Neurophysiology of hearing in patients with mucopolysaccharidosis type IV

Background

Hearing impairment is a common problem in patients with mucopolysaccharidosis IV (MPS IV) throughout their life. Many of the adult patients with MPS IV exhibit permanent or severe hearing loss. However, there has been no systematic review of detailed audiological test results in MPS IV.

Challenges in the Management of Mucopolysaccharidosis Type II (Hunter's Syndrome) in a Developing Country: a Case Report

Background

Mucopolysaccharidosis type II (Hunter''s syndrome) is an X-linked chromosomal storage disorder due to deficiency of the lysosomal enzyme iduronate-2-sulfatase with patients rarely living till adulthood. Failure to identify patients early could contribute to an increased morbidity as identified in this case report.

Case Details

An eight year old patient with Hunter''s syndrome identified five years after disease onset with severe cardiovascular complications exemplifies the challenges faced in resource-limited countries towards making diagnosis and treatment of rare conditions. Elevated urinary glycosaminoglycans levels or a strong clinical suspicion of Hunter''s syndrome, as identified in the index case, is a prerequisite for enzyme activity testing. Urinary mucopolysaccharide(MPS) level was 69.6mg/mmol(normal range is 0.0 – 11.6mg/mmol), and the confirming MPS electrophoresis analysis showed elevated heparan sulphate in the urine sample. Enzyme activity testing, with absent or very low iduronate-2-sulfatase activity, is diagnostic. However, the scarce availability and high cost of these tests is another constraint in making a diagnosis.

Conclusion

Identification and management of mucopolysaccharidosis type II pose a problem in resource-constrained countries due to late presentation, lack of facility for diagnosis and treatment, cost and expertise required for the management.     

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Objective: To develop and field-test a physical performance measure (MPS-PPM) for individuals with Mucopolysaccharidosis I (MPS I), a rare genetic disorder. Methods: Motor performance and endurance items were developed based on literature review, clinician feedback, feasibility, and equipment and training needs. A standardized testing protocol and scoring rules were created. The MPS-PPM includes: Arm Function (7 items), Leg Function (5 items), and Endurance (2 items). Pilot data were collected for 10 subjects (ages 5–29 years). We calculated Spearman's rho correlations between age, severity and summary z-scores on the MPS-PPM. Results: Subjects had variable presentations, as correlations among the three sub-test scores were not significant. Increasing age was related to greater severity in physical performance (r = 0.72, p<0.05) and lower scores on the Leg Function (r = ?0.67, p<0.05) and Endurance (r = ?0.65, p<0.05) sub-tests. The MPS-PPM was sensitive to detecting physical performance deficits, as six subjects could not complete the full battery of Arm Function items and eight subjects were unable to complete all Leg Function items. Subjects walked more slowly and expended more energy than typically developing peers. Conclusions: Individuals with MPS I have difficulty with arm and leg function and reduced endurance. The MPS-PPM is a clinically feasible measure that detects limitations in physical performance and may have potential to quantify changes in function following intervention.     

不同筛查方法对粘多糖贮积症的筛查效能分析

目的：探讨不同筛查方法对粘多糖贮积症（MPS）的筛查效能。方法回顾2011年1月至2013年12月于本院儿科及遗传咨询门诊就诊的72例可疑患儿的尿粘多糖筛查结果（本研究遵循的程序符合四川大学华西第二医院人体试验委员会所制定的伦理学标准,得到该委员会批准,并征得受试对象本人的知情同意,与之签署临床研究知情同意书）。同时采用甲苯胺蓝显色实验法及溴化十六烷基三甲胺沉淀实验法对疑似 MP S患儿进行尿液粘多糖筛查。结果显色实验法结果呈阳性患儿为25例,阳性筛查效能为72.22%（13/18）,阴性筛查效能为100%（10/10）;沉淀实验法示36例患儿结果呈阳性,阳性筛查效能为42.86%（6/14）,阴性筛查效能为50%（7/14）。两种方法的阳性和阴性筛查效能比较,差异均有统计学意义（P〈0.05）。结论甲苯胺蓝显色实验法是一种简单、快捷、灵敏的 MPS 筛查方法,值得在广大基层医院推广使用,有利于提高该病检出率。     

黏多糖贮积症Ⅰ型二例基因突变检测及产前诊断

目的 对黏多糖贮积症Ⅰ型病例进行基因检测,对再孕母亲进行产前诊断.方法 用酶学检测方法 确诊2例黏多糖贮积症Ⅰ型先证者;采用PCR扩增技术结合序列分析的方法,检测2例先证者血液及其再孕母亲羊水细胞中IDUA基因外显子及其两侧内含子.结果 在2例经酶学检测确诊的先证者中共检测出4种基因突变:p.L238R、c.883InsC、c.531InsT、p.L346R,2种为插入突变,2种为错义突变.在先证者1母亲羊水细胞IDUA基因中未发现致病基因突变,羊水细胞中IDUA酶活性为9.0 nmol/(h·mg蛋白);在先证者2母亲羊水细胞IDUA基因中检测到与先证者相同的两个致病突变,羊水细胞中IDUA酶活性为0.5 mol/(h·mg蛋白).结论 从黏多糖贮积症Ⅰ型先证者发现的4种突变中,p.L346R为已知突变,p.L238R,c.883InsC,c.531InsT为首次发现的新突变.胎儿1未获得与先证者相同致病基因,为正常胎儿.胎儿2获得与先证者相同致病基因,为受累胎儿.产前基因诊断结果 与酶学产前诊断结果 相符合.

Abstract：

Objectiye Mucopolysaccharidosis type Ⅰ(MPS Ⅰ; MIM# 252800)is an autosomal recessive disease that results from the deficiency in the lysosomal enzyme α-L-iduronidase(IDUA).IDUA is one of the enzymes involved in degradation of glycosaminoglycans heparan sulphate and dermatan sulphate.The deficiency of IDUA leads to widespread accumulation of partially degraded mucopolysaccharides inside lysosomes,resulting in progressive cellular and multiorgan dysfunction. Up to now there is no definitely effective treatment for this disorder,therefore it is important to provide an accurate genetic diagnosis and prenatal diagnosis for the MPS Ⅰ families.This study was conducted to detect IDUA gene mutation in patients with MPS Ⅰ and make a definite diagnosis of homozygote or heterozygote and make first trimester prenatal diagnosis.Method The 2 male probands included in this study were diagnosed as MPS Ⅰ patients in Peking Union Medical College Hospital,case 1 was 2 years old and case 2 was 5 years old.Genomic DNA was extracted from leucocytes in the 2 patients and 2 mothers' cultured amniocytes.IDUA gene DNA sequence was amplified by polymerase chain reaction(PCR)and the PCR products were sequenced directly.Novel mutations were analyzed in 100 normal chromosomes.Result The genotype of case 1 was p.L238R/c.883InsC,while of case 2 was c.531InsT/p.L346R.The fetal case 1 did not inherit the same pathogenic inherited the same pathogenic mutations with the proband,the genotype of fetal 2 was c.531InsT/p.L346R,in 2 MPS Ⅰ patients,p.L238R,c.883InsC,c.531InsT were novel.The fetal case 1 was diagnosed as normal fetus while the fetus 2 was diagnosed as affected.The results of the two kinds of prenatal diagnostic methods were correspondent with each other.     

Impact of Enzyme Replacement Therapy on Linear Growth in Korean Patients with Mucopolysaccharidosis Type II (Hunter Syndrome)

Hunter syndrome (or mucopolysaccharidosis type II [MPS II]) arises because of a deficiency in the lysosomal enzyme iduronate-2-sulfatase. Short stature is a prominent and consistent feature in MPS II. Enzyme replacement therapy (ERT) with idursulfase (Elaprase®) or idursulfase beta (Hunterase®) have been developed for these patients. The effect of ERT on the growth of Korean patients with Hunter syndrome was evaluated at a single center. This study comprised 32 patients, who had received ERT for at least 2 yr; they were divided into three groups according to their ages at the start of ERT: group 1 (<6 yr, n=14), group 2 (6-10 yr, n=11), and group 3 (10-20 yr, n=7). The patients showed marked growth retardation as they got older. ERT may have less effect on the growth of patients with the severe form of Hunter syndrome. The height z-scores in groups 2 and 3 revealed a significant change (the estimated slopes before and after the treatment were -0.047 and -0.007, respectively: difference in the slope, 0.04; P<0.001). Growth in response to ERT could be an important treatment outcome or an endpoint for future studies.

Graphical Abstract

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Disruption of enamel crystal formation quantified by synchrotron microdiffraction

Objectives

To understand the pathology of the ultrastructure of enamel affected by systemic disorders which disrupt enamel tissue formation in order to give insight into the precise mechanisms of matrix-mediated biomineralization in dental enamel in health and disease.

Methods

Two-dimensional synchrotron X-ray diffraction has been utilized as a sophisticated and useful technique to spatially quantify preferred orientation in mineralized healthy deciduous dental enamel, and the disrupted crystallite organization in enamel affected by a systemic disease affecting bone and dental mineralization (mucopolysaccharidosis Type IVA and Type II are used as examples). The lattice spacing of the hydroxyapatite phase, the crystallite size and aspect ratio, and the quantified preferred orientation of crystallites across whole intact tooth sections, have been determined using synchrotron microdiffraction.

Results

Significant differences in mineral crystallite orientation distribution of affected enamel have been observed compared to healthy mineralized tissue. The gradation of enamel crystal orientation seen in healthy tissue is absent in the affected enamel, indicating a continual disruption in the crystallite alignment during mineral formation.

Conclusions

This state of the art technique has the potential to provide a unique insight into the mechanisms leading to deranged enamel formation in a wide range of disease states.

Clinical relevance

Characterising crystal orientation patterns and geometry in health and following disruption can be a powerful tool in advancing our overall understanding of mechanisms leading to the tissue phenotypes seen clinically. Findings can be used to inform the appropriate dental management of these tissues and/or to investigate the influence of therapeutic interventions or external stressors which may impact on amelogenesis.     

Combined aortic and mitral valve replacement in an adult with mucopolysaccharidosis (Maroteaux-Lamy syndrome)

Summary A 41-year-old man with aortic stenosis, mitral stenosis, and tricuspid regurgitation due to Maroteaux-Lamy syndrome underwent aortic and mitral valve replacement with tricuspid annuloplasty. The annular diameter of the aortic and mitral valves was extremely small. The valve prostheses were 19 mm in diameter in the aortic position and 25 mm in the mitral position. Histologically, the valves showed thickening and hyalinization of the collagen fibers, and the presence of foamy cells that contained a large quantity of pure acid mucopolysaccharide. On an echocardiographic examination performed 2 years after the surgery, the peak systolic gradient of the trans-aortic valve was 18 mmHg at rest, and 26 mmHg during exercise. Careful observation of the residual pressure gradient will be needed. The patient's present New York Heart Association (NYHA) status is grade I and he has returned to work.