Ana Carolina Brusius-Facchin

Severe phenotype in MPS II patients associated with a large deletion including contiguous genes

Hunter disease or mucopolysaccharidosis type II (MPS II) is an X‐linked recessive lysosomal disorder caused by the deficiency of iduronate‐2‐sulfatase, which is involved in the catabolism of the glycosaminoglycans (GAGs) heparan and dermatan sulphate. Our aim was to analyze three patients with severe Hunter syndrome that showed a total deletion of the iduronate‐2‐sulphatase (IDS) gene, after exon by exon PCR. DNA was used as a template for PCR synthesis of IDS, FRAXA, FRAXE, and DXS1113 specific amplicons. The DNA analysis for all three patients demonstrated a complete deletion of IDS, FRAXA, and FRAXE contiguous genes. We further performed SNP‐array to delineate the deletion breakpoints and to characterize the deletion extension in the different patients. The results indicated a ∼9.4 Mb deletion in Patient 1, a ∼3.9 Mb deletion of the Xq27.3–Xq28 and a ∼3.1 Mb duplication of the X q28 region in Patient 2 and a ∼41.8 Kb deletion in Patient 3. SNP‐array was shown to be important to map for deletion breakpoints. A comprehensive molecular analysis in patients with Hunter syndrome, especially in the ones presenting the severe form, is important to the understanding of the genetic determinants of the phenotype and for the genetic counseling to be provided to the families.

Are MPS II heterozygotes actually asymptomatic? A study based on clinical and biochemical data, x-inactivation analysis and imaging evaluations

For some X‐linked disorders the expressivity and penetrance in females are almost similar to those ones found in males. For mucopolysaccharidosis type II (MPS II), there are no studies in the literature trying to identify subtle signs and symptoms of this disease in heterozygotes. The objective of this study was to compare heterozygotes and non‐heterozygotes for MPS II, in order to test the hypothesis that heterozygotes may present subtle manifestations of the disease. In this observational and transversal study we collected data on 40 Brazilian women with a positive familial history for MPS II that included clinical and physical exam, karyotype, pattern of X‐inactivation, iduronate‐2‐sulfatase (IDS) activity in leukocytes and plasma, urinary glycosaminoglycans levels, computerized tomography scans (CT) of abdomen and spine, and brain magnetic resonance imaging. The Results showed the following: According to DNA analysis, 22 women were classified as heterozygote and 18 as non‐heterozygotes. We did not find any abnormality on physical examination, karyotype, or spine CT. Also the pattern of X‐inactivation was not different between the groups. Applying the Bonferronis correction, both groups were found to differ only in relation to IDS activity in plasma and in leukocyte, which were lower in heterozygotes. In our investigation we did not find any evidence of subtle clinical manifestations of MPS II in heterozygotes. Our findings suggest there is no relation between the absence of clinical signs in these women and the occurrence of a favorable skewing pattern of X‐inactivation.

Identification of a novel missense mutation in Brazilian patient with a severe form of mucopolysaccharidosis type IVA.

Mucopolysaccharidosis type IVA (MPS IVA) or Morquio syndrome type A is an autosomal recessive disease caused by deficiency of the lysosomal enzyme N-acetylgalactosamine-6-sulfatase (GALNS). We report molecular characterization of a patient who presents the new missense mutation p.C165Y in homozygosis. Bioinformatics analysis predicted this mutation as being probably pathogenic. To evaluate the possibility that this alteration was a polymorphism we tested 100 alleles and all the results were negative. These findings together with the observation that this alteration is not present in controls, suggest that it is a disease-causing mutation, which was correlated with the severe phenotype observed in our patient. We conclude that molecular analysis of the GALNS gene, in addition to enzyme assays, is important for diagnosis and contributes to the better understanding of the relationship between genotype and phenotype, which is important as enzyme replacement therapy (ERT) will soon become available and treatment decisions will have to be take in such cases.

Diagnosis and therapy options in mucopolysaccharidosis II (Hunter syndrome)

Introduction: Hunter syndrome (Mucopolysaccharidosis II, MPS II) is a lysosomal storage disease inherited as an X-linked trait. The disease is progressive, affects multiple systems and is clinically heterogeneous. Patients with the so-called ‘attenuated’ form have somatic manifestations affecting bone, joints, respiratory, cardiac, auditory and other systems. Patients with the ‘severe form’ have, in addition to the somatic manifestations, neurocognitive decline. Areas covered: Diagnosis is reached with biochemical tests (urinary glycosaminoglycans [GAGs] and enzyme assay), usually complemented with genetic analysis. Mutation identification could play a role in phenotype prediction and could help to identify carriers, which is very important in an X-linked disease. Specific treatment with enzyme replacement therapy (ERT) became available few years ago and improved significantly the natural course of the disease. However, treatment with intravenous ERT has limitations, and the possibility of alternative therapies such as hematopoietic stem cell transplantation and substrate reduction therapy with genistein is being considered. Novel therapies mainly designed to address the CNS manifestations (intrathecal ERT, ERT with fusion proteins, gene therapy and others) are also in development. Expert opinion: The combination of effective therapies with early diagnosis (newborn screening is feasible and could be available shortly) could completely change the prospect for MPS II patients in few years.

Investigation of newborns with abnormal results in a newborn screening program for four lysosomal storage diseases in Brazil

Lysosomal storage diseases (LSDs) are genetic disorders, clinically heterogeneous, mainly caused by defects in genes encoding lysosomal enzymes that degrade macromolecules. Several LSDs already have specific therapies that may improve clinical outcomes, especially if introduced early in life. With this aim, screening methods have been established and newborn screening (NBS) for some LSDs has been developed. Such programs should include additional procedures for the confirmation (or not) of the cases that had an abnormal result in the initial screening. We present here the methods and results of the additional investigation performed in four babies with positive initial screening results in a program of NBS for LSDs performed by a private laboratory in over 10,000 newborns in Brazil. The suspicion in these cases was of Mucopolysaccharidosis I - MPS I (in two babies), Pompe disease and Gaucher disease (one baby each). One case of pseudodeficiency for MPS I, 1 carrier for MPS I, 1 case of pseudodeficiency for Pompe disease and 1 carrier for Gaucher disease were identified. This report illustrates the challenges that may be encountered by NBS programs for LSDs, and the need of a comprehensive protocol for the rapid and precise investigation of the babies who have an abnormal screening result.

Extension of the molecular analysis to the promoter region of the iduronate 2-sulfatase gene reveals genomic alterations in mucopolysaccharidosis type II patients with normal coding sequence

Hunter disease or mucopolysaccharidosis type II (MPS II) is an X-linked recessive lysosomal disorder caused by the deficit of the enzyme iduronate-2-sulfatase (IDS), involved in the catabolism of the glycosaminoglycans heparan and dermatan sulfate. Our aim was to search for molecular defects in the promoter region of the IDS gene in patients with previous biochemical diagnosis of MPS II and after we sequenced the whole IDS coding region and the exon/intron boundaries without detecting any pathogenic mutations. Screening of the promoter region of four patients detected in two of them a 178 bp deletion and in the other two a single nucleotide substitution 818 bp upstream of the coding region. The latter had never been described before in MPS II patients and it turned out to be a polymorphism. Our experience suggests that MPS II patients with no mutations detected in the IDS coding region should be screened in the promoter region of the gene. Findings will hopefully help to clarify the relationship between genotype and phenotype and will be useful for the correct molecular diagnosis of Hunter patients and the identification of female carriers, the latter particularly important for genetic counseling.

Val66Met polymorphism association with serum BDNF and inflammatory biomarkers in major depression

Abstract Objectives: Current evidence supports participation of neurotrophic and inflammatory factors in the pathogenesis of major depressive disorder (MDD). Some studies reported an association between the Val66Met polymorphism (rs6265) of brain-derived neurotrophic factor (BDNF) gene with MDD and peripheral BDNF levels. However, no previous studies have examined the association of this polymorphism with inflammation. The present study assessed the association of the Val66Met polymorphism with serum levels of BDNF and inflammatory markers among depressed outpatients. Methods: All participants (n = 73) met DSM-IV criteria for a unipolar depressive episode. The serum levels of BDNF and inflammatory biomarkers (IL-2, IL-4, IL-6, IL-10, TNF-α and IFN-γ) were compared between individuals presenting with at least one Met allele (Met-carriers) and those homozygous for the Val allele. Results: In our sample (84.9% female, mean age 52.4 ± 10.3 years), 24.7% (n = 18) were Met-carriers. After Bonferroni correction, the Met allele was significantly associated with higher BDNF and lower TNF-α. These associations persisted after adjusting for potential confounders. Conclusions: The pattern of low BDNF and high inflammation in MDD may be influenced by the Val66Met polymorphism. The association of a polymorphism in the BDNF gene with inflammatory markers in addition to BDNF levels suggests an interaction between these systems.

Cardiac disease as the presenting feature of mucopolysaccharidosis type IIIA: A case report

Severe cardiac involvement is a common feature of mucopolysaccharidoses (MPS), but occurs only rarely in MPS III (Sanfilippo syndrome). We report herein a case of MPS III-A having cardiac involvement as its first manifestation. Analysis of the SGSH gene showed homozygosity for the novel mutation p.G80V. We propose that MPS disorders, including MPS III-A, should be included in the differential diagnosis of every case of cardiomyopathy presenting during the first year of life.

Elevation of glycosaminoglycans in the amniotic fluid of a fetus with mucopolysaccharidosis VII

The aim of this study was to quantify glycosaminoglycans (GAGs) in amniotic fluid (AF) from an MPS VII fetus compared with age‐matched fetuses obtained from normal pregnancies.

Recent advances in molecular testing to improve early diagnosis in children with mucopolysaccharidoses

ABSTRACT Introduction: The mucopolysaccharidoses (MPS) are a group of lysosomal storage disorders with high phenotypic and genotypic heterogeneity, making precise diagnosis challenging. Although enzyme activity assay is considered the gold standard for the diagnosis of these disorders, molecular testing can greatly refine this task. New methods for rapid detection of variants are useful to reduce the ‘diagnostic odyssey’ faced by patients and their family, to lead to appropriate genetic counseling and to select the most appropriate therapy for each case. Areas covered: We review and discuss the advantages, disadvantages and limitations of the modern technologies in the field of molecular diagnosis of MPS, presenting our own experience. Expert commentary: While current molecular genetics testing for MPS mostly relies on PCR and Sanger sequencing, promising alternative techniques have emerged over the last few years, and its application into routine clinical practice is gaining momentum.