Examining the Distribution and Impact of Single-Nucleotide Polymorphisms in the Capsular Locus of Streptococcus pneumoniae Serotype 19A.

Streptococcus pneumoniae serotype 19A prevalence has increased after the implementation of the PCV7 and PCV10 vaccines. In this study, we have provided, with high accuracy, the genetic diversity of the 19A serotype in a cohort of Dutch invasive pneumococcal disease patients and asymptomatic carriers obtained in the period from 2004 to 2016. The whole genomes of the 338 pneumococcal isolates in this cohort were sequenced and their capsule (cps) loci compared to examine their diversity and determine the impact on the production of capsular polysaccharide (CPS) sugar precursors and CPS shedding. We discovered 79 types with a unique cps locus sequence. Most variation was observed in the rmlB and rmlD genes of the TDP-Rha synthesis pathway and in the wzg gene, which is of unknown function. Interestingly, gene variation in the cps locus was conserved in multiple alleles. Using RmlB and RmlD protein models, we predict that enzymatic function is not affected by the single-nucleotide polymorphisms as identified. To determine if RmlB and RmlD function was affected, we analyzed nucleotide sugar levels using ultrahigh-performance liquid chromatography-mass spectrometry (UHPLC-MS). CPS precursors differed between 19A cps locus subtypes, including TDP-Rha, but no clear correlation was observed. Also, significant differences in multiple nucleotide sugar levels were observed between phylogenetically branched groups. Because of indications of a role for Wzg in capsule shedding, we analyzed if this was affected. No clear indication of a direct role in shedding was found. We thus describe genotypic variety in rmlB, rmlD, and wzg in serotype 19A in the Netherlands, for which we have not discovered an associated phenotype.

Mimicking Behçet's disease: GM-CSF gain of function mutation in a family suffering from a Behçet's disease-like disorder marked by extreme pathergy.

Behçet's disease (BD) is an inflammatory disease mainly affecting men along the ancient Silk Route. In the present study we describe a Dutch family suffering from BD-like disease with extreme pathergic responses, but without systemic inflammation. Genetic assessment revealed a combination of the human leukocyte antigen (HLA)-B*51 risk-allele together with a rare heterozygous variant in the CSF2 gene (c.130A>C, p.N44H) encoding for granulocyte-macrophage colony-stimulating factor (GM-CSF) found by whole exome sequencing. We utilized an over-expression vector system in a human hepatocyte cell line to produce the aberrant variant of GM-CSF. Biological activity of the protein was measured by signal transducer and activator of transcription 5 (STAT-5) phosphorylation, a downstream molecule of the GM-CSF receptor, in wild-type peripheral mononuclear cells (PBMCs) using flow cytometry. Increased STAT-5 phosphorylation was observed in response to mutated GM-CSF when compared to the wild-type or recombinant protein. CSF2 p.N44H results in disruption of one of the protein's two N-glycosylation sites. Enzymatically deglycosylated wild-type GM-CSF also enhanced STAT-5 phosphorylation. The patient responded well to anti-tumor necrosis factor (TNF)-α treatment, which may be linked to the capacity of TNF-α to induce GM-CSF in phorbol 12-myristate 13-acetate (PMA)-treated PBMCs, while GM-CSF itself only induced dose-dependent interleukin (IL)-1Ra production. The identified CSF2 pathway could provide novel insights into the pathergic response of BD-like disease and offer new opportunities for personalized treatment.

Oral ribose supplementation in dystroglycanopathy: A single case study.

Three forms of muscular dystrophy-dystroglycanopathies are linked to the ribitol pathway. These include mutations in the isoprenoid synthase domain-containing protein (ISPD), fukutin-related protein (FKRP), and fukutin (FKTN) genes. The aforementioned enzymes are required for generation of the ribitol phosphate linkage in the O-glycan of alpha-dystroglycan. Mild cases of dystroglycanopathy present with slowly progressive muscle weakness, while in severe cases the eyes and brain are also involved. Previous research showed that ribose increased the intracellular concentrations of cytidine diphosphate-ribitol (CDP-ribitol) and had a therapeutic effect. Here, we report the safety and effects of oral ribose supplementation during 6 months in a patient with limb girdle muscular dystrophy type 2I (LGMD2I) due to a homozygous FKRP mutation. Ribose was well tolerated in doses of 9 g or 18 g/day. Supplementation with 18 g of ribose resulted in a decrease of creatine kinase levels of 70%. Moreover, metabolomics showed a significant increase in CDP-ribitol levels with 18 g of ribose supplementation (p < 0.001). Although objective improvement in clinical and patient-reported outcome measures was not observed, the patient reported subjective improvement of muscle strength, fatigue, and pain. This case study indicates that ribose supplementation in patients with dystroglycanopathy is safe and highlights the importance for future studies regarding its potential effects.

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.

Clinical and diagnostic approach in unsolved CDG patients with a type 2 transferrin pattern.

Dysmorphic features, multisystem disease, and central nervous system involvement are common symptoms in congenital disorders of glycosylation, including several recently discovered Golgi-related glycosylation defects. In search for discriminative features, we assessed eleven children suspected with a Golgi-related inborn error of glycosylation. We evaluated all genetically unsolved patients, diagnosed with a type 2 transferrin isofocusing pattern in the period of 1999-2009. By combining biochemical results with characteristic clinical symptoms, we used a diagnostic flow chart to approach the underlying defect in patients with congenital disorders of glycosylation-IIx. According to specific symptoms and laboratory results, we initiated additional, targeted biochemical and genetic studies. We found a distinctive spectrum of congenital disorders of glycosylation type 2-associated anomalies including sudden hearing loss, brain malformations, wrinkled skin, and epilepsy in combination with skeletal dysplasia, dilated cardiomyopathy, sudden cardiac arrest, abnormal copper and iron metabolism, and endocrine abnormalities in our patients. One patient with severe cortical malformations and mild skin abnormalities was diagnosed with a known genetic syndrome, due to an ATP6V0A2 defect. Here, we present unique congenital disorders of glycosylation type 2-associated anomalies, including both ATPase-related and unrelated cutis laxa and sensorineural hearing loss, a recently recognized symptom of congenital disorders of glycosylation. Based on our findings, we recommend clinicians to consider congenital disorders of glycosylation in patients with cardiac rhythm disorders, spondylodysplasia and biochemical abnormalities of the copper and iron metabolism even in absence of intellectual disability.

New cases of adult-onset Sandhoff disease with a cerebellar or lower motor neuron phenotype.

Sandhoff disease is a lipid-storage disorder caused by a defect in ganglioside metabolism. It is caused by a lack of functional N-acetyl-beta-d-glucosaminidase A and B due to mutations in the HEXB gene. Typical, early-onset Sandhoff disease presents before 9 months of age with progressive psychomotor retardation and early death. A late-onset form of Sandhoff disease is rare, and its symptoms are heterogeneous. As drug trials that aim to intervene in the disease mechanism are emerging, the recognition and identification of Sandhoff disease patients-particularly those with atypical phenotypes-are becoming more important. The authors describe six new late-onset Sandhoff cases demonstrating cerebellar ataxia or lower motor neuron (LMN) involvement combined with, mostly subclinical, neuropathy. Two different mutations were found: IVS 12-26 G/A and c.1514G-->A. In patients with either progressive cerebellar ataxia or LMN disease in the setting of a possibly recessive disorder, Sandhoff disease should be suspected, even when the onset age is over 45 years.

Sanfilippo B in an elderly female psychiatric patient: a rare but relevant diagnosis in presenile dementia.

OBJECTIVE: Sanfilippo B is a rare autosomal recessive mucopolysaccharidosis (MPS IIIB) caused by a deficiency of N-acetyl-alpha-D-glucosaminidase (NAGLU). METHOD: A mild mentally retarded elderly female patient is described with a slowly progressive dementia who had given birth to a daughter who developed normally. RESULTS: Metabolic screening revealed an enhanced concentration of heparan sulfate in urine. Enzymatic assay demonstrated deficiency of N-acetyl-alpha-D-glucosaminidase. Mutations in the NAGLU gene were found. One mentally retarded and hospitalized elder brother was also found to have MPS IIIB, whereas a second brother, who had died earlier, is suspected to have had the same metabolic disorder. Prior to the development of dementia, both the patient and her brother showed autistic like features, signs of ideomotor apraxia and weakness in verbal comprehension. CONCLUSION: Screening for metabolic disorders, in particular MPSes, should always be considered in patients with a history of mental deficit and dementia or progressive functional decline.

Clinical features, lectin staining, and a novel GNE frameshift mutation in hereditary inclusion body myopathy.

We present a comprehensive report of two siblings with hereditary inclusion body myopathy (HIBM). The clinical features and histological characteristics of the muscle biopsies showed the typical pattern of predominantly distal vacuolar myopathy with quadriceps sparing. This was confirmed by muscle MRI. PNA lectin staining showed an increased signal at the sarcolemma in patient muscle sections compared to control muscle, indicating reduced sialylation of glycoconjugates. Mutation analysis revealed compound heterozygous mutations in the GNE gene, encoding the key enzyme in sialic acid synthesis UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase: a missense mutation (c.2086G > A; p.V696M) previously described in HIBM patients of Indian origin, and a novel frame shift mutation (c.1295delA; p.K432RfsX17) leading to a premature stopcodon. These findings confirmed the diagnosis of HIBM on the histological, molecular and biochemical level.

Substrate deprivation therapy in juvenile Sandhoff disease.

Substrate deprivation therapy has been successfully applied in a number of lysosomal storage diseases, such as Gaucher disease. So far only limited experience is available in Sandhoff disease. We initiated substrate deprivation therapy in one male patient, who initially presented at the age of 3.5 years with epilepsy and regression in motor skills and speech development. Juvenile Sandhoff disease was diagnosed on the basis of a decreased hexosaminidase activity in leukocytes and a homozygous HEXB gene mutation. After the epilepsy was controlled, the clinical course remained stable for years, defined by a mild proximal myopathy and stable mental retardation. At 14 years of age the patient experienced a second episode with progressively worsening general condition with diminishing muscle power and progressive ataxia. Treatment was started with the N-alkylated imino sugar miglustat, inhibiting the glucosylceramide synthase, an essential enzyme for the synthesis of glycosphingolipids. Diarrhoea was treated with lactose restriction. We performed detailed biochemical investigations, motor and mental development analysis, brain imaging, organ function studies and quality of life score prior to and at different time points after start of the treatment. Two years after the initiation of therapy the patient has a stable neurological picture without further regression in his motor development, ataxia or intelligence. There is a subjective improvement in the fine motor skills and walking up the stairs but no change in the quality of life score. Under treatment with miglustat the clinical course in our patient with Sandhoff disease did not further deteriorate.

Relative quantification of plasma N-glycans in type II congenital disorder of glycosylation patients by mass spectrometry.

BACKGROUND: Type II Congenital Disorders of Glycosylation (CDG-II) are a group of diseases with challenging diagnostics characterized by defects in the processing of glycans in the Golgi apparatus. Mass Spectrometry (MS) has been a valuable tool in the definition of CDG-II subtypes. While some CDG-II subtypes are associated with specific N-glycan structures, others only produce changes in relative levels, reinforcing the demand for quantification methods. METHODS: Plasma samples from control individuals were pooled, derivatized with deuterated iodomethane (I-CD3), and used as internal standards for controls and patients whose glycans were derivatized with iodomethane (I-CH3), followed by MALDI MS, LC-MS and -MS/MS analyses. RESULTS: Total N-glycans from fifteen CDG-II patients were evaluated, and 4 cases with molecular diagnosis were considered in detail: 2ATP6V0A2-CDG siblings, and 2 MAN1B1-CDG patients, one of them carrying a previously undescribed p.Gly536Val mutation. CONCLUSIONS: Our methodology offers a feasible alternative to the current methods for CDG-II diagnosis by MS, which quantify glycan structures as fractions of the total summed signal across a mass spectrum, a strategy that lowers the variability of minor components. Moreover, given its sensitivity for less concentrated yet biologically relevant structures, it might assist the uncovering of novel diagnostic glycans in other CDG-II subtypes.

Defining the phenotype in an autosomal recessive cutis laxa syndrome with a combined congenital defect of glycosylation.

Autosomal recessive cutis laxa is a genetically heterogeneous condition. Its molecular basis is largely unknown. Recently, a combined disorder of N- and O-linked glycosylation was described in children with congenital cutis laxa in association with severe central nervous system involvement, brain migration defects, seizures and hearing loss. We report on seven additional patients with similar clinical features in combination with congenital disorder of glycosylation type IIx. On the basis of phenotype in 10 patients, we define an autosomal recessive cutis laxa syndrome. The patients have a complex phenotype of neonatal cutis laxa, transient feeding intolerance, late closure of the fontanel, characteristic facial features including down-slanting palpebral fissures, short nose and small mouth, and developmental delay. There is a variable degree of the central nervous system involvement and variable systemic presentation. The biochemical analysis using transferrin isoelectric focusing gives false negative results in some of the youngest patients. Analysis of the apolipoprotein C-III isoelectric focusing, however, is diagnostic in all cases.

Congenital disorder of glycosylation type Ix: review of clinical spectrum and diagnostic steps.

Congenital disorder of glycosylation type I (CDG I) represent a rapidly growing group of inherited multisystem disorders with 13 genetically established subtypes (CDG Ia to CDG Im), and a high number of biochemically unresolved cases (CDG Ix). Further diagnostic effort and prognosis counselling are very challenging in these children. In the current study, we reviewed the clinical records of 10 CDG Ix patients and compared the data with 13 CDG Ix patients published in the literature in search for specific symptoms to create clinical subgroups. The most frequent findings were rather nonspecific, including developmental delay and axial hypotonia. Several features were found that are uncommon in CDG syndrome, such as elevated creatine kinase or arthrogryposis. Distinct ophthalmological abnormalities were observed including optic nerve atrophy, cataract and glaucoma. Two subgroups could be established: one with a pure neurological presentation and the other with a neurological-multivisceral form. The first group had a significantly better prognosis. The unique presentation of microcephaly, seizures, ascites, hepatomegaly, nephrotic syndrome and severe developmental delay was observed in one child diagnosed with CDG Ik. Establishing clinical subgroups and increasing the number of patients within the subgroups may lead the way towards the genetic defect in children with a so far unsolved type of the congenital disorders of glycosylation. Raising awareness for less common, non-CDG specific clinical features such as congenital joint contractures, movement disorders or ophthalmological anomalies will encourage clinicians to think of CDG in its more unusual presentation. Clinical grouping also helps to determine the prognosis and provide better counselling for the families.

Congenital disorder of glycosylation type Ia presenting with hydrops fetalis.

There is a growing awareness that inborn errors of metabolism can be a cause of non-immune hydrops fetalis. The association between congenital disorders of glycosylation (CDG) and hydrops fetalis has been based on one case report concerning two sibs with hydrops fetalis and CDG-Ik. Since then two patients with hydrops-like features and CDG-Ia have been reported. Two more unrelated patients with CDG-Ia who presented with hydrops fetalis are reported here, providing definite evidence that non-immune hydrops fetalis can be caused by CDG-Ia. The presence of congenital thrombocytopenia and high ferritin levels in both patients was remarkable. These might be common features in this severe form of CDG. Both patients had one severe mutation in the phosphomannomutase 2 gene, probably fully inactivating the enzyme, and one milder mutation with residual activity, as had the patients reported in literature. The presence of one severe mutation might be required for the development of hydrops fetalis. CDG-Ia should be considered in the differential diagnosis of hydrops fetalis and analysis of PMM activity in chorionic villi or amniocytes should also be considered.

Recurrent thrombo-embolism in a child with a congenital disorder of glycosylation (CDG) type Ib and treatment with mannose.

Thrombosis is a multifactorial disorder. Congenital disorders of glycosylation (CDG) are one of the known risk factors for its occurrence. These disorders result in glycosylation defects of glycoproteins, including those of the (anti-)coagulation system. CDG-Ib can specifically be treated with mannose, as illustrated by the case of a 4-year-old girl in whom deep venous thrombosis was the presenting symptom after a common viral infection. The diagnosis was made after recurrent episodes of thrombo-embolism and consumptive coagulopathy. After treatment with mannose no such episodes recurred. The pathophysiology of CDG as a risk factor for thrombotic disease is discussed.

Cerebellar ataxia and congenital disorder of glycosylation Ia (CDG-Ia) with normal routine CDG screening.

Cerebellar ataxia can have many genetic causes among which are the congenital disorders of glycosylation type I (CDG-I). In this group of disorders, a multisystem phenotype is generally observed including the involvement of many organs, the endocrine, hematologic and central nervous systems. A few cases of CDG-Ia have been reported with a milder presentation, namely cerebellar hypoplasia as an isolated abnormality. To identify patients with a glycosylation disorder, isofocusing of plasma transferrin is routinely performed. Here, we describe two CDG-Ia patients,who presented with mainly ataxia and cerebellar hypoplasia and with a normal or only slightly abnormal transferrin isofocusing result. Surprisingly, the activity of the corresponding enzyme phosphomannomutase was clearly deficient in both leucocytes and fibroblasts. Therefore, in patients presenting with apparently recessive inherited ataxia caused by cerebellar hypoplasia and an unknown genetic aetiology after proper diagnostic work-up, we recommend the measurement of phosphomannomutase activity when transferrin isofocusing is normal or inconclusive.

Transferrin hypoglycosylation in hereditary fructose intolerance: using the clues and avoiding the pitfalls.

Hereditary fructose intolerance (HFI) is caused by a deficiency of aldolase B due to mutations of the ALDOB gene. The disease poses diagnostic problems because of unspecific clinical manifestations. We report three cases of HFI all of whom had a chronic disease with neurological, nephrological or gastroenterological symptoms, whereas nutritional fructose intolerance, the pathognomonic sign of HFI, was apparent only in retrospect. In all patients a hypoglycosylated pattern of transferrin isoforms was found but was misinterpreted as a sign of CDG Ix. The correct diagnosis was achieved with marked delay (26, 36 and 24 months, respectively) by sequencing of the ALDOB gene two common mutations were identified on both alleles or on one (A150P/A175D, A150P/-, and A150P/A175D). The diagnosis was further supported by normalization of transferrin isoforms on a fructose-free diet. Data available in two patients showed that following the fructose restriction the type I pattern of carbohydrate-deficient transferrin detectable on fructose-containing diet disappeared after 3-4 weeks. These cases illustrate that in the first years of life HFI may show misleading variability in clinical presentation and that protein glycosylation analysis such as transferrin isofocusing may give important diagnostic clues. However, care should be taken not to misinterpret the abnormal results as CDG Ix as well as to remember that a normal profile does not exclude HFI due to the possibility of spontaneous fructose restriction in the diet. The presented data also emphasize the usefulness of ALDOB mutation screening for diagnosis of HFI.

PGM1 deficiency: Substrate use during exercise and effect of treatment with galactose.

Mutations in PGM1 (phosphoglucomutase 1) cause Glycogen Storage Disease type XIV, which is also a congenital disorder of protein N-glycosylation. It presents throughout life as myopathy with additional systemic symptoms. We report the effect of oral galactose treatment during five months in a patient with biochemically and genetically confirmed PGM1 deficiency. The 12-minute-walking distance increased by 225 m (65%) and transferrin glycosylation was restored to near-normal levels. The exercise assessments showed a severe exercise intolerance due to a block in skeletal muscle glycogenolytic capacity and that galactose treatment tended to normalize skeletal muscle substrate use from fat to carbohydrates during exercise.

A homozygous DPM3 mutation in a patient with alpha-dystroglycan-related limb girdle muscular dystrophy.

Defects of O-linked glycosylation of alpha-dystroglycan cause a wide spectrum of muscular dystrophies ranging from severe congenital muscular dystrophy associated with abnormal brain and eye development to mild limb girdle muscular dystrophy. We report a female patient who developed isolated pelvic girdle muscle weakness and wasting, which became symptomatic at age 42. Exome sequencing uncovered a homozygous c.131T > G (p.Leu44Pro) substitution in DPM3, encoding dolichol-P-mannose (DPM) synthase subunit 3, leading to a 50% reduction of enzymatic activity. Decreased availability of DPM as an essential donor substrate for protein O-mannosyltransferase (POMT) 1 and 2 explains defective skeletal muscle alpha-dystroglycan O-glycosylation. Our findings show that DPM3 mutations may lead to an isolated and mild limb girdle muscular dystrophy phenotype without cardiomyopathy.

Hypoglycosylation is a common finding in antithrombin deficiency in the absence of a SERPINC1 gene defect.

UNLABELLED: Essentials We investigated the molecular base of antithrombin deficiency in cases without SERPINC1 defects. 27% of cases presented hypoglycosylation, transient in 62% and not restricted to antithrombin. Variations in genes involved in N-glycosylation underline this phenotype. These results support a new form of thrombophilia. Click here to listen to Dr Huntington's perspective on thrombin inhibition by the serpins SUMMARY: Background Since the discovery of antithrombin deficiency, 50 years ago, few new thrombophilic defects have been identified, all with weaker risk of thrombosis than antithrombin deficiency. Objective To identify new thrombophilic mechanisms. Patients/methods We studied 30 patients with antithrombin deficiency but no defects in the gene encoding this key anticoagulant (SERPINC1). Results A high proportion of these patients (8/30: 27%) had increased hypoglycosylated forms of antithrombin. All N-glycoproteins tested in these patients (α1-antitrypsin, FXI and transferrin) had electrophoretic, HPLC and Q-TOF patterns indistinguishable from those of the congenital disorders of glycosylation (rare recessive multisystem disorders). However, all except one had no mental disability. Moreover, intermittent antithrombin deficiency and hypoglycosylation was recorded in five out of these eight patients, all associated with moderate alcohol intake. Genetic analysis, including whole exome sequencing, revealed mutations in different genes involved in the N-glycosylation pathway. Conclusions Our study provides substantial and novel mechanistic insights into two disease processes, with potential implications for diagnosis and clinical care. An aberrant N-glycosylation causing a recessive or transient antithrombin deficiency is a new form of thrombophilia. Our data suggest that congenital disorders of glycosylation are probably underestimated, especially in cases with thrombosis as the main or only clinical manifestation.