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:PurposeAchromatopsia is a rare stationary retinal disorder that primarily affects the cone photoreceptors. Individuals with achromatopsia present with photophobia, nystagmus, reduced visual acuity (VA), and color blindness. Multiple genes responsible for achromatopsia have been identified (e.g. cyclic nucleotide-gated channel subunit alpha 3 [CNGA3] and activating transcription factor 6). Studies have assessed the role of gene therapy in achromatopsia. Therefore, for treatment and prevention, the identification of phenotypes and genotypes is crucial. Here, we described the clinical manifestations and genetic mutations associated with achromatopsia in patients from Saudi Arabia.MethodsThis case series study included 15 patients with clinical presentations, suggestive of achromatopsia, who underwent ophthalmological and systemic evaluations. Patients with typical achromatopsia phenotype underwent genetic evaluation using whole-exome testing.ResultsAll patients had nystagmus (n = 15) and 93.3% had photophobia (n = 14). In addition, all patients (n = 15) had poor VA. Hyperopia with astigmatism was observed in 93.3% (n = 14) and complete color blindness in 93.3% of the patients (n = 14). In the context of family history, both parents of all patients (n = 15) were genetic carriers, with a high consanguinity rate (82%, n = 9 families). Electroretinography showed cone dysfunction with normal rods in 66.7% (n = 10) and both cone-rod dysfunction in 33.3% (n = 5) patients. Regarding the genotypic features, 93% of patients had variants in CNGA3 (n = 14) categorized as pathogenic Class 1 (86.7%, n = 13). Further, 66.7% (n = 10) of patients also harbored the c.661C>T DNA variant. Further, the patients were homozygous for these mutations. Three other variants were also identified: c.1768G>A (13.3%, n = 2), c.830G>A (6.6%, n = 1), and c. 822G >T (6.6%, n = 1).ConclusionConsanguinity and belonging to the same tribe are major risk factors for disease inheritance. The most common genotype was CNGA3 with the c.661C>T DNA variant. We recommend raising awareness among families and providing genetic counseling for this highly debilitating disease.

Project description:BackgroundHunter 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 presentationGirl 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 μM/l/h, at a rate of 2.5-50 μM/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.ConclusionsThus, 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.