) are a continuously expanding group of monogenic disorders of glycoprotein and glycolipid biosynthesis that cause multisystem diseases. Individuals with ALG3-CDG frequently exhibit severe neurological involvement (epilepsy, microcephaly, and hypotonia), ocular anomalies, dysmorphic features, skeletal anomalies, and feeding difficulties. We present 10 unreported individuals diagnosed with ALG3-CDG based on molecular and biochemical testing with 11 novel variants in ALG3, bringing the total to 40 reported individuals. In addition to the typical multisystem disease seen in ALG3-CDG, we expand the symptomatology of ALG3-CDG to now include endocrine abnormalities, neural tube defects, mild aortic root dilatation, immunodeficiency, and renal anomalies. N-glycan analyses of these individuals showed combined deficiencies of hybrid glycans and glycan extension beyond Man₅ GlcNAc₂ consistent with their truncated lipid-linked precursor oligosaccharides. This spectrum of N-glycan changes is unique to ALG3-CDG. These expanded features of ALG3-CDG facilitate diagnosis and suggest that optimal management should include baseline endocrine, renal, cardiac, and immunological evaluation at the time of diagnosis and with ongoing monitoring.

Primary ovarian insufficiency in a female with phosphomannomutase-2 gene (PMM2) mutations for congenital disorder of glycosylation

Primary ovarian insufficiency (POI) is a highly heterogeneous condition, and its underlying causes remain to be clarified in a large fraction of patients. Congenital disorders of glycosylation (CDG) are multisystem diseases caused by mutations of a number of genes involved in N-glycosylation or O-glycosylation, and the most frequent form is PMM2-CDG (alias, CDG-Ia) resulting from biallelic mutations in PMM2 encoding phosphomannomutase-2 involved in N-glycosylation. Here, we examined a 46,XX Japanese female with syndromic POI accompanied by an undetectable level of serum anti-Müllerian hormone (AMH). Whole exome sequencing identified biallelic pathogenic mutations of PMM2 (a novel c.34G>C:p.(Asp12His) of maternal origin and a recurrent c.310C>G:p.(Leu104Val) of paternal origin) (NM_000303.3), and N-glycosylation studies detected asialotransferrin and disialotransferrin characteristic of PMM2-CDG, in addition to normally glycosylated tetrasialotransferrin. Clinical assessment showed cerebellar hypotrophy, which is a fairly characteristic and highly prevalent feature in PMM2-CDG, together with multiple non-specific features reported in PMM2-CDG such as characteristic face, intellectual disability, skeletal abnormalities, and low blood antithrombin III value. These results including the undetectable level of serum AMH, in conjunction with previously reported findings suggestive of the critical role of glycosylation in oocyte development and function, imply that PMM2-CDG almost invariably leads to POI primarily because of the defective oogenesis and/or oocyte-dependent early folliculogenesis rather than the compromised bioactivity of FSH/LH with defective glycosylation. Thus, it is recommended to examine PMM2 in patients with syndromic POI, especially in those with cerebellar ataxia/hypotrophy.

New Insights into Potocki-Shaffer Syndrome: Report of Two Novel Cases and Literature Review

Potocki-Shaffer syndrome (PSS) is a rare non-recurrent contiguous gene deletion syndrome involving chromosome 11p11.2. Current literature implies a minimal region with haploinsufficiency of three genes, ALX4 (parietal foramina), EXT2 (multiple exostoses), and PHF21A (craniofacial anomalies, and intellectual disability). The rest of the PSS phenotype is still not associated with a specific gene. We report a systematic review of the literature and included two novel cases. Because deletions are highly variable in size, we defined three groups of patients considering the PSS-genes involved. We found 23 full PSS cases (ALX4, EXT2, and PHF21A), 14 cases with EXT2-ALX4, and three with PHF21A only. Among the latter, we describe a novel male child showing developmental delay, café-au-lait spots, liner postnatal overgrowth and West-like epileptic encephalopathy. We suggest PSS cases may have epileptic spasms early in life, and PHF21A is likely to be the causative gene. Given their subtle presentation these may be overlooked and if left untreated could lead to a severe type or deterioration in the developmental plateau. If our hypothesis is correct, a timely therapy may ameliorate PSS phenotype and improve patients’ outcomes. Our analysis also shows PHF21A is a candidate for the overgrowth phenotype.

COG6-CDG: Expanding the phenotype with emphasis on glycosylation defects involved in the causation of male disorders of sex development

COG6-congenital disorder of glycosylation (COG6-CDG) is caused by biallelic mutations in COG6. To-date, 12 variants causing COG6-CDG in less than 20 patients have been reported. Using whole exome sequencing we identified two siblings with a novel homozygous deletion of 26 bp in COG6, creating a splicing variant (c.518_540 + 3del) and a shift in the reading frame. The phenotype of COG6-CDG includes growth and developmental retardation, microcephaly, liver and gastrointestinal disease, hypohydrosis and recurrent infections. We report two patients with novel phenotypic features including bowel malrotation and ambiguous genitalia, directing attention to the role of glycoprotein metabolism in the causation of disorders of sex development (DSD). Searching the glycomic literature, we identified 14 CDGs including males with DSD, a feature not previously accentuated. This study broadens the genetic and phenotypic spectrum of COG6-CDG and calls for increasing awareness to the central role of glycosylation processes in development of human sex and genitalia.

Therapeutic approaches in Congenital Disorders of Glycosylation (CDG) involving N-linked glycosylation: an update

Congenital disorders of glycosylation (CDG) are a group of clinically and genetically heterogeneous metabolic disorders. Over 150 CDG types have been described. Most CDG types are ultrarare disorders. CDG types affecting N-glycosylation are the most common type of CDG with emerging therapeutic possibilities. This review is an update on the available therapies for disorders affecting the N-linked glycosylation pathway. In the first part of the review, we highlight the clinical presentation, general principles of management, and disease-specific therapies for N-linked glycosylation CDG types, organized by organ system. The second part of the review focuses on the therapeutic strategies currently available and under development. We summarize the successful (pre-) clinical application of nutritional therapies, transplantation, activated sugars, gene therapy, and pharmacological chaperones and outline the anticipated expansion of the therapeutic possibilities in CDG. We aim to provide a comprehensive update on the treatable aspects of CDG types involving N-linked glycosylation, with particular emphasis on disease-specific treatment options for the involved organ systems; call for natural history studies; and present current and future therapeutic strategies for CDG.

Congenital disorders of glycosylation

Congenital disorders of glycosylation are a genetically and clinically heterogeneous group of >130 diseases caused by defects in various steps along glycan modification pathways. The vast majority of these monogenic diseases are autosomal recessive and have multi-systemic manifestations, mainly growth failure, developmental delay, facial dysmorphisms, and variable coagulation and endocrine abnormalities. Carbohydrate deficient transferrin (CDT) and protein-linked glycan analysis with mass spectrometry can diagnose some subtypes of congenital disorders of glycosylation (CDG), while many currently rely on massively parallel genomic sequencing for diagnosis. Early detection is important, as a few of these disorders are treatable. Molecular and biochemical techniques continue to further our understanding of this rapidly expanding group of clinically and genetically diverse disorders.

Inborn errors of metabolism associated with hyperglycaemic ketoacidosis and diabetes mellitus: narrative review

Inborn errors of metabolism (IEM) are heterogeneous group of disorders that might present in the clinics or emergency departments in different phenotypes, and one of these is a diabetes scenario. Diabetes is the most common endocrine disorder among children. The mechanism of how IEM could lead to diabetes is unclear; however, the postulated pathogenesis consists of three mechanisms: 1) accumulation of toxic substance in the gland, ruining structure and normal functionality, 2) disturbing energy availability required for hormone synthesis and 3) defect of complex molecules. The differential diagnosis of IEM associated with hyperglycaemic ketoacidosis and diabetes include: organic acidemias specifically propionic acidemia, methylmalonic acidemia, isovaleric acidemia, hereditary hemochromatosis, aceruloplasminemia, holocarboxylase synthetase deficiency, β-ketothiolase deficiency and finally, cystinosis, Rogers syndrome (thiamine-responsive megaloblastic anaemia) and congenital disorders of glycosylation type Ia. Clinical approach will help in ready diagnosis and treatment for IEM disorders in early detection of diabetes. In this review, we will discuss the differential diagnosis, clinical features and diagnostic approaches of IEM presenting as hyperglycaemic ketoacidosis and diabetes.

DPAGT1 Deficiency with Encephalopathy (DPAGT1-CDG): Clinical and Genetic Description of 11 New Patients

Pathogenic mutations in DPAGT1 cause a rare type of a congenital disorder of glycosylation termed DPAGT1-CDG or, alternatively, a milder version with only myasthenia known as DPAGT1-CMS. Fourteen disease-causing mutations in 28 patients from 10 families have previously been reported to cause the systemic form, DPAGT1-CDG. We here report on another 11 patients from 8 families and add 10 new mutations. Most patients have a very severe disease course, where common findings are pronounced muscular hypotonia, intractable epilepsy, global developmental delay/intellectual disability, and early death. We also present data on three affected females that are young adults and have a somewhat milder, stable disease. Our findings expand both the molecular and clinical knowledge of previously published data but also widen the phenotypic spectrum of DPAGT1-CDG.

Mortality in Children With Early-Detected Congenital Central Hypothyroidism

CONTEXT

Approximately 60% to 80% of patients with congenital central hypothyroidism (CH-C) have multiple pituitary hormone deficiencies (MPHDs), making CH-C a potentially life-threatening disease. Data on mortality in patients with CH-C are lacking.

OBJECTIVE

To study the mortality rate in pediatric patients with early-detected and treated CH-C in the Netherlands and to investigate whether causes of death were related to pituitary hormone deficiencies.

METHODS

Overall mortality rate, infant mortality rate (IMR), and under-5 mortality rate were calculated in all children with CH-C detected by neonatal screening between 1 January 1995 and 1 January 2013. Medical charts were reviewed to establish causes of death.

RESULTS

A total of 139 children with CH-C were identified, of which 138 could be traced (82 with MPHD, 56 with isolated CH-C). Total observation time was 1414 years with a median follow-up duration of 10.2 years. The overall mortality rate was 10.9% (15/138). IMR and under-5 mortality rate were 65.2/1000 (9/138) and 101.4/1000 (14/138), respectively, compared with an IMR of 4.7/1000 and under-5 mortality of 5.4/1000 live-born children in the Netherlands during the same time period (P < 0.0001). Main causes of death were severe congenital malformations in six patients, asphyxia in two patients, and congenital or early neonatal infection in two patients. Pituitary hormone deficiency was noted as cause of death in only one infant.

CONCLUSION

We report an increased mortality rate in patients with early-detected CH-C that does not seem to be related to endocrine disease. This suggests that mortality due to pituitary insufficiency is low in patients with early-detected and early-treated CH-C.

A Population-Based Study on Congenital Disorders of Protein N- and Combined with O-Glycosylation Experience in Clinical and Genetic Diagnosis

OBJECTIVE

To describe the clinical, biochemical, and genetic features of patients with congenital disorders of glycosylation (CDG) identified in Spain during the last 20 years.

STUDY DESIGN

Patients were selected among those presenting with multisystem disease of unknown etiology. The isoforms of transferrin and of ApoC3 and dolichols were analyzed in serum; phosphomannomutase and mannosephosphate isomerase activities were measured in fibroblasts. Conventional or massive parallel sequencing (customized panel or Illumina Clinical-Exome Sequencing TruSight One Gene Panel) was used to identify genes and mutations.

RESULTS

Ninety-seven patients were diagnosed with 18 different CDG. Eighty-nine patients had a type 1 transferrin profile; 8 patients had a type 2 transferrin profile, with 6 of them showing an alteration in the ApoC3 isoform profile. A total of 75% of the patients had PMM2-CDG presenting with a heterogeneous mutational spectrum. The remaining patients showed mutations in any of the following genes: MPI, PGM1, GFPT1, SRD5A3, DOLK, DPGAT1, ALG1, ALG6, RFT1, SSR4, B4GALT1, DPM1, COG6, COG7, COG8, ATP6V0A2, and CCDC115.

CONCLUSION

Based on literature and on this population-based study of CDG, a comprehensive scheme including reported clinical signs of CDG is offered, which will hopefully reduce the timeframe from clinical suspicion to genetic confirmation. The different defects of CDG identified in Spain have contributed to expand the knowledge of CDG worldwide. A predominance of PMM2 deficiency was detected, with 5 novel PMM2 mutations being described.

Congenital disorders of glycosylation and intellectual disability

The congenital disorders of glycosylation (CDG) are a rapidly growing group of inborn errors of metabolism that result from defects in the synthesis of glycans. Glycosylation is a major post-translational protein modification and an estimated 2% of the human genome encodes proteins for glycosylation. The molecular bases for the current 60 disorders, affecting approximately 800 individuals, have been identified, many in the last 5 years. CDG should be considered in any multi-system syndrome or single tissue disorder not explained by the identification of another disorder. The initial clinical presentation varies significantly among individuals, even between affected siblings. However, two thirds of the known CDGs are associated with intellectual disabilities and most affected individuals need support services throughout their lives. Additional disorders of glycosylation are likely to be characterized over time.

rhIGF-1 Therapy for Growth Failure and IGF-1 Deficiency in Congenital Disorder of Glycosylation Ia (PMM2 Deficiency)

Background. Congenital disorders of glycosylation (CDG) are a group of rare disorders in which glycosylation required for proper protein-protein interactions and protein stability is disrupted, manifesting clinically with multiple system involvement and growth failure. The insulin-like growth factor (IGF) system plays an important role in childhood growth and has been shown to be dysfunctional with low IGF-1 levels in children with CDG type Ia (PMM2 deficiency). Case report. A 3-year-old Caucasian male with failure to thrive was diagnosed with PMM2-CDG at 5 months of age. Initially, his length and weight were less than −2 standard deviation score, IGF-1 <25 ng/mL (normal 55-327 ng/mL), IGFBP-3 1.0 µg/mL (normal 0.7-3.6 ng/mL), and acid-labile subunit 1.3 mg/L (normal 0.7-7.9 mg/L). Despite aggressive feeding, he continued to show poor linear growth and weight gain. At 17 months, he underwent an IGF-1 generation test with growth hormone (0.1 mg/kg/d) for 7 days; baseline IGF-1of 27 ng/mL (normal 55-327 ng/mL) stimulated to only 33 ng/mL. Recombinant human IGF-1 (rhIGF-1) therapy (up to 130 µg/kg/dose twice daily) was initiated at 21 months of age resulting in an excellent linear growth response with height increasing from −2.73 to −1.39 standard deviation score over 22 months. IGF-1 and IGFBP-3 levels also increased. Conclusion. This is the first case report of rhIGF-1 therapy in a patient with PMM2-CDG. The child had an excellent linear growth response. These results provide additional in vivo evidence for IGF dysfunction in PMM2-CDG and suggest that rhIGF-1 may be a novel treatment for growth failure in PMM2-CDG.

Thyroid function in PMM2-CDG: diagnostic approach and proposed management

Glycoproteins are essential in the production, transport, storage and regulation of thyroid hormones. Altered glycosylation has a potential impact on thyroid function. Abnormal thyroid function tests have been described in patients with congenital disorders of glycosylation. We evaluated the reliability of biochemical markers and investigated thyroid function in 18 PMM2-CDG patients. We propose an expectative therapeutic approach for neonates with thyroid abnormalities in CDG.

Endocrine manifestations related to inherited metabolic diseases in adults

Most inborn errors of metabolism (IEM) are recessive, genetically transmitted diseases and are classified into 3 main groups according to their mechanisms: cellular intoxication, energy deficiency, and defects of complex molecules. They can be associated with endocrine manifestations, which may be complications from a previously diagnosed IEM of childhood onset. More rarely, endocrinopathies can signal an IEM in adulthood, which should be suspected when an endocrine disorder is associated with multisystemic involvement (neurological, muscular, hepatic features, etc.). IEM can affect all glands, but diabetes mellitus, thyroid dysfunction and hypogonadism are the most frequent disorders. A single IEM can present with multiple endocrine dysfunctions, especially those involving energy deficiency (respiratory chain defects), and metal (hemochromatosis) and storage disorders (cystinosis). Non-autoimmune diabetes mellitus, thyroid dysfunction and/or goiter and sometimes hypoparathyroidism should steer the diagnosis towards a respiratory chain defect. Hypogonadotropic hypogonadism is frequent in haemochromatosis (often associated with diabetes), whereas primary hypogonadism is reported in Alström disease and cystinosis (both associated with diabetes, the latter also with thyroid dysfunction) and galactosemia. Hypogonadism is also frequent in X-linked adrenoleukodystrophy (with adrenal failure), congenital disorders of glycosylation, and Fabry and glycogen storage diseases (along with thyroid dysfunction in the first 3 and diabetes in the last). This is a new and growing field and is not yet very well recognized in adulthood despite its consequences on growth, bone metabolism and fertility. For this reason, physicians managing adult patients should be aware of these diagnoses.

Pubertal development in ALG6 deficiency (congenital disorder of glycosylation type Ic)

Information on the hypothalamic pituitary ovarian axis in congenital disorders of glycosylation (CDG) females is scarce. Varying hormonal profiles and degrees of virilization in CDG females suggest a spectrum of yet unidentified mechanisms affected by impaired N-glycosylation. We describe an ALG6D woman who completed puberty with normal gonadotropins and testosterone levels, no virilization, and regular menses. Hormonal follow-up of CDG females is necessary to improve our understanding of the role of glycosylation in pubertal development.

Presentation of congenital disorders of glycosylation type 1a

This case outlines a classic presentation of the most common type of a recently categorized set of disorders known as congenital disorders of glycosylation.

Congenital disorder of glycosylation type Ia: heterogeneity in the clinical presentation from multivisceral failure to hyperinsulinaemic hypoglycaemia as leading symptoms in three infants with phosphomannomutase deficiency

We describe three patients with congenital disorder of glycosylation (CDG) type Ia, all of whom had persistent hyperinsulinaemic hypoglycaemia responding to diazoxide therapy as a common feature. The first patient, an infant girl, presented with recurrent vomiting, failure to thrive, liver impairment, hypothyroidism and a pericardial effusion. The second patient, also female, had a milder disease with single organ involvement, presenting as isolated hyperinsulinaemic hypoglycaemia, not associated with any cognitive impairment. The third patient, a boy presented with multi-organ manifestations including congenital hypothyroidism, persistent hyperinsulinaemic hypoglycaemia, coagulopathy, olivopontocerebellar hypoplasia and recurrent pancreatitis. All three patients had a type 1 serum transferrin isoform pattern, and were subsequently found to have low phosphomannomutase activity, confirming the diagnosis of CDG type Ia. Our findings emphasize that CDG should be considered as a differential diagnosis in patients with persistent hyperinsulinaemic hypoglycaemia and that it may even occasionally be the leading symptom in CDG Ia.

Long-term evolution of eight Spanish patients with CDG type Ia: typical and atypical manifestations

Congenital disorder of glycosylation Ia (CDG-Ia) is a metabolic disease with a broad spectrum of clinical signs, including recently described mild phenotypes. Our aim was to describe the clinical presentation and follow-up of eight CDG-Ia patients highlighting atypical features and aspects of evolution of the disease. CDG diagnosis was confirmed by enzymatic analysis of phosphomannomutase (PMM2) and molecular studies of the PMM2 gene. Four neonates presented with cerebral haemorrhage (1), failure to thrive (2) and non-immune hydrops (1) and a fatal course to death (2); pathological examination of the brain in one case revealed olivopontocerebellar atrophy of prenatal origin. During infancy failure to thrive, coagulopathy and hepatopathy were the most significant causes of morbidity, but these disappeared after the first years of life in most patients. Three patients are currently in their 20s; they present mental retardation and severe motor impairment but no acute decompensations were noticed after the first decade of life. They do not present spinal or thoracic deformities otherwise observed in patients from northern countries. A 10-year-old patient who manifested gastrointestinal dysfunction in early childhood showed normal neurodevelopment. Mutation analysis of the PMM2 gene showed great variability, with all patients being compound heterozygous for two different mutations. Long-term evolution in our patients indicates that CDG-Ia is a stable systemic and neurological condition after the first decade of life. The diverse phenotypes and atypical manifestations in our series may be due to their genetic heterogeneity.

IGF system in children with congenital disorders of glycosylation

OBJECTIVE

The function of IGF system components is affected by their glycosylation status in vitro. However, little is known about the role of glycosylation status of these components in vivo. In this study we determined the impact of glycosylation on the endocrine IGF system in children with the rare syndrome of congenital disorders of glycosylation (CDG).

DESIGN

Analyses of serum samples from children with CDG and healthy controls.

PATIENTS

Children with CDG (N = 12) were recruited as part of a separate clinical study of mannose therapy at the Mayo Clinic. Serum from control children (N = 11) were obtained as routine samples before discard.

MEASUREMENTS

Levels and glycosylation state of components of the IGF system and ability to form physiologically relevant ternary complexes composed of IGF, IGFBP-3, and an acid-labile subunit (ALS).

RESULTS

Serum levels of IGF-1, IGF-2, ALS, and IGFBP-3 were reduced (P < 0.05) in children with CDG when compared to controls. Immunoblot analysis showed incomplete glycosylation of ALS and IGFBP-3 and impaired ternary complex formation in CDG. Partial normalization of ALS and IGFBP-3 glycosylation was associated with improvement in linear growth in a child with CDG-Ib during initiation of oral mannose therapy.

CONCLUSIONS

Inadequate glycosylation of IGFBP-3 and ALS has a negative effect on the function of these proteins in vivo. This study provides the first evidence in humans for the importance of glycosylation on components of the IGF system.

The clinical spectrum of phosphomannomutase 2 deficiency (CDG-Ia)

Congenital disorders of glycosylation are a clinically and genetically heterogeneous group of disorders resulting from abnormal glycosylation of various glycoconjugates. The first description of congenital disorders of glycosylation was published in the early 80s and once screening tests for glycosylation disorders (CDGs) became readily available, CDG-Ia became the most frequently diagnosed CDG subtype. CDG-Ia is pan-ethnic and the spectrum of the clinical manifestations is still evolving: it spans from severe hydrops fetalis and fetal loss to a (nearly) normal phenotype. However, the most common presentation in infancy is of a multisystem disorder with central nervous system involvement.

Clinical features in adults with congenital disorders of glycosylation type Ia (CDG-Ia)

Congenital disorders of glycosylation (CDG) are a group of metabolic disorders resulting from defective synthesis of N-linked oligosaccharides. CDG-Ia is the most common of the 21 known types defined by defects in different steps of the synthetic pathway. An increasing number of American adults with CDG-Ia are being recognized but little is documented on the morbidity and mortality in this population. These adults have moderate mental retardation, ataxia, retinitis pigmentosa, peripheral neuropathy, kyphoscoliosis, and endocrinopathies. Four adults with CDG-Ia, ages 19-36 years old are presented. All are active, dysarthric conversant adults with moderate cognitive impairment. They are ataxic and wheelchair dependent, however, only the oldest man shows significant muscle atrophy. All have diagnosed peripheral neuropathy. Three of four remain on anticonvulsants with only occasional seizures, none have had stroke-like episodes since their teen years. Their skeletal issues include significant kyphoscoliosis, joint contractures, and osteopenia. Retinitis pigmentosa and myopia complicate their functional vision. The women do not menstruate and the men have small testes resulting from hypogonadotropic hypogonadism. Documentation of clinical complications and successful management strategies in adults with CDG will improve their quality of life and allow more informed prognostic discussions with families of younger affected individuals.

Recent advances in hyperinsulinemic hypoglycemia of infancy

Hyperinsulinemia-induced hypoglycemia is the most common cause of persistent hypoglycemia in adults, children, and infants. Our understanding of the disorders responsible for this type of hypoglycemia has been increasing due to the recent discoveries in the molecular and biochemical regulation of insulin secretion. In this article, we review the current knowledge of the pathophysiology, clinical presentation, and diagnosis of disorders that cause hyperinsulinemic hypoglycemia of infancy. We highlight the distinction between the diffuse and focal forms of the disease, especially the promising results with (18)F-L-dopa positive emission tomography (PET) scanning for preoperative localization and distinction to guide the extent of surgical removal of pancreatic tissue that may result in cure rather than persistence of disturbed carbohydrate metabolism.

CONCLUSION

Despite all these discoveries, much remains to be learned, as currently about one third of infants with hyperinsulinemic hypoglycemia have no identifiable cause.

Clinical and molecular characterization of the first adult congenital disorder of glycosylation (CDG) type Ic patient

Congenital disorder of glycosylation (CDG) type Ic, the second largest subtype of CDG, is caused by mutations in human ALG6 (hALG6). This gene encodes the alpha1,3-glucosyltransferase that catalyzes transfer of the first glucose residue to the lipid-linked oligosaccharide precursor for N-linked glycosylation. In this report, we describe the first adult patient diagnosed with CDG-Ic, carrying two previously unknown mutations. The first is a three base deletion (897-899delAAT) leading to the loss of I299, the second is an intronic mutation (IVS7 + 2T > G) that causes aberrant splicing. Wildtype hALG6, delivered by a lentiviral vector into patient's fibroblasts, clearly improves the biochemical phenotype, which confirms that the mutations are disease-causing. Striking clinical findings include limb deficiencies in the fingers, resembling brachydactyly type B, a deep vein thrombosis, pseudotumor cerebri, and endocrine disturbances with pronounced hyperandrogenism and virilization. However, even in adulthood, this patient shows normal magnetic resonance imaging of the brain.

Construction of a natural panel of 11p11.2 deletions and further delineation of the critical region involved in Potocki-Shaffer syndrome

Potocki-Shaffer syndrome (PSS) is a contiguous gene deletion syndrome that results from haploinsufficiency of at least two genes within the short arm of chromosome 11[del(11)(p11.2p12)]. The clinical features of PSS can include developmental delay, mental retardation, multiple exostoses, parietal foramina, enlarged anterior fontanel, minor craniofacial anomalies, ophthalmologic anomalies, and genital abnormalities in males. We constructed a natural panel of 11p11.2-p13 deletions using cell lines from 10 affected individuals, fluorescence in situ hybridization (FISH), microsatellite analyses, and array-based comparative genomic hybridization (array CGH). We then compared the deletion sizes and clinical features between affected individuals. The full spectrum of PSS manifests when deletions are at least 2.1 Mb in size, spanning from D11S1393 to D11S1385/D11S1319 (44.6-46.7 Mb from the 11p terminus) and encompassing EXT2, responsible for multiple exostoses, and ALX4, causing parietal foramina. Yet one subject with parietal foramina whose deletion does not include ALX4 indicates that ALX4 in this subject may be rendered functionally haploinsufficient by a position effect. Based on comparative deletion mapping of eight individuals with the full PSS syndrome including mental retardation and two PSS families with no mental retardation, at least one gene related to mental retardation is likely located between D11S554 and D11S1385/D11S1319, 45.6-46.7 Mb from the 11p terminus.

Body composition in children with galactosaemia

Body composition in classical galactosaemia has not been studied. Patients with classical galactosaemia, an inherited disorder of galactose metabolism caused by deficiency of galactose-1-phosphate uridyltransferase (GALT, EC 2.7.7.10), might be at risk for an abnormal body composition because of intrinsic factors related to galactosaemia and/or diet-related factors. The aim of this study was to evaluate the body composition of children with classical galactosaemia. The studied population was a previously reported group of classical galactosaemia patients (13 male and 27 female, ages 3-17 years) with decreased height, weight, weight-for-height and insulin-like growth factor-I (IGF-I) Z-scores. Body composition data were obtained by dual-energy X-ray absorptiometry (DXA). In order to correct for height, fat mass (FM) and lean tissue mass (LTM) were divided by squared height. Mid-parental target height Z-scores were assessed and compared to actual height Z-scores. Linear and multiple regression analysis were done to investigate the relationship between body composition and IGF-I, dietary intake and growth data. We found decreased height Z-scores when compared to mid-parental target height Z-scores. Mean scores for FM and LTM (both adjusted for height) were decreased. LTM (adjusted for height) and height Z-score were correlated with IGF-I Z-score. FM (adjusted for height) was correlated with soy intake. No correlation was found between soy intake and IGF-I Z-score. In this limited group of patients, height is decreased and body composition is abnormal. The decreased levels of IGF-I and/or soy nutrition might play a role in these findings.

Congenital disorders of glycosylation: a booming chapter of pediatrics

PURPOSE OF REVIEW

The detection and identification of new congenital disorders of glycosylation continues at a rapid pace. Sine June 2003, four new congenital disorders of glycosylation have been reported, making a total of 20 diseases (on average nearly 1 disease per year since the first report in 1980; 12 of these congenital disorders of glycosylation were identified in the past 6 years).

RECENT FINDINGS

Three of these newly discovered CDG are caused by defects in early steps of dolichol-linked oligosaccharide biosynthesis. Affected patients have a neurologic or a multisystem disease. The fourth new CDG is a completely new CDG type caused by a defect in an endoplasmic reticulum-Golgi shuttle protein carrying multiple glycosyltransferases and nucleotide-sugar transporters.

SUMMARY

Disorders of nearly all organs and systems have been reported and continue to be reported in congenital disorders of glycosylation. Therefore, it is strongly recommended that congenital disorders of glycosylation be considered in any child with an unexplained clinical syndrome.

Differential diagnosis and management of neonatal hypoglycemia

Persistent hypoglycemia in the neonate is most often caused by hyperinsulinemia. Recent discoveries in the molecular and biochemical regulation of insulin secretion have increased dramatically our understanding of disorders responsible for syndromes of hyperinsulinemic hypoglycemia. This article focuses on defects and disorders of the KATP channel, activating mutation of glucokinase and glutamate dehydrogenase, and other disorders that may be associated with specific phenotypes to permit appropriate targeted therapies. It is essential to evaluate these entities carefully because of the emerging evidence that at least half, if not more, have focal disease, which can be cured by local excision rather than diffuse disease, which may not be cured even after near total pancreatectomy with risk for future diabetes. Delay in diagnosis may be associated with developmental delay. The mechanisms of hypoglycemia remain incompletely understood.