Mucopolysaccharidosis type I: identification of alpha-L-iduronidase mutations in Tunisian families]

Mucopolysaccharidosis type I (MPS I) is a lysosomal disease due to mutations in the gene encoding alpha-l-iduronidase (IDUA) leading to variable clinical phenotypes with progressive severe organomegaly, bone and neurological involvement in the most severe forms. The aim of our study was to propose in Tunisia a strategy of molecular and prenatal diagnosis of the MPS I. POPULATION AND METHODS: Our study was carried out on 8 MPS I patients recruited from different Tunisian regions and issued from 5 unrelated families. All the patients were offspring of consanguineous marriages. RESULTS: The clinical and biological study led to diagnose 5 Hurler patients and 3 Hurler-Scheie patients. Three IDUA mutations were identified by molecular analysis within 6 different families: a novel mutation p.F602X and 2 already described mutations p.P533R and p.R628X. DISCUSSION: MPS I is a heterogeneous disease characterized by variability of the phenotypes. The missense mutation p.P533R associated with the intermediate phenotype was the most frequent in the Tunisian but also in the Moroccan population. In Tunisia, the incidence of p.P533R mutation seems to be associated with the high frequency of consanguineous marriages. CONCLUSION: The identification of known MPS I mutations (p.P533R and p.R628X) and of the novel mutation p.F602X permits reliable genetic counselling of at-risk relatives and molecular prenatal diagnosis.     

Biochemical and molecular analysis of mucopolysaccharidoses in Turkey

The mucopolysaccharidoses (MPSs) are a family of heritable disorders caused by deficiency of lysosomal enzymes needed to degrade glycosaminoglycans (GAGs). The undegraded or partially degraded GAGs are stored in lysosomes and/or excreted in urine. In our study, 118 patients seen over the past 20 years and suspected to have lysosomal storage disorders (LSDs) were subjected to clinical and biochemical analysis at Hacettepe University Children's Hospital. We analyzed urine and blood samples from 42 patients given a clinical MPS diagnosis. Using urine screening technique, we were able to show that 34 of the 42 patients had MPS condition. Further analysis of eight patients with normal urine MPS patterns revealed four patients as likely to have alpha-mannosidosis, fucosidosis, sialidosis, and aspartylglucosaminuria (one each). Four patients had normal oligosaccharide patterns. We were able to clearly identify 4 MPS I, 2 MPS II, 5 MPS IIIA, 8 MPS IIIB, 11 MPS IVA, 3 MPS VI, and 1 MPS IIIC patients. These results provided biochemical diagnosis for these 34 patients, and clearly show that Turkey has a higher incidence of MPS IVA, IIIB, and IIIA than of previously suspected MPS types. Molecular analysis of four MPS I patients revealed three polymorphisms which have been previously reported (A314, T388, and A461T). In MPS II patients, mutation analysis identified one previously detected (R172X) and one novel mutation (W109C).     

粘多糖贮积症Ⅱ型IDS基因的1343-TT新突变

目的研究中国粘多糖贮积症Ⅱ型（MPSⅡ）艾杜糖-2-硫酸酯酶（IDS）的基因突变,为产前基因诊断打下基础。方法应用尿粘多糖含量检测、聚合酶链反应．变性高效液相色谱（PCR-DHPLC）对1例MPSⅡ患儿及其父母的IDS基因的突变热点exons9,3,8,进行突变检测,并对PCR-DHPLC检出的突变样品进行直接测序。结果经PCR-DHPLC分析,发现患儿的IDS基因exon9有明显异常峰形;DNA序列分析进一步发现,患儿IDS基因的exon9发生1343-TT新移码突变,突变部位在第407位密码子（TTT）内,即IDS基因cDNA第1343bp的T后缺失了2个T,并在第429位提前遇上终止密码TGA,导致肽链从550个氨基酸缩短至428个。患儿为这一突变的半合子,而其母为这一突变的杂合子。结论新发现的移码突变（1343-TT）导致肽链比正常的少了122个氨基酸,极可能引起酶活性大大降低,因此可能是该MPSⅡ患儿发病的真正原因。     

Hurler syndrome. Early diagnosis and successful enzyme replacement therapy: a new therapeutic approach. Case report]

Mucopolysaccharidosis type I (MPS I) is a lysosomal storage disorder due to alpha-L-iduronidase deficiency. Its severe prognosis has been significantly improved by enzyme replacement therapy using recombinant human alpha-L-iduronidase (laronidase). We report the case of a boy who was diagnosed at 19 months of age with Hurler's disease, the most severe form of MPS I, and received thereafter a treatment by laronidase, resulting in clinical and biological improvement. The aim of this case report is to draw physicians' attention on the presenting signs of Hurler's disease, in order to enable an earlier diagnosis, increasing the treatment's benefits.     

Cardiac functional and histopathologic findings in humans and mice with mucopolysaccharidosis type I: implications for assessment of therapeutic interventions in hurler syndrome

Hurler syndrome (mucopolysaccharidosis type I [MPS I]) is a uniformly lethal autosomal recessive storage disease caused by absence of the enzyme alpha-l-iduronidase (IDUA), which is involved in lysosomal degradation of sulfated glycosaminoglycans (GAGs). Cardiomyopathy and valvar insufficiency occur as GAGs accumulate in the myocardium, spongiosa of cardiac valves, and myointima of coronary arteries. Here we report the functional, biochemical, and morphologic cardiac findings in the MPS I mouse. We compare the cardiac functional and histopathological findings in the mouse to human MPS I. In MPS I mice, we have noted aortic insufficiency, increased left ventricular size, and decreased ventricular function. Aortic and mitral valves are thickened and the aortic root is dilated. However, murine MPS I is not identical to human MPS I. Myointimal proliferation of epicardial coronary arteries is unique to human MPS I, whereas dilation of aortic root appears unique to murine MPS I. Despite the differences between murine and human MPS I, the murine model provides reliable in vivo outcome parameters, such as thickened and insufficient aortic valves and depressed cardiac function that can be followed to assess the impact of therapeutic interventions in preclinical studies in Hurler syndrome.     

52例黏多糖病酶学分型及临床特点分析

目的：探讨黏多糖病（MPS）疾病谱及其临床特点。方法：对2009年1月至2011年12月75例高度疑似MPS患儿同时进行尿黏多糖（GAG）定量和电泳分析以及7种MPS酶学分析。采用荧光分析法分别检测白细胞α-L-艾杜糖酶、艾杜糖-2-硫酸酯酶、α-N-乙酰氨基葡糖苷酶、半乳糖胺-6-硫酸酯酶、β-半乳糖苷酶、芳基硫酸酯酶B及β-葡萄糖醛酸酶活性。结果：根据临床、放射学及酶学检查确诊MPS 52例,年龄4.0±2.2岁,其中I型5例（10%）,Ⅱ型20例（38%）,ⅣA型20例（38%）,Ⅵ型6例（12%）,Ⅶ型1例（2%）,未发现ⅢB、ⅣB型患儿。除2例ⅣA型患儿外,其余50例MPS 患儿尿GAG/Gr比值均较同龄儿增高。尿GAG定量增高者均确诊为MPS。绝大多数患儿于生后1~2岁起病,常伴有疝、心脏瓣膜病。Ⅰ、Ⅱ、Ⅵ 型患儿表现面容丑陋、皮肤粗糙、矮小、关节僵硬及活动受限,ⅣA型主要表现为矮小、骨骼畸形及关节松弛。结论：MPS Ⅱ型和ⅣA型是MPS最常见类型,其次是Ⅵ型及Ⅰ型。MPS患儿以特殊外貌为临床特点,包括面容丑陋、皮肤粗糙、矮小、骨骼畸形等。尿GAG定量测定可作为一种简便、快速、可靠的MPS筛查方法在临床上推广应用。     

Abnormalities in the hair morphology of patients with some but not all types of mucopolysaccharidoses

Mucopolysaccharidoses (MPS) are a group of inherited, progressive, metabolic diseases, caused by the deficiency of one of the enzymes involved in the degradation of glycosaminoglycans (GAGs). The disease is usually fatal, with the life span of most untreated MPS patients being between one and two decades. In this report, on the basis of scanning electron microscopy (SEM) studies, we demonstrate that, besides the many other symptoms of MPS, there are characteristic abnormalities in the hair morphology of patients suffering from some types of this disease (MPS I, MPS II, MPS IIIA, MPS IIIB), but not from other types (MPS IVA, MPS IVB, MPS VI), where the changes are minor, if any. Different GAGs accumulate in the tissues of patients suffering from the various MPS types, and analysis of the disease types in which severe hair abnormalities occur or not could suggest that the accumulation of heparan sulfate, rather than dermatan sulfate or keratan sufate, may be responsible for the major changes in hair morphology. Considerable abnormalities in hair morphology occur in patients suffering from MPS I, MPS II, MPS IIIA, and MPS IIIB, but not in patients suffering from MPS IVA, MPS IVB, and MPS VI; this feature might potentially be used as an additional test for the assessment of the efficacy of treatments for MPS patients (types I, II, IIIA, and IIIB).     

35例黏多糖贮积症Ⅳ型患儿临床特点及酶学诊断

目的总结中国人黏多糖贮积症(MPS)Ⅳ型的临床特点及酶学诊断,提供MPS鉴别诊断要点。方法对2006年6月至2011年11月因矮小伴有多发骨骼畸形就诊并诊断为MPSⅣ型患儿的临床特点、骨骼影像学、尿黏多糖定性电泳及酶活性检测结果进行回顾分析。结果 35例患儿诊断为MPSⅣ型(ⅣA型34例,ⅣB型1例),所有患儿具有不同程度的MPSⅣ型临床特点,包括矮小、脊柱发育不良、关节畸形,但智能发育正常;脊柱X线显示,胸腰椎椎体前缘鸟嘴样改变及肋骨飘带状等;80%患儿的尿液黏多糖定性阳性,尿液黏多糖电泳显示CS区带;34例MPSⅣA型患儿白细胞半乳糖胺-6-硫酸盐硫酸酯酶(GALNS)活性极低[(0.85±1.33)nmol/(17 h.mg)],1例MPSⅣB型患儿β-半乳糖苷酶(GLB1)酶活性极低[5.03 nmol/(mg.h)]。结论对临床高度怀疑MPS的患儿,可检测尿液黏多糖进行初步筛查,再以酶活性分析来确诊。     

Update of the spectrum of mucopolysaccharidoses type III in Tunisia: identification of three novel mutations and <Emphasis Type="Italic">in silico</Emphasis> structural analysis of the missense mutations

Background:Mucopolysaccharidoses type Ⅲ (MPS Ⅲ) are a group of autosomai recessive lysosomal storage diseases,caused by mutations in genes that code for enzymes involved in the lysosomal degradation of heparan sulphate:heparan sulfate sulfamidase (SGSH),a-N-acetylglucosaminidase (NAGLU),heparan sulfate acetyl-CoA:a-glucosaminide N-acetyltransferase (HGSNAT),and N-acetylglucosamine-6-sulfatase (GNS).Methods:In this study,we have performed the molecular analysis of the SGSH,NAGLU and HGSNAT genes in 10 patients from 6 different MPS Ⅲ Tunisian families.Results:In the SGSH gene,two mutations were identified:one novel (p.D477N) and one already described (p.Q365X).In the NAGLU gene,two novel mutations were discovered (p.L550P and p.E153X).For the novel missense mutations found in these two genes we performed an in silico structural analysis and the results were consistent with the clinical course of the patients harboring those mutations.Finally,in HGSNAT gene,we found the splicesite mutation c.234+1G＞A that had already been reported as relatively frequent in MPS ⅢC patients from countries surrounding the basin of the Mediterranean sea.Its presence in two Tunisian MPS ⅢC families points to the hypothesis of its peri Mediterranean origin.With the exception of the c.234+1G＞A mutation,that was identified in two unrelated MPS ⅢC families,the other identified mutations were family-specific and were always found in homozygosity in the patients studied,thus reflecting the existence of consanguinity in MPS Ⅲ Tunisian families.Conclusions:Three novel mutations are reported here,further contributing to the knowledge of the molecular basis of these diseases.The results of this study will allow carrier detection in affected families and prenatal molecular diagnosis,leading to an improvement in genetic counseling.     

Psychotic symptoms during the evolution of dementia in muco- polysaccharidosis of Hurler-Scheie phenotype

The case reported concerns a 17 1/2 year-old adolescent presenting with complete alpha-L-iduronidase deficiency. Its phenotype intermediate between Hurler's and Scheie's syndromes and the occurrence of a delirious and hallucinatory condition evolving with acute exacerbations on a constant subdelirious and excited state made this case particular. This case report is compared to the 30 in the Anglo-Saxon literature which shows, in addition to the rarity of psychiatric symptoms (one single case), the multiplicity of the possible phenotypes, reinforcing the hypothesis of a polyallelic or even non allelic mutation.     

黏多糖贮积症47例的常见酶学分型

目的 对临床疑似黏多糖贮积症患儿进行常见酶学分型.方法 收集70例临床疑似黏多糖贮积症的患儿,临床疑似黏多糖贮积症的指征包括:生长落后,丑陋面容,骨骼畸形,肝脾增大,智力落后,关节僵硬/松弛等.收集疑似黏多糖贮积症患儿外周血,分离白细胞后,用人工荧光底物法和生物化学方法,分别检测导致Ⅰ,Ⅱ,ⅣA,ⅣB,Ⅵ及Ⅶ缺陷的酶,α-L-艾杜糖酶,艾杜糖醛酸硫酸酯酶,半乳糖胺-6-硫酸硫酸酯酶,β-半乳糖苷酶,芳基硫酸酶酶B及β葡萄糖醛酸酶的活性.结果 在70例可疑患儿中,共确诊黏多糖贮积症47例,其中Ⅰ型7例(占确诊黏多糖贮积症例数的15%),Ⅱ型28例(59%),ⅣA型12例(26%),未发现ⅣB,Ⅵ及Ⅶ型的患儿.黏多糖贮积症Ⅱ型患儿临床表型多样,ⅣA型患儿中67%有典型的关节松弛表现.结论 Ⅱ型可能是中国人黏多糖贮积症中最主要的一型,其他较常见的是ⅣA型和Ⅰ型.     

Enzyme replacement therapy: efficacy and limitations

Enzyme replacement therapy (ERT) is available for mucopolysaccharidosis (MPS) I, MPS II, MPS VI, and MPS IVA. The efficacy of ERT has been evaluated in clinical trials and in many post-marketing studies with a long-term follow-up for MPS I, MPS II, and MPS VI. While ERT is effective in reducing urinary glycosaminoglycans (GAGs) and liver and spleen volume, cartilaginous organs such as the trachea and bronchi, bones and eyes are poorly impacted by ERT probably due to limited penetration in the specific tissue. ERT in the present formulations also does not cross the blood–brain barrier, with the consequence that the central nervous system is not cured by ERT. This is particularly important for severe forms of MPS I and MPS II characterized by cognitive decline. For severe MPS I patients (Hurler), early haematopoietic stem cell transplantation is the gold standard, while still controversial is the role of stem cell transplantation in MPS II. The use of ERT in patients with severe cognitive decline is the subject of debate; the current position of the scientific community is that ERT must be started in all patients who do not have a more effective treatment. Neonatal screening is widely suggested for treatable MPS, and many pilot studies are ongoing. The rationale is that early, possibly pre-symptomatic treatment can improve prognosis. All patients develop anti-ERT antibodies but only a few have drug-related adverse reactions. It has not yet been definitely clarified if high-titre antibodies may, at least in some cases, reduce the efficacy of ERT.     

Early diagnosis and management of cardiac manifestations in mucopolysaccharidoses: a practical guide for paediatric and adult cardiologists

Mucopolysaccharidoses (MPS) are a group of hereditary disorders caused by lysosomal storage of glycosaminoglycans (GAGs) and characterized by a wide variability of phenotypes from severe fetal-neonatal forms to attenuated diseases diagnosed in adult individuals. The clinical picture generally worsens with age due to progressive storage involving mucosal tissue, upper airways and lungs, bones and joints, central and peripheral nervous system, heart, liver, eye, and ear. Cardiac storage of GAGs involves valves, heart muscle, and vessels (particularly the coronary arteries), and can be specific in relation to different MPS types and enzyme defects. MPS I, II, and VI are those with the most severe cardiac involvement. The cardiologist is a key figure in MPS, and their role is expanding from cardiac-specific management to early diagnosis when the mild disease phenotypes have not yet been recognized by other specialists. Familial and personal history, electrocardiography, imaging, and laboratory findings represent important steps in the clinical investigation of these patients. New treatments have led to an increased need for cardiologists to be on the lookout for MPS patients since they can significantly improve the lives of people with MPS if they suspect the diagnosis and refer them for enzyme replacement therapy or bone marrow transplantation.     

Enzyme replacement therapy in mucopolysaccharidosis type II (Hunter syndrome): a preliminary report

Mucopolysaccharidosis type II (MPS II; Hunter syndrome) is an X-linked disease caused by a deficiency of the enzyme iduronate-2-sulphatase (IDS), which results in the lysosomal accumulation of glycosaminoglycans (GAG). This paper describes a knockout mouse model of MPS II which has been used to assess the effect of enzyme replacement therapy. Therapy with IDS results in a marked decrease in urinary GAGs, as well as reduced GAG accumulation in several tissues. These studies have been used to support the first clinical trial of recombinant IDS in patients with Hunter syndrome.     

Enzyme replacement therapy in mucopolysaccharidosis type II (Hunter syndrome): a preliminary report

Mucopolysaccharidosis type II (MPS II; Hunter syndrome) is an X-linked disease caused by a deficiency of the enzyme iduronate-2-sulphatase (IDS), which results in the lysosomal accumulation of glycosaminoglycans (GAG). This paper describes a knockout mouse model of MPS II which has been used to assess the effect of enzyme replacement therapy. Therapy with IDS results in a marked decrease in urinary GAGs, as well as reduced GAG accumulation in several tissues. These studies have been used to support the first clinical trial of recombinant IDS in patients with Hunter syndrome.     

Neurobehavioral phenotypes of neuronopathic mucopolysaccharidoses

Mucopolysaccharidoses (MPS) are a group of lysosomal multisystemic, chronic, and progressive diseases characterized by the storage of glycosaminoglycans (GAGs) that may affect the central nervous system. Neuronopathic MPS such as MPS IH, MPS II, MPS IIIA–D, and MPS VII are characterized by neurocognitive regression. In severe MPS I (MPS IH, or Hurler syndrome) initial developmental trajectory is usually unremarkable but cognitive development shows a plateau by 2 to 4 years of age and then progressively regresses with aging. Patients with neuronopathic MPS II have a plateau of cognitive and adaptive development on average by 4 to 4.5 years of age, although there is significant variability, followed by progressive neurocognitive decline. In patients with classic MPS III, developmental trajectory reaches a plateau around 3 years of age, followed by regression. Sleep disturbances and behavioral problems occur early in MPS II and III with features of externalizing disorders. Acquired autism-like behavior is often observed in children with MPS III after 4–6 years of age. Impaired social and communication abilities do occur, but MPS III children do not have restricted and repetitive interests such as in autism spectrum disorder. MPS type VII is an ultra-rare neuronopathic MPS with a wide clinical spectrum from very severe with early mortality to milder phenotypes with longer survival into adolescence and adulthood. Most patients with MPS VII have intellectual disability and severely delayed speech development, usually associated with hearing impairment. Cognitive regression in neuronopathic MPS runs parallel to a significant decrease in brain tissue volume. Assessment of the developmental profile is challenging because of low cognitive abilities, physical impairment, and behavioral disturbances. Early diagnosis is crucial as different promising treatment approaches have been extensively studied in animal MPS models and are currently being applied in clinical trials.     

Enzyme replacement therapy for mucopolysaccharidosis I: a randomized, double-blinded, placebo-controlled, multinational study of recombinant human alpha-L-iduronidase (laronidase)

OBJECTIVE: To confirm the efficacy and safety of recombinant human alpha-L-iduronidase (laronidase) in patients with mucopolysaccharidosis I (MPS I). STUDY DESIGN: This was a randomized, double-blinded, multinational study of 45 patients with MPS I administered 100 U/kg (0.58 mg/kg) laronidase, or placebo intravenously weekly for 26 weeks. The coprimary efficacy end points compared the median change from baseline to week 26 between groups in percentage of predicted normal forced vital capacity (FVC) and in 6-minute walk test (6MWT) distance through the use of the Wilcoxon rank sum test. RESULTS: The laronidase (n=22) and placebo (n=23) groups had similar baseline characteristics. After 26 weeks, patients receiving laronidase compared with placebo showed mean improvements of 5.6 percentage points in percent of predicted normal FVC (median, 3.0; P=.009) and 38.1 meters in 6MWT distance (median, 38.5; P=.066; P=.039, analysis of covariance). Laronidase also significantly reduced hepatomegaly and urinary glycosaminoglycans, and, in more severely affected patients, improved sleep apnea/hypopnea and shoulder flexion. Laronidase was well-tolerated. Nearly all patients receiving enzyme had development of IgG antibodies, without apparent clinical effects. CONCLUSIONS: In patients with MPS I, laronidase significantly improves respiratory function and physical capacity, reduces glycosaminoglycan storage, and has a favorable safety profile.     

Diagnosis of mucopolysaccharidoses: How to avoid false positives and false negatives

Objective : This paper advocates a complete procedure, which includes both quantitative and qualilative analysis of urinary GAGs in the diagnosis of MPS in a clinically suspected population.Methods : Urine samples from 219 clinically suspected mucopolysaccharidoses (MPS) patients and 91 controls were analysed using a combination of methods. Quantitation of isolated urinary glycosaminoglycans (GAGs) were carried out using acid alcian blue complex formation method and qualitative urinary GAG analysis by multisolvent sequential thin layer chromatographyResults : Of the 219 patients analysed, 131 were confirmed to be suffering from MPS. Quantitation of urinary GAGs alone would have missed 60 low GAG excreting MPS patients and misdiagnosed 26 high GAG excreting nonMPS as MPS patients. Further qualitative analysis and enzyme estimation were needed to identify these 60 low GAG excreting MPS patients and 26 high GAG excreting non MPS patients.Conclusion : These results emphasize that quantitation of urinary GAGs alone cannot diagnose MPS patients, it should be coupled with qualitative analysis and enzyme estimations for differential/definitive diagnosis.     

Pre-stem cell transplantation enzyme replacement therapy in Hurler syndrome does not lead to significant antibody formation or delayed recovery of the endogenous enzyme post-transplant: a case report

Combined enzyme replacement therapy (ERT) and stem cell transplant (SCT) were done for a two year old boy with severe Hurler syndrome(HS) with the aim to decrease transplant related complications. He tolerated both the procedures well without any major complications. Urine glycosaminoglycans (GAGs) decreased post-transplant and child has improved clinically and neurologically. Insignificant titers of the anti-iduronidase antibodies which developed post-transplant did not affect the transplant outcome or the endogenous recovery of the alpha-L-iduronidase enzyme.     

Mucopolysaccharidosis I presenting with endocardial fibroelastosis of infancy

We describe two female infants with Hurler syndrome (mucopolysaccharidosis I) whose deaths are attributed to cardiac failure with associated, autopsy-confirmed endocardial fibroelastosis. One infant had confirmed alpha-L-iduronidase deficiency in cultured dermal fibroblasts, and the other infant had histologic evidence of tissue mucopolysaccharide accumulation at autopsy and a sibling with confirmed alpha-L-iduronidase deficiency and the Hurler syndrome phenotype. Clear cells ("Hurler" cells) were identified within the myocardium and endocardium of both infants. We propose that the ventricular mural accumulation of mucopolysaccharides induced extensive proliferation of elastic or collagen fibers within the endocardium. Cardiac failure may precede recognition of clinical and roentgenographic features of Hurler syndrome. Our findings and a literature review suggest that certain heritable storage disorders, including mucopolysaccharidosis I, should be considered when infants have clinical electrocardiographic and echocardiographic findings consistent with endocardial fibroelastosis or have autopsy-documented endocardial fibroelastosis.