Dataset Information

AB082. Phenotype and genotype of Vietnamese patients with mucopolysaccharidosis II: first case series report

ABSTRACT:

Background and objective

Mucopolysaccharidosis II (MPS II, Hunter syndrome, OMIM 309900) is an X-linked lysosomal storage disorder. MPS II is caused by a deficiency in the enzyme iduronate-2 sulfatase (I2S), leading to the accumulation of the glycosaminoglycans (GAGs) dermatan sulfate and heparan sulfate in lysosomes. Excessive storage of these GAGs causes a variety of clinical manifestations: coarse facies, hearing loss, cardiac valve disease, restrictive and obstructive airway disease, hepatosplenomegaly, skeletal abnormalities, joint contractures, short stature. The study aims to describe clinical characteristics and to identify mutations in the IDS gene in Vietnamese patients with MPS II.

Methods

This case series report including 18 cases with MPS II diagnosed and treated at the National Hospital of Pediatric, Vietnam from December 2012 to May 2015. We describe clinical manifestations, radiological, biochemical evaluations and identified mutations of IDS gene of the patients confirmed by enzyme assay. Nine exons and their intronic boundaries of the IDS gene were sequenced using genomic DNA from the patient. Subsequently, to identify the recombination event with pseudogene, PCR analysis was carried out.

Results

Mean age of diagnosis was 8.2±5.9 years. The clinical symptoms included coarsened facial features (100%); mental retardation and joint stiffness (88.89%); bone deformation (66.67%); hepatomegaly (33.33%); valvular heart disease (22.22%); hearing loss (16.67%); obstructive airway disease (100%). Mutations of IDS gene were identified in 14/18 of cases (77.8%) including six cases (33.33%) had recombination event. Three reported causative mutations were identified: c.120-122del (p.L41del); c.1001A > G (p.D334G); c.879G > C (p.Q293H); and five novel one were identified in this study: c.166dup (p.D56Gfs*2); c.1124-1128dup (p.L377Gfs*10); c.473del (p.Y158fs); c.814C > T (p.Q272*) and c.1048A > T (p.N350Y).

Conclusions

Description of clinical characteristics to predict severity of phenotype and identification of mutations in the IDS gene help in making diagnosis and suitable treatment decision.

SUBMITTER: Hang L

PROVIDER: S-EPMC4563500 | biostudies-literature | 2015 Sep

REPOSITORIES: biostudies-literature

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Project description:BACKGROUND:Hunter syndrome (mucopolysaccharidosis type II) is a recessive X-linked disorder due to mutations in the iduronate 2-sulfatase (IDS) gene. The IDS gene encodes a lysosomal enzyme, iduronate 2-sulfatase. The disease occurs almost exclusively in males. However, in the literature, 12 cases of the disease in females are known due to structural anomalies, a non-random chromosome X inactivation or chromosome X monosomy. The purpose of this article is to demonstrate a rare case of Hunter syndrome in a girl caused by a mutation in the IDS gene inherited from the mother and the presence of chromosome X of paternal origin, partially deleted in the long arm region - 46,X,del(X)(q22.1). CASE PRESENTATION:Girl M., 4?years old, entered the hospital with growth retardation, pain in the lower limbs, and joint stiffness, noted from the age of 18?months. After the karyotype analysis, which revealed a partial deletion of the long arm of chromosome X - 46, X, del (X) (q 22.1), Turner syndrome was diagnosed. However, due to the hurler-like facial phenotype, Hurler syndrome or type I mucopolysaccharidosis (MPS) was suspected. The study of lysosomal enzymes showed normal alpha-L-iduronidase activity and a sharp decrease in the activity of iduronate sulfatase in the blood: 0.001??M/l/h, at a rate of 2.5-50??M/l/h. Molecular genetic analysis revealed a hemizygous deletion in the IDS gene, which was not registered in the international Human Gene Mutation Database (HGMD) professional. This deletion was not detected in the girl's father, but was detected in her mother in the heterozygous state. CONCLUSIONS:Thus, the girl confirmed comorbidity - Turner syndrome with a partial deletion of the long arm of chromosome X of paternal origin, affecting the Xq28 region (localization of the IDS gene), and Hunter syndrome due to a deletion of the IDS gene inherited from the mother. The structural defect of chromosome X in the girl confirmed the hemizygous state due to the mutation in the IDS gene, which has led to the formation of the clinical phenotype of Hunter syndrome.