Neurological presentation in pediatric patients with congenital disorders of glycosylation type Ia

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.

Association between acute complications in PMM2-CDG patients and haemostasis anomalies: Data from a multicentric study and suggestions for acute management

OBJECTIVES

Patients with PMM2-CDG develop acute events (stroke-like episodes (SLEs), thromboses, haemorrhages, seizures, migraines) associated with both clotting factors (factor XI) and coagulation inhibitors (antithrombin, protein C and protein S) deficiencies. The aim of the study was to correlate acute events to haemostasis and propose practical guidelines.

METHODS

In this multicentric retrospective study, we evaluated clinical, radiological, haemostasis and electroencephalography data for PMM2-CDG patients hospitalized for acute events. Cerebral events were classified as thrombosis, haemorrhage, SLE, or "stroke mimic" (SM: normal brain imaging or evoking a migraine).

RESULTS

Thirteen patients had a total of 31 acute episodes: 27 cerebral events with 7 SLEs, 4 venous thromboses, 4 haemorrhages (3 associated with thrombosis), 15 SMs at a mean age of 7.7 years; 4 non-cerebral thromboses, one of which included bleeding. A trigger was frequently involved (infection, head trauma). Although sometimes normal at baseline state, factor XI, antithrombin and protein C levels decreased during these episodes. No correlation between haemostasis anomalies and type of acute event was found.

DISCUSSION

Acute events in PMM2-CDG are not negligible and are associated with haemostasis anomalies. An emergency protocol is proposed for their prevention and treatment (https://www.filiere-g2m.fr/urgences). For cerebral events, brain Magnetic Resonance Imaging with perfusion weight imaging and diffusion sequences, electroencephalogram and haemostasis protein levels guide the treatment: anticoagulation, antithrombin or fresh frozen plasma supplementation, antiepileptic therapy. Preventing bleeding and thrombosis is required in cases of surgery, prolonged immobilization, hormone replacement therapy.

CONCLUSION

Acute events in PMM2-CDG are associated with abnormal haemostasis, requiring practical guidance.

Stroke-Like Episodes in PMM2-CDG: When the Lack of Other Evidence Is the Only Evidence

Phosphomannomutase 2 deficiency (PMM2-CDG) is the most frequent congenital disorder of glycosylation. PMM2-CDG patients develop chronic cerebellar atrophy as a neurological hallmark. However, other acute neurological phenomena such as stroke-like episodes (SLE), epilepsy, migraine, and cerebrovascular events, may also occur, and they are frequently the cause of disability and impaired quality of life. Among these, SLE are among the most stressful situations for families and doctors, as their risk factors are not known, their underlying pathomechanisms remain undiscovered, and clinical guidelines for diagnosis, prevention, and treatment are lacking. In this paper, the recent SLE experiences of two PMM2-CDG patients are examined to provide clinical clues to help improve diagnosis through a clinical constellation of symptoms and a clinical definition, but also to support a neuroelectrical hypothesis as an underlying mechanism. An up-to-date literature review will help to identify evidence-based and non-evidence-based management recommendations. Presently neuropediatricians and neurologists are not capable of diagnosing stroke-like episodes in an unequivocal way, so there is still a need to perform invasive studies (to rule out other acute diseases) that may, in the end, prove unnecessary or even harmful. However, reaching a correct and early diagnosis would lead not only to avoidance of invasive tests but also to better recognition, management, and understanding of the disease itself. There is a great need for understanding of SLE that may ultimately be very informative for the detection of patients at risk, and the future development of preventive and management measures.

In Vitro Fertilisation (IVF) Associated with Preimplantation Genetic Testing for Monogenic Diseases (PGT-M) in a Romanian Carrier Couple for Congenital Disorder of Glycosylation Type Ia (CDG-Ia): A Case Report

Background: Congenital disorder of glycosylation (CDG) is a severe morphogenic and metabolic disorder that affects all of the systems of organs and is caused by a mutation of the gene PMM2, having a mortality rate of 20% during the first months of life. Results: Here we report the outcome of an in vitro fertilisation (IVF) cycle associated with preimplantation genetic testing for monogenic diseases (PGT-M) in a Romanian carrier couple for CDG type Ia with distinct mutations of the PMM2 gene. The embryonic biopsy was performed on day five of the blastocyst stage for six embryos. The amplification of the whole genome had been realized by using the PicoPLEX WGA kit. Using the Array Comparative Genomic Hybridisation technique, we detected both euploid and aneuploid embryos. The identification of the PMM2 mutation on exon 5 and exon 6 was performed for the euploid embryos through Sanger Sequencing with specific primers on ABI 3500. Of the six embryos tested, only three were euploid. One had compound heterozygosity and the remaining two were simple heterozygotes. Conclusion: PGT-M should be strongly considered for optimising embryo selection in partners with single-gene mutations in order to prevent transmission to the offspring.

Unusual Presentation of PMM2-Congenital Disorder of Glycosylation With Isolated Strokelike Episodes in a Young Girl

Congenital disorders of glycosylation (CDG) are multisystemic inherited metabolic disorders with marked phenotypic variability. The most frequent described type is PMM2-CDG (earlier known as CDG Type Ia) which presents either with pure neurologic features or with combined neurologic and systemic features. The classical presentation is characterized by varied combinations of developmental delay, hypotonia, ataxia, dysmorphism, inverted nipples, and abnormal fat distribution. Strokelike episodes and seizures are known acute complications that usually occur on a background of developmental delay, ataxia, or dysmorphism. We report here a developmentally normal young girl who presented with isolated strokelike episodes and was diagnosed to have CDG Type Ia. This condition should be kept in the differentials of unexplained strokelike episodes in children. The diagnosis has important therapeutic and prognostic implications.

Neurometabolic diseases of childhood

Metabolic diseases affecting the pediatric brain are complex conditions, the underlying mechanisms leading to structural damage are diverse and the diagnostic imaging manifestations are often non-specific; hence early, sensitive and specific diagnosis can be challenging for the radiologist. However, misdiagnosis or a delayed diagnosis can result in a devastating, irreversible injury to the developing brain. Based upon the inborn error, neurometabolic diseases can be subdivided in various groups depending on the predominantly involved tissue (e.g., white matter in leukodystrophies or leukoencephalopathies), the involved metabolic processes (e.g., organic acidurias and aminoacidopathies) and primary age of the child at presentation (e.g., neurometabolic disorders of the newborn). This manuscript summarizes these topics.

29 French adult patients with PMM2-congenital disorder of glycosylation: outcome of the classical pediatric phenotype and depiction of a late-onset phenotype

PMM2-CDG (formerly known as CDG Ia) a deficiency in phosphomannomutase, is the most frequent congenital disorder of glycosylation. The phenotype encompasses a wide range of neurological and non-neurological manifestations comprising cerebellar atrophy and intellectual deficiency. The phenotype of the disorder is well characterized in children but the long term course of the disease is unknown and the phenotype of late onset forms has not been comprehensively described. We thus retrospectively collected the clinical, biological and radiological data of 29 French PMM2-CDG patients aged 15 years or more with a proven molecular diagnosis (16 females and 13 males). In addition, thirteen of these patients were reexamined at the time of the study to obtain detailed information. 27 of the 29 patients had a typical PMM2-CDG phenotype, with infantile hypotonia, strabismus, developmental delay followed by intellectual deficiency, epilepsy, retinitis pigmentosa and/or visceral manifestations. The main health problems for these patients as teenagers and in adulthood were primary ovarian insufficiency, growth retardation, coagulation anomalies and thrombotic events, skeletal deformities and osteopenia/osteoporosis, retinitis pigmentosa, as well as peripheral neuropathy. Three patients had never walked and three lost their ability to walk. The two remaining patients had a late-onset phenotype unreported to date. All patients (n = 29) had stable cerebellar atrophy. Our findings are in line with those of previous adult PMM2-CDG cohorts and points to the need for a multidisciplinary approach to the follow up of PMM2-CDG patients to prevent late complications. Additionally, our findings add weight to the view that PMM2-CDG may be diagnosed in teenage/adult patients with cerebellar atrophy, even in the absence of intellectual deficiency or non-neurological involvement.

Thrombotic complications in patients with PMM2-CDG

Many proteins regulating coagulation, including factor IX, factor XI, Antithrombin-III, Protein C and Protein S are deficient or decreased in activity in congenital disorders of glycosylation (CDG). Because of the imbalance of coagulation and anticoagulation factors, some patients develop acute vascular events, such as thrombosis. Identifying patients with increased risk for thrombotic events could prevent serious complications and even mortality. We performed a systematic review on patients diagnosed with the most common CDG form; PMM2-CDG, reported between 1990 and 2012 in medical literature. We also evaluated our PMM2-CDG patient-cohort of 15 patients. In total, based on the availability of comprehensive clinical descriptions, 100 patients were included in the study. Patients with and without thrombotic events were compared based on the alterations of the following glycosylated coagulation and anticoagulation factors: Antithrombin-III, Protein C, Protein S, factors IX and XI. We also assessed the global hemostasis, family history and provoking events. In the group of 100 PMM2-CDG patients 14 had suffered a venous or arterial thrombotic event. Low activity of several anticoagulation factors correlated with thrombotic events. Relatively high factor IX and XI activities were not associated with thrombosis. Prolonged PT and aPTT did not seem to protect against thrombosis in patients. Surgical procedures were frequently associated with thrombotic events. Based on the association of thrombosis and surgery in PMM2-CDG we advise to avoid elective surgical procedures in PMM2-CDG patients. Easily preventable risk factors like immobility should be treated with regular physiotherapy. We suggest a yearly follow-up for Antithrombin-III and Protein C levels and parent education for early thrombotic signs in CDG.

Neurology of inherited glycosylation disorders

Congenital disorders of glycosylation comprise most of the nearly 70 genetic disorders known to be caused by impaired synthesis of glycoconjugates. The effects are expressed in most organ systems, and most involve the nervous system. Typical manifestations include structural abnormalities (eg, rapidly progressive cerebellar atrophy), myopathies (including congenital muscular dystrophies and limb-girdle dystrophies), strokes and stroke-like episodes, epileptic seizures, developmental delay, and demyelinating neuropathy. Patients can also have neurological symptoms associated with coagulopathies, immune dysfunction with or without infections, and cardiac, renal, or hepatic failure, which are common features of glycosylation disorders. The diagnosis of congenital disorder of glycosylation should be considered for any patient with multisystem disease and in those with more specific phenotypic features. Measurement of concentrations of selected glycoconjugates can be used to screen for many of these disorders, and molecular diagnosis is becoming more widely available in clinical practice. Disease-modifying treatments are available for only a few disorders, but all affected individuals benefit from early diagnosis and aggressive management.

Neonatal neuroimaging findings in inborn errors of metabolism

Individually, metabolic disorders are rare, but overall they account for a significant number of neonatal disorders affecting the central nervous system. The neonatal clinical manifestations of inborn errors of metabolism (IEMs) are characterized by nonspecific systemic symptoms that may mimic more common acute neonatal disorders like sepsis, severe heart insufficiency, or neonatal hypoxic-ischemic encephalopathy. Certain IEMs presenting in the neonatal period may also be complicated by sepsis and cardiomyopathy. Early diagnosis is mandatory to prevent death and permanent long-term neurological impairments. Although neuroimaging findings are rarely specific, they play a key role in suggesting the correct diagnosis, limiting the differential diagnosis, and may consequently allow early initiation of targeted metabolic and genetic laboratory investigations and treatment. Neuroimaging may be especially helpful to distinguish metabolic disorders from other more common causes of neonatal encephalopathy, as a newborn may present with an IEM prior to the availability of the newborn screening results. It is therefore important that neonatologists, pediatric neurologists, and pediatric neuroradiologists are familiar with the neuroimaging findings of metabolic disorders presenting in the neonatal time period.

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.

A developmental and genetic classification for midbrain-hindbrain malformations

Advances in neuroimaging, developmental biology and molecular genetics have increased the understanding of developmental disorders affecting the midbrain and hindbrain, both as isolated anomalies and as part of larger malformation syndromes. However, the understanding of these malformations and their relationships with other malformations, within the central nervous system and in the rest of the body, remains limited. A new classification system is proposed, based wherever possible, upon embryology and genetics. Proposed categories include: (i) malformations secondary to early anteroposterior and dorsoventral patterning defects, or to misspecification of mid-hindbrain germinal zones; (ii) malformations associated with later generalized developmental disorders that significantly affect the brainstem and cerebellum (and have a pathogenesis that is at least partly understood); (iii) localized brain malformations that significantly affect the brain stem and cerebellum (pathogenesis partly or largely understood, includes local proliferation, cell specification, migration and axonal guidance); and (iv) combined hypoplasia and atrophy of putative prenatal onset degenerative disorders. Pertinent embryology is discussed and the classification is justified. This classification will prove useful for both physicians who diagnose and treat patients with these disorders and for clinical scientists who wish to understand better the perturbations of developmental processes that produce them. Importantly, both the classification and its framework remain flexible enough to be easily modified when new embryologic processes are described or new malformations discovered.

Mental retardation and inborn errors of metabolism

In countries where clinical phenylketonuria is detected by newborn screening inborn errors of metabolism are rare causes of isolated mental retardation. There is no international agreement about what type of metabolic tests must be applied in patients with unspecific mental retardation. However, and although infrequent, there are a number of inborn errors of metabolism that can present in this way. Because of the high recurrence risk and the possibility of specific therapies, guidelines need to be developed and adapted to different populations. The application of a universal protocol may result in a low diagnostic performance in individual ethnic populations. Consideration of associated signs (extraneurological manifestations, psychiatric signs, autistic traits, cerebellar dysfunction, epilepsy or dysmorphic traits) greatly improves the diagnostic fulfilment.

Childhood and teenage stroke

OBJECTIVE

The purpose of this manuscript is to review the various etiologies and to discuss the therapeutic issues in childhood stroke.

METHODS

A PubMed search of literature pertaining to childhood stroke was conducted from 1983 to 2008 using specific key search words pertinent to cerebrovascular disorders in childhood.

RESULTS

The analysis of the multiple causes of childhood stroke including arterial ischemic strokes and cerebral venous thrombosis was presented. Current therapy and outcome data in childhood stroke are also discussed throughout the length of the article.

CONCLUSIONS

With increasing vigilance among physicians and improved neuroimaging modalities, the diagnosis of childhood stroke is now made earlier, with increasing frequency and greater accuracy. However, larger and well-controlled studies regarding the optimal management of childhood stroke in terms of the use of both antithrombotic drugs and anticoagulation are still needed in addition to longitudinal follow-up studies of children with stroke.

Different neuroradiological findings during two stroke-like episodes in a patient with a congenital disorder of glycosylation type Ia

Congenital disorders of glycosylation type Ia (CDG-Ia) are the most common type of CDG and are characterized by liver dysfunction, coagulation disorders, mental retardation, hypotonia, cerebellar dysfunction, polyneuropathy, seizures, and stroke-like episodes. Stroke-like episodes occur in 40-55% of cases, but their etiology is not fully understood. Although it has been stated that an epileptic process may cause the stroke-like episodes, there is no clear evidence of ischemic stroke. Here, we describe two stroke-like episodes in a patient with CDG. We performed radiological studies during each episode and obtained two distinct magnetic resonance imaging (MRI) findings: one revealed an ischemic stroke, and the other demonstrated marked edema followed by focal necrosis. This is the first direct evidence of ischemic stroke, and we report that another process may affect the etiology in the same patient.

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.

Congenital disorder of glycosylation type 1a: Three siblings with a mild neurological phenotype

We report 3 siblings (1 male and 2 female) recently diagnosed with congenital disorder of glycosylation type Ia (CDG-Ia) in their mid-20s. They experience mild mental retardation but manage to function independently in society. Their professions are library assistant, professional artistic painter and secretarial work. All three siblings have cerebellar hypoplasia and ataxia, but are able to ambulate easily. Two of the siblings have required strabismus surgical repairs. All have antithrombin III deficiency, osteoporosis, and mild dysmorphic features. Hypergonadotrophic hypogonadism was a feature of the two female siblings. A type 1 sialotransferrin pattern and phosphomannomutase (PMM) deficiency have been demonstrated. They are compound heterozygotes for R141H and L32R mutations in the PMM2 gene. While there is clinical heterogeneity in CDG-Ia, we believe that our patients are among the mildest of intellectually affected CDG-Ia patients reported to date.

Radiologic and neurophysiologic aspects of stroke-like episodes in children with congenital disorder of glycosylation type Ia

In an effort to shed light on the mechanism of hemiparetic stroke-like events experienced by patients with congenital disorder of glycosylation type Ia, we evaluated 3 children with this disorder by brain imaging studies and continuous electroencephalogram monitoring during such events. No evidence of ischemia or infarction was revealed on imaging studies and electrographic seizures or intermittent epileptiform activity was demonstrated on electrographic recordings. All 3 patients showed clinical and electrographic improvement after administration of antiepileptic medication. Epileptic phenomena can complicate the stroke-like events of patients with congenital disorder of glycosylation type Ia, and the cause of the hemiparesis may indeed be an active epileptic inhibitory process. As such, electroencephalogram monitoring is warranted, and treatment with anticonvulsant agents is indicated.

Disorders of cerebellar growth and development

PURPOSE OF REVIEW

This review summarizes for the pediatrician the current understanding of normal cerebellar and brainstem development, and then discusses selected malformations to highlight advances in the area. The impact of prematurity on cerebellar growth and development is then examined. The important insights provided by recent neuroimaging and genetic advances are reviewed.

RECENT FINDINGS

Previous areas of dispute are being addressed by advances in two major areas. Advanced neuroimaging studies during fetal and postnatal life are now providing important insights into the nature of normal and abnormal development of the brainstem and cerebellum. These powerful new techniques for defining morphology in vivo, together with major advances in genetics, are accelerating our understanding of genotype-phenotype relationships. Conversely, the ability to link early brain injury to subsequent cerebellar development has challenged previous understanding of the distinction between acquired and primary dysgenesis, presumed to be genetic in origin.

SUMMARY

The synthesis of a rational and clinically useful classification of posterior fossa malformations has been elusive. Recent developments promise to resolve ongoing disputes that have delayed progress. However, these insights into disturbed structural development demand rigorous examination of their long-term functional significance and caution before their prognostic significance is applied clinically.

Congenital disorder of glycosylation type Ia presenting as early-onset cerebellar ataxia in an adult

Congenital disorders of glycosylation (CDG) are a recently described, underrecognized group of syndromes characterized biochemically by abnormal glycosylation of serum and cellular glycoproteins. We report a previously undiagnosed adult male who presented with early-onset cerebellar ataxia in the context of mental impairment, peripheral neuropathy, retinopathy, body dysmorphism, cardiomyopathy, and hypogonadism. Newly available screening and genetic testing confirmed the diagnosis as CDG type Ia. This case emphasizes that CDG should be considered as a differential diagnosis for adults with early-onset cerebellar ataxia, particularly in those persons with the aforementioned features, and that undiagnosed cases of childhood ataxia may require reassessment now that testing is available.

Severe, fetal-onset form of olivopontocerebellar hypoplasia in three sibs: PCH type 5?

We present three siblings with a precise onset of fetal seizure-like activity who had severe olivopontocerebellar hypoplasia (OPCH) and degeneration. Autopsies at 20, 27, and 37 weeks gestation showed diffuse central nervous system volume loss that was most marked for the cerebellum and brain stem structures. Neuropathological abnormalities included dysplastic, C-shaped inferior olivary nuclei, absent or immature dentate nuclei, and cell paucity more marked for the cerebellar vermis than the hemispheres. Delayed development was seen in layer 2 of the cerebral cortex and in Purkinje cells of the cerebellum. Prenatal monitoring defined a developmental window of 16-18 weeks gestation when ultrasonic assessment of cerebellar width was used for prenatal diagnosis. We discuss our findings in the context of the differential diagnosis for infantile (O)PCH and propose a classification scheme for the pontocerebellar hypoplasias. These patients represent the earliest reported with OPCH and provide unique information regarding the developmental neuropathology of this condition.

The congenital disorders of glycosylation: a multifaceted group of syndromes

The congenital disorders of glycosylation (CDG) are a rapidly expanding group of metabolic syndromes with a wide symptomatology and severity. They all stem from deficient N-glycosylation of proteins. To date the group contains 18 different subtypes: 12 of Type I (disrupted synthesis of the lipid-linked oligosaccharide precursor) and 6 of Type II (malfunctioning trimming/processing of the protein-bound oligosaccharide). Main features of CDG involve psychomotor retardation; ataxia; seizures; retinopathy; liver fibrosis; coagulopathies; failure to thrive; dysmorphic features, including inverted nipples and subcutaneous fat pads; and strabismus. No treatment currently is available for the vast majority of these syndromes (CDG-Ib and CDG-IIc are exceptions), even though attempts to synthesize drugs for the most common subtype, CDG-Ia, have been made. In this review we will discuss the individual syndromes, with focus on their neuronal involvement, available and possible treatments, and future directions.

Skeletal dysplasia and myelopathy in congenital disorder of glycosylation type IA

We report on a boy with a congenital disorder of glycosylation (CDG) Ia and a severe narrowing of the spinal canal caused by atlantoaxial subluxation with anterior displacement of C1. C1-laminectomy improved the progressive paresis. Progressive paresis caused by spinal cord compression is a hitherto unrecognized complication in patients with CDG-Ia.

Diagnostic approach to cerebellar disease in children

We reviewed the clinical records of 51 extensively investigated pediatric patients with structural abnormalities of the cerebellum as revealed by magnetic resonance imaging (MRI). Ten had hypoplasia of the vermis, 21 had hypoplasia of the vermis and cerebellar hemispheres, 2 had pontocerebellar hypoplasia, and 18 had progressive cerebellar atrophy. A clear diagnosis was reached in 37 (72.5%). Initial characterization of the cerebellar alterations by MRI separated hypoplastic from atrophic cases and confirmed MRI as an essential preliminary means for distinguishing malformations from metabolic-degenerative conditions. However, the diagnostic possibilities are so numerous that it is not feasible to propose a standardized diagnostic protocol for pediatric patients with an altered cerebellum. Subsequent investigations should be suggested by the neuroradiologic and clinical peculiarities of each case.

Tissue distribution of the murine phosphomannomutases Pmm1 and Pmm2 during brain development

The most common type of the congenital disorders of glycosylation, CDG-Ia, is caused by mutations in the human PMM2 gene, reducing phosphomannomutase (PMM) activity. The PMM2 mutations mainly lead to neurological symptoms, while other tissues are only variably affected. Another phosphomannomutase, PMM1, is present at high levels in the brain. This raises the question why PMM1 does not compensate for the reduced PMM2 activity during CDG-Ia pathogenesis. We compared the expression profile of the murine Pmm1 and Pmm2 mRNA and protein in prenatal and postnatal mouse brain at the histological level. We observed a considerable expression of both Pmms in different regions of the embryonic and adult mouse brain. Surprisingly, the expression patterns were largely overlapping. This data indicates that expression differences on the cellular and tissue level are an unlikely explanation for the absence of functional compensation. These results suggest that Pmm1 in vivo does not exert the phosphomannomutase-like activity seen in biochemical assays, but either acts on as yet unidentified specific substrates or fulfils entirely different functions.

Glycoscience finally comes of age

To take its place alongside genomics and proteomics, glycoscience needs recognition from scientists

Metabolic mimics: the disorders of N-linked glycosylation

N-linked glycosylation is essential for normal cellular function. Defects have now been described in eighteen genes that participate in the process. All give rise to complex multisystem diseases which, with a few exceptions, primarily involve the nervous system. Frequent features of these disorders include developmental delay, ataxia, seizures, stroke-like episodes, recurrent infections, coagulopathy and dysmorphism. Most cases can be detected by screening carbohydrate-deficient transferrin, but definitive diagnosis requires enzymatic and molecular confirmation, frequently in collaboration with a research glycobiologist.

Congenital disorder of glycosylation type Ia: a clinicopathological report of a newborn infant with cerebellar pathology

Congenital disorders of glycosylation (CDG) represent a newly delineated group of inherited multisystem disorders characterized by defective glycoprotein biosynthesis. In the present study we report and discuss the clinical and neuropathological findings in a newborn with CDG type Ia (CDG-Ia). The patient presented mild dysmorphic facial features, inverted nipples, progressive generalized edema, hypertrophic cardiomyopathy, hepatosplenomegaly, muscular hypotonia and had severe hypoalbuminemia. Deficiency of phosphomannomutase (PMM)-2 activity was detected. Molecular analysis showed V231M/T237R mutations of the PMM2 gene. Muscular biopsy, disclosed myopathic alterations with myofibrillar disarray by electron microscopy. The patient died at 1 month of age of circulatory and respiratory failure. Autopsy showed liver fibrosis and renal abnormalities. Neuropathological abnormalities were mainly confined to the cerebellum. Histological and immunocytochemical examination of cerebellar tissue showed partial atrophy of cerebellar folia with severe loss of Purkinje cells, granular cell depletion and various morphological changes in the remaining Purkinje cells and their dendritic arborization. Autopsy findings confirm the complexity of the CDG-Ia syndrome, and indicate that CDG-Ia is a distinct disease entity, which can be differentiated from other neurological disorders and other types of CDG, not only clinically, but also based on unique pathological findings. The data proved useful in determining the underlying disease process associated with a defective N-glycosylation pathway.