Causes of death and clinical characteristics of 34 patients with Mucopolysaccharidosis II in Taiwan from 1995-2012

Long-term cardiovascular outcomes and mortality with enzyme replacement therapy in patients with mucopolysaccharidosis type II

Mucopolysaccharidosis type II (MPS II) is a rare multisystemic lysosomal disorder in which cardiac issues can lead to serious dysfunction and an increased risk of fatal cardiac failure. However, studies on major adverse cardiac event (MACE) outcomes in MPS II are lacking. This study evaluated the cardiovascular outcomes and impact of enzyme replacement therapy (ERT) in patients with MPS II in South Korea. In this national cohort study, utilizing data from the National Health Insurance Database, we evaluated 127 patients with MPS II over a 14-year period to investigate the effects of ERT on MACE and all-cause mortality. We tracked MACE incidence, defined by hospitalizations for cardiovascular events, from diagnosis and adjusted the hazard ratios for MACE using Cox modeling. Over an average follow-up period of 7.3 years, we identified 16 cases of MACE among patients (17.35 per 1000 person-years; 95% confidence interval, 10.74-26.83). Patients receiving ERT exhibited a significantly lower incidence of MACE than untreated patients, with cumulative incidences showing a marked difference of 8.3 years. Notably, initiating ERT at earlier stages post-diagnosis was associated with improved outcomes, underscoring the importance of timely treatment. The key risk factors for MACE included specific arrhythmias, a history of invasive procedures, and depression. Early ERT significantly reduced MACE risk and increased survival in patients with MPS II. This underscores the importance of prompt treatment initiation and comprehensive care to address key risk factors and advocates for an expanded therapeutic strategy to enhance MPS II outcomes.

Causes of death in mucopolysaccharidoses

Mucopolysaccharidoses are inherited metabolic diseases caused by mutations in genes encoding enzymes required for degradation of glycosaminoglycans. A lack or severe impairment of activity of these enzymes cause accumulation of GAGs which is the primary biochemical defect. Depending on the kind of the deficient enzyme, there are 12 types and subtypes of MPS distinguished. Despite the common primary metabolic deficit (inefficient GAG degradation), the course and symptoms of various MPS types can be different, though majority of the diseases from the group are characterized by severe symptoms and significantly shortened live span. Here, we analysed the frequency of specific, direct causes of death of patients with different MPS types, the subject which was not investigated comprehensively to date. We examined a total of 1317 cases of death among MPS patients, including 393 cases of MPS I, 418 cases of MPS II, 232 cases of MPS III, 45 cases of MPS IV, 208 cases of MPS VI, and 22 cases of MPS VII. Our analyses indicated that the most frequent causes of death differ significantly between MPS types, with cardiovascular and respiratory failures being predominant in MPS I, MPS II, and MPS VI, neurological deficits in MPS III, respiratory issues in MPS IV, and hydrops fetalis in MPS VII. Results of such studies suggest what specific clinical problems should be considered with the highest priority in specific MPS types, apart from attempts to correct the primary causes of the diseases, to improve the quality of life of patients and to prolong their lives.

Biomarkers of Glycosaminoglycans (GAG) accumulation in patients with mucopolysaccharidosis type VI-LeukoGAG, Corneal Opacification (COM) and Carotid Intima Media Thickening (CIMT)

Mucopolysaccharidosis type VI (MPS VI) is an autosomal recessive lysosomal storage disorder characterized by deficient activity of arylsulfatase B enzyme (ASB) resulting in cellular accumulation of dermatan sulfate (DS) and chondroitin sulfate (CS) that leads to cell injury. Urinary glycosaminoglycans (GAG) are often used as a biomarker in MPS diseases for diagnosis and to monitor treatment efficacy. This study evaluated leukocyte GAGs (leukoGAG) and skin GAGs as alternate biomarkers representing intracellular GAG changes in patients with MPS VI and treated with enzyme replacement therapy (ERT). In addition, we evaluated corneal opacification measurements (COM) and carotid intima media thickness (CIMT) as indicators of GAG accumulation and tissue injury. The study was performed in a serial two-step design in a single center. A quantitative method to measure leukoGAG levels in leukocytes was developed in Study 1 to compare the GAG levels between MPS VI patients and a control group and to assess correlations between leukoGAG and urineGAG. Study 2 validated the leukoGAG measurement, assessed the effect of ERT infusion on leukoGAG and ASB activity in leukocytes, identified correlations between leukoGAG and other biomarkers, and assessed differences in GAG accumulation between MPS VI patients and control subjects. In Study 1, leukoCS and leukoDS levels were significantly higher in the MPS VI group than the control group (leukoCS: 37.9 ± 10.2 and 2.9 ± 1.5 μg/μg protein, respectively, p = 0.005; leukoDS: 0.26 ± 0.2 and 0.0 ± 0.0 μg/μg protein, respectively, p = 0.028) with positive correlations between leukoCS and urine CS and leukoDS and urineDS. In Study 2, leukoCS (32.0 ± 11.8 vs 6.9 ± 3.1 μg/mg protein, p = 0.005) and leukoDS (0.4 ± 0.1 and 0.2 ± 0.1 μg/mg protein, p = 0.020) were significantly higher compared with control subjects. Thus, these results highlight the potential of leukoGAG as a new biomarker representing intracellular GAG accumulation in MPS VI patients and may be valuable for patient management.

Evaluation of cardiac findings in mucopolysaccharidosis

PURPOSE

Mucopolysaccharidoses (MPS) are a group of rare genetic diseases and heart involvement is one of the important conflicts in most types, which may cause serious complications. We used M-Mode and two-dimensional speckle tracking echocardiography (2D-STE) to explore cardiovascular involvements in MPS patients.

METHOD

The present cross-sectional study investigated the frequency of cardiac involvements in MPS patients. Included participants were MPS types I, II, III, IV, and VI who underwent specialized echocardiography exams to assess valvular function, systolic and diastolic function, left ventricular ejection fraction (LVEF), and global longitudinal strain (GLS).

RESULTS

35 patients were enrolled in this study. The total mean age of patients was 9.58 ± 5.11 years and 71.4% were male. Type IV (40%) and type III (31.4%) were the most frequent MPS. Although LVEF did not differ notably among MPS types, GLS was significantly different (p = 0.029). Mitral regurgitation was observed remarkably more in MPS type III (p = 0.001) while mitral stenosis was more common in type III (p = 0.007). There was a significant association between LVEF and GLS (β= -0.662; p = 0.025) and between LVEF and MPS type (β = 1.82; p = 0.025) when adjusted for GLS.

CONCLUSION

Cardiac complications are very common and are one of the most important causes of death in MPS patients. 2D-STE seems to be superior to M-Mode for detection of early and subclinical cardiac dysfunction in MPS patients.

Metabolic Cardiomyopathies and Cardiac Defects in Inherited Disorders of Carbohydrate Metabolism: A Systematic Review

Heart failure (HF) is a progressive chronic disease that remains a primary cause of death worldwide, affecting over 64 million patients. HF can be caused by cardiomyopathies and congenital cardiac defects with monogenic etiology. The number of genes and monogenic disorders linked to development of cardiac defects is constantly growing and includes inherited metabolic disorders (IMDs). Several IMDs affecting various metabolic pathways have been reported presenting cardiomyopathies and cardiac defects. Considering the pivotal role of sugar metabolism in cardiac tissue, including energy production, nucleic acid synthesis and glycosylation, it is not surprising that an increasing number of IMDs linked to carbohydrate metabolism are described with cardiac manifestations. In this systematic review, we offer a comprehensive overview of IMDs linked to carbohydrate metabolism presenting that present with cardiomyopathies, arrhythmogenic disorders and/or structural cardiac defects. We identified 58 IMDs presenting with cardiac complications: 3 defects of sugar/sugar-linked transporters (GLUT3, GLUT10, THTR1); 2 disorders of the pentose phosphate pathway (G6PDH, TALDO); 9 diseases of glycogen metabolism (GAA, GBE1, GDE, GYG1, GYS1, LAMP2, RBCK1, PRKAG2, G6PT1); 29 congenital disorders of glycosylation (ALG3, ALG6, ALG9, ALG12, ATP6V1A, ATP6V1E1, B3GALTL, B3GAT3, COG1, COG7, DOLK, DPM3, FKRP, FKTN, GMPPB, MPDU1, NPL, PGM1, PIGA, PIGL, PIGN, PIGO, PIGT, PIGV, PMM2, POMT1, POMT2, SRD5A3, XYLT2); 15 carbohydrate-linked lysosomal storage diseases (CTSA, GBA1, GLA, GLB1, HEXB, IDUA, IDS, SGSH, NAGLU, HGSNAT, GNS, GALNS, ARSB, GUSB, ARSK). With this systematic review we aim to raise awareness about the cardiac presentations in carbohydrate-linked IMDs and draw attention to carbohydrate-linked pathogenic mechanisms that may underlie cardiac complications.

Phenotypic and genetic characteristics of 130 patients with mucopolysaccharidosis type II: A single-center retrospective study in China

Background: Mucopolysaccharidosis Type II (MPS II) is a rare, progressive and ultimately fatal X-linked lysosomal storage disorder caused by mutations in the iduronate-2-sulfatase (IDS) gene. This report conducted a retrospective analysis to investigate the clinical characteristics, genotypes and management strategies in a large cohort of Chinese patients with MPS II. Methods: In this study, we explored 130 Chinese patients with MPS II between September 2008 and April 2022. Clinical manifestations, auxiliary examination, IDS pathogenic gene variants and IDS enzyme activity, surgical history were analysed in the study. Results: A total of 130 patients were enrolled and the mean age at diagnosis was 5 years old. This study found the most common symptoms in our patients were claw-like hands, followed by coarse facial features, birthmarks (Mongolian spot), delayed development, inguinal or umbilical hernia. The most commonly cardiac manifestations were valve abnormalities, which were mitral/tricuspid valve regurgitation (71.9%) and aortic/pulmonary valve regurgitation (36.8%). We had found 43 different IDS pathogenic gene variants in 55 patients, included 16 novel variants. The variants were concentrated in exon 9 (20% = 11/55), exon 3 (20% = 11/55) and exon 8 (15% = 8/55). A total of 50 patients (38.5%) underwent surgical treatment, receiving a total of 63 surgeries. The average age of first surgery was 2.6 years, and the majority of surgery (85.7%, 54/63) was operated before 4 years old. The most common and earliest surgery was hernia repair. Three patients were died of respiratory failure. Conclusion: This study provided additional information on the clinical, cardiac ultrasound and surgical procedure in MPS II patients. Our study expanded the genotype spectrum of MPS II. Based on these data, characterization of MPS II patients group could be used to early diagnosis and treatment of the disease.

Newborn Screening Program for Mucopolysaccharidosis Type II and Long-Term Follow-Up of the Screen-Positive Subjects in Taiwan

Background: Mucopolysaccharidosis II (MPS II) is an X-linked disorder resulting from a deficiency in lysosomal enzyme iduronate-2-sulfatase (IDS), which causes the accumulation of glycosaminoglycans (GAGs) in the lysosomes of many tissues and organs, leading to progressive cellular dysfunction. An MPS II newborn screening program has been available in Taiwan since 2015. The aim of the current study was to collect and analyze the long-term follow-up data of the screen-positive subjects in this program. Methods: From August 2015 to April 2022, 548,624 newborns were screened for MPS II by dried blood spots using tandem mass spectrometry, of which 202 suspected infants were referred to our hospital for confirmation. The diagnosis of MPS II was confirmed by IDS enzyme activity assay in leukocytes, quantitative determination of urinary GAGs by mass spectrometry, and identification of the IDS gene variant. Results: Among the 202 referred infants, 10 (5%) with seven IDS gene variants were diagnosed with confirmed MPS II (Group 1), 151 (75%) with nine IDS gene variants were classified as having suspected MPS II or pseudodeficiency (Group 2), and 41 (20%) with five IDS gene variants were classified as not having MPS II (Group 3). Long-term follow-up every 6 months was arranged for the infants in Group 1 and Group 2. Intravenous enzyme replacement therapy (ERT) was started in four patients at 1, 0.5, 0.4, and 0.5 years of age, respectively. Three patients also received hematopoietic stem cell transplantation (HSCT) at 1.5, 0.9, and 0.6 years of age, respectively. After ERT and/or HSCT, IDS enzyme activity and the quantity of urinary GAGs significantly improved in all of these patients compared with the baseline data. Conclusions: Because of the progressive nature of MPS II, early diagnosis via a newborn screening program and timely initiation of ERT and/or HSCT before the occurrence of irreversible organ damage may lead to better clinical outcomes. The findings of the current study could serve as baseline data for the analysis of the long-term effects of ERT and HSCT in these patients.

Features and behavior of valvular abnormalities in adolescent and adult patients in mucopolysaccharidosis: an echocardiographic study

Mucopolysaccharidoses, a rare inherited disorder of lysosomal storage, account for less than 0.1% of all genetic diseases.  The penetrance is highly variable and clinically it varies from severe fetal-neonatal forms to attenuated diseases diagnosed in adult individuals. The majority of the patients have been reported to show cardiac abnormalities since pediatric age, however, there is a minority of patients with attenuated disease diagnosed in the adolescent and adult age. The haematopoietic stem cell transplantation and enzyme replacement therapy are the current therapies for these disorders. Thanks to these treatments, Mucopolysaccharidoses patients live longer than in the past. Even though enzyme replacement therapy has been demonstrated to reduce left ventricular mass in patients with cardiomyopathy, the efficacy on valve abnormalities has not been clearly demonstrate yet. Furthermore, thanks to the current therapy, to better understanding and to the advent on new technologies, an increasing number of adolescent and adult patients diagnosed with MPS are followed up in the adult echocardiographic laboratory. Indeed, a systematic descriptive study describing the echocardiographic features of valvular involvement and their evolution in adolescent and adult patients lacks of medical literature and this was the aim of our investigation. Our results showed that all the valves are affected, mainly the mitral valve with a higher prevalence compared to the pediatric age.  The echocardiographic features of MPS differs from other valvular disease of adolescent and adult age, and knowing them can avoid misdiagnosis. Our observations also suggest that the progression of cardiac involvement slows after the initiation of the therapy in our group of age. Further studies on larger population are required to confirm our results.

Natural progression of cardiac features and long-term effects of enzyme replacement therapy in Taiwanese patients with mucopolysaccharidosis II

Background

Cardiac abnormalities have been observed in patients with mucopolysaccharidosis type II (MPS II). The aim of this study was to investigate the cardiac features and natural progression of Taiwanese patients with MPS II, and evaluate the impact of enzyme replacement therapy (ERT) on cardiac structure and function.

Methods

The medical records and echocardiograms of 48 Taiwanese patients with MPS II (median age, 6.9 years; age range, 0.1–27.9 years) were reviewed. The relationships between age and each echocardiographic parameter were analyzed.

Results

The mean z-scores of left ventricular mass index (LVMI), interventricular septum diameter in diastole (IVSd), left ventricular posterior wall diameter in diastole (LVPWd), and aortic diameter were 1.10, 2.70, 0.95 and 1.91, respectively. Z scores > 2 were identified in 33%, 54%, 13%, and 46% for LVMI, IVSd, LVPWd, and aortic diameter, respectively. The most prevalent cardiac valve abnormality was mitral regurgitation (MR) (56%), followed by aortic regurgitation (AR) (33%). The severity of mitral stenosis (MS), MR, aortic stenosis (AS), AR, and the existence of valvular heart disease were all positively correlated with increasing age (p < 0.01). We also compared the echocardiographic parameters between two groups: (1) 12 patients who had up to 17 years of follow-up echocardiographic data without ERT, and (2) nine patients who had up to 12 years of follow-up data with ERT. The results showed that z-score changes of LVMI significantly improved in the patients who received ERT compared to those who did not receive ERT (0.05 versus 1.52, p < 0.05). However, the severity score changes of MS, MR, AS, and AR all showed gradual progression in both groups (p > 0.05).

Conclusions

High prevalence rates of valvular heart disease and cardiac hypertrophy were observed in the MPS II patients in this study. The existence and severity of cardiac hypertrophy and valvular heart disease in these patients worsened with increasing age, reinforcing the concept of the progressive nature of this disease. ERT for MPS II appeared to be effective in stabilizing or reducing the progression of cardiac hypertrophy, but it only had a limited effect on valvulopathy.

Aortic Root Dilatation in Taiwanese Patients with Mucopolysaccharidoses and the Long-Term Effects of Enzyme Replacement Therapy

Background: Cardiovascular abnormalities have been observed in patients with mucopolysaccharidosis (MPS) of any type, with the most documented abnormalities being valvular regurgitation and stenosis and cardiac hypertrophy. Only a few studies have focused on aortic root dilatation and the long-term effects of enzyme replacement therapy (ERT) in these patients. Methods: We reviewed echocardiograms of 125 Taiwanese MPS patients (age range, 0.1 to 19.1 years; 11 with MPS I, 49 with MPS II, 25 with MPS III, 29 with MPS IVA, and 11 with MPS VI). The aortic root diameter was measured at the sinus of Valsalva. Results: Aortic root dilatation (z score >2) was observed in 47% of the MPS patients, including 66% of MPS IV, 51% of MPS II, 45% of MPS VI, 28% of MPS III, and 27% of MPS I patients. The mean aortic root diameter z score was 2.14 (n = 125). The patients with MPS IV had the most severe aortic root dilatation with a mean aortic root diameter z score of 3.03, followed by MPS II (2.12), MPS VI (2.06), MPS III (1.68), and MPS I (1.03). The aortic root diameter z score was positively correlated with increasing age (n = 125, p < 0.01). For the patients with MPS II, III, and IV, aortic root diameter z score was also positively correlated with increasing age (p < 0.01). For 16 patients who had received ERT and had follow-up echocardiographic data (range 2.0–16.2 years), the mean aortic root diameter z score change was −0.46 compared to baseline (baseline 2.49 versus follow-up 2.03, p = 0.490). Conclusions: Aortic root dilatation was common in the patients with all types of MPS, with the most severe aortic root dilatation observed in those with MPS IV. The severity of aortic root dilatation worsened with increasing age, reinforcing the concept of the progressive nature of this disease. ERT for MPS appears to stabilize the progression of aortic root dilatation.

Survival and diagnostic age of 175 Taiwanese patients with mucopolysaccharidoses (1985-2019)

Background

Mucopolysaccharidoses (MPSs) are a group of inherited metabolic diseases, which are characterized by the accumulation of glycosaminoglycans, and eventually lead to the progressive damage of various tissues and organs.

Methods

An epidemiological study of MPS in Taiwan was performed using multiple sources. The survival and diagnostic age for different types of MPS between 1985 and 2019 were evaluated.

Results

Between 1985 and 2019, there were 175 patients diagnosed with MPS disorders in the Taiwanese population, with a median diagnostic age of 3.9 years. There were 21 (12%), 78 (45%), 33 (19%), 32 (18%) and 11 (6%) patients diagnosed with MPS I, II, III, IV and VI, respectively, with median diagnostic ages of 1.5, 3.8, 4.7, 4.5 and 3.7 years, respectively. Diagnosis of MPS patients was significantly earlier in recent decades (p < 0.01). Pilot newborn screening programs for MPS I, II, VI, IVA, and IIIB were progressively introduced in Taiwan from 2016, and 48% (16/33) of MPS patients diagnosed between 2016 and 2019 were diagnosed by one of these screening programs, with a median diagnostic age at 0.2 years. For patients born between 2016 and 2019, up to 94% (16/17) were diagnosed with MPS via the newborn screening programs. At the time of this study, 81 patients had passed away with a median age at death of 15.6 years. Age at diagnosis was positively correlated with life expectancy (p < 0.01). Life expectancy also significantly increased between 1985 and 2019, however this increase was gradual (p < 0.01).

Conclusions

The life expectancy of Taiwanese patients with MPS has improved in recent decades and patients are being diagnosed earlier. Because of the progressive nature of the disease, early diagnosis by newborn screening programs and timely implementation of early therapeutic interventions may lead to better clinical outcomes.

Type 1 tyrosinemia in Finland: a nationwide study

Background

Introduction of nitisinone and newborn screening (NBS) have transformed the treatment of type 1 tyrosinemia, but the effects of these changes on the long-term outcomes remain obscure. Also, the predictors for later complications, the significance of drug levels and the normalization of laboratory and imaging findings are poorly known. We investigated these issues in a nationwide study.

Results

Type 1 tyrosinemia was diagnosed in 22 children in 1978–2019 in Finland. Incidence was 1/90,102, with a significant enrichment in South Ostrobothnia (1/9990). Median age at diagnosis was 5 (range 0.5–36) months, 55% were girls and 13 had homozygotic Trp262X mutation. Four patients were detected through screening and 18 clinically, their main findings being liver failure (50% vs. 100%, respectively, p = 0.026), ascites (0% vs. 53%, p = 0.104), renal tubulopathy (0% vs. 65%, p = 0.035), rickets (25% vs. 65%, p = 0.272), growth failure (0% vs. 66%, p = 0.029), thrombocytopenia (25% vs. 88%, p = 0.028) and anaemia (0% vs. 47%, p = 0.131). One patient was treated with diet, seven with transplantation and 14 with nitisinone. Three late-diagnosed (6–33 months) nitisinone treated patients needed transplantation later. Kidney dysfunction (86% vs. 7%, p = 0.001), hypertension (57% vs. 7%, p = 0.025) and osteopenia/osteoporosis (71% vs. 14%, p = 0.017) were more frequent in transplanted than nitisinone-treated patients. Blood/serum alpha-fetoprotein decreased rapidly on nitisinone in all but one patient, who later developed intrahepatic hepatocellular carcinoma. Liver values normalized in 31 months and other laboratory values except thrombocytopenia within 18 months. Imaging findings normalized in 3–56 months excluding five patients with liver or splenic abnormalities. Low mean nitisinone concentration was associated with higher risk of severe complications (r = 0.758, p = 0.003) despite undetectable urine succinylacetone.

Conclusions

Prognosis of type 1 tyrosinemia has improved in the era of nitisinone, and NBS seems to provide further benefits. Nevertheless, the long-term risk for complications remains, particularly in the case of late diagnosis and/or insufficient nitisinone levels.

Safety and efficacy of idursulfase in the treatment of mucopolysaccharidosis II (Hunter syndrome): a post-marketing study in Japan

OBJECTIVES

Enzyme replacement therapy with idursulfase has been shown to improve somatic signs and symptoms of mucopolysaccharidosis type II (MPS II). Idursulfase is available in Japan (since 2007), based on the outcome of clinical trials conducted in the United States, but data from Japanese patients are limited.

METHODS

This was a postmarketing study of Japanese MPS II patients treated with 0.5 mg/kg intravenous idursulfase weekly, conducted over a period of 8 years after initial administration. Assessments included the safety profile, survival rate, degree of clinical improvement, change in urinary uronic acid (UA) concentration, and 6-minute walk test (6MWT).

RESULTS

The safety and efficacy analysis populations included 145 and 143 patients, respectively. The incidence of serious adverse events was 42.8% and the incidence of adverse drug reactions was 48.3%. The 7-year survival rate was 82.7%. Improvements in the clinical features of hepatosplenomegaly, skin, joint, and respiratory disorders were reported (per investigator's assessment). The mean change in urinary UA concentration was -128.39 mg/g creatinine, and that of 6MWT walking distance was +31.8 m.

CONCLUSION

Long-term idursulfase treatment was well tolerated, and effective in improving clinical features, reducing urinary UA, and slowing disease progression in Japanese MPS II patients.

Case report of endoprosthesis -Y implantation in severe respiratory failure in the MPSII patient; comparison with literature data

Background

The tracheobronchomalacia is a life-threatening complication of mucopolysaccharidosis (MPS) without known effective, optimal treatment. The severe expiratory collapse of the trachea and bronchi is one of causes of the high rate of deaths in the course of airway impairment in MPSII patients.

Case presentation

Due to the adynamic tracheobronchomalacia despite of enzymatic treatment (ERT) in our MPSII patient, a life-saving tracheal bifurcated type-Y endoprosthesis (a self-expanding, metal stent for the prosthesis of tracheal and bronchial stenosis) was implanted. In the followed months, the breathing efficiency improved, but then gradual worsening, progression of bronchi occlusion at the stent border resulted in patient’s death.

Conclusion

The Y-stent implantation appears to be a short-term, life-saving solution without satisfactory long-term effects due to the progress of peripheral bronchomalacia and increased tissue proliferation and granulation, that arises during the illness’ course.

Respiratory Dysfunction in Children and Adolescents with Mucopolysaccharidosis Types I, II, IVA, and VI

Mucopolysaccharidosis (MPS) is a rare genetic disease involving active storage of glycosaminoglycans (GAGs). Accumulation of GAGs in the connective tissues of airways leads to progressive pulmonary dysfunction. Studies conducted in Taiwan revealed mainly restrictive pulmonary dysfunction, whereas the same studies in Egypt and California revealed obstructive pulmonary dysfunction. The contradictory results and lack of studies of respiratory system in patients with MPS in Asian populations are an indication to study pulmonary impairment in patients with MPS in Kazakhstan. The prospective study of respiratory system in patients with MPS was conducted in the Scientific Centre of Paediatrics and Paediatric Surgery. Patients with MPS (n = 11) were examined for respiratory function. Different types of pulmonary dysfunction were present in MPS patients, they were mainly of a restrictive pathology. One patient with MPS II had obstructive dysfunction. Enzyme replacement therapy was provided for an average duration of four years, leading to improvements in respiratory function in two patients with total normalization in one. All observed patients had respiratory dysfunction, mainly of the restrictive type. Pulmonary impairment in patients with MPS is the main reason for death. Thus, it is necessary to follow up with pulmonary function assessments in children with MPS.

Cardiac Evaluation using Two-Dimensional Speckle-Tracking Echocardiography and Conventional Echocardiography in Taiwanese Patients with Mucopolysaccharidoses

Background: Mucopolysaccharidoses (MPSs) are a group of rare inherited metabolic disorders that can damage various organs, including the heart. Cardiac abnormalities have been observed in patients with all MPS types, with the most documented abnormalities being cardiac valvular regurgitation and stenosis, valvular thickening, and hypertrophic cardiomyopathy. Methods: Cardiac features of 53 Taiwanese patients with MPS (31 men and 22 women; age range 1.1–34.9 years; seven with MPS I, 16 with MPS II, nine with MPS III, 14 with MPS IVA, and seven with MPS VI) were evaluated using two-dimensional speckle-tracking echocardiography and conventional echocardiography. Results: The mean z scores of the global longitudinal strain (GLS), left ventricular mass index (LVMI), interventricular septum diameter in diastole (IVSd), left ventricular posterior wall diameter in diastole (LVPWd), and aortic diameter of the 53 patients with MPS were 1.71, 0.35, 1.66, 1.03, and 3.15, respectively. Furthermore, z scores >2 were identified in 45%, 13%, 40%, 13%, and 70% of the GLS, LVMI, IVSd, LVPWd, and aortic diameter, respectively. The most severe GLS was observed in those with MPS VI, followed by in those with MPS II and MPS I. The GLS z score was positively correlated with the LVMI z score (p < 0.01). Moreover, diastolic dysfunction (reversed ratio between early and late (atrial) ventricular filling velocity (E/A ratio < 1)) was identified in 12 patients (23%). Ejection and shortening fractions were abnormal in four (8%) and seven (13%) patients, respectively. Mitral regurgitation (MR) (92%) was the most common valvular heart disease, followed by aortic regurgitation (AR) (57%), mitral stenosis (MS) (21%), and aortic stenosis (AS) (15%). The z scores of the GLS and LVMI and severity scores of the MS, MR, AS, and AR were all positively correlated with increasing age (p < 0.05). Twenty patients (38%) had a left ventricular remodeling pattern. Conclusions: The most significant left ventricular myocardial deformation, hypertrophy and valvular heart disease were observed in the patients with MPS VI, II, and I, followed by those with MPS IV; in contrast, patients with MPS III had the mildest manifestations. Cardiac abnormalities in patients with MPS worsened with increasing age in accordance with the progressive nature of this disease.

Cardiac characteristics and natural progression in Taiwanese patients with mucopolysaccharidosis III

BACKGROUND

Mucopolysaccharidosis type III (MPS III), or Sanfilippo syndrome, is caused by a deficiency in one of the four enzymes involved in the lysosomal degradation of heparan sulfate. Cardiac abnormalities have been observed in patients with all types of MPS except MPS IX, however few studies have focused on cardiac alterations in patients with MPS III.

METHODS

We reviewed medical records, echocardiograms, and electrocardiograms of 26 Taiwanese patients with MPS III (five with IIIA, 20 with IIIB, and one with IIIC; 14 males and 12 females; median age, 7.4 years; age range, 1.8-26.5 years). The relationships between age and each echocardiographic parameter were analyzed.

RESULTS

Echocardiographic examinations (n = 26) revealed that 10 patients (38%) had valvular heart disease. Four (15%) and eight (31%) patients had valvular stenosis or regurgitation, respectively. The most prevalent cardiac valve abnormality was mitral regurgitation (31%), followed by aortic regurgitation (19%). However, most of the cases of valvular heart disease were mild. Three (12%), five (19%) and five (19%) patients had mitral valve prolapse, a thickened interventricular septum, and asymmetric septal hypertrophy, respectively. The severity of aortic regurgitation and the existence of valvular heart disease, aortic valve abnormalities and valvular stenosis were all positively correlated with increasing age (p < 0.05). Z scores > 2 were identified in 0, 38, 8, and 27% of left ventricular mass index, interventricular septal end-diastolic dimension, left ventricular posterior wall end-diastolic dimension, and aortic diameter, respectively. Electrocardiograms in 11 patients revealed the presence of sinus arrhythmia (n = 3), sinus bradycardia (n = 2), and sinus tachycardia (n = 1). Six patients with MPS IIIB had follow-up echocardiographic data at 1.9-18.1 years to compare with the baseline data, which showed some patients had increased thickness of the interventricular septum, as well as more patients had valvular abnormalities at follow-up.

CONCLUSIONS

Cardiac involvement in MPS III is less common and milder compared with other types of MPS. The existence of valvular heart disease, aortic valve abnormalities and valvular stenosis in the patients worsened with increasing age, reinforcing the concept of the progressive nature of this disease.

Taiwan National Newborn Screening Program by Tandem Mass Spectrometry for Mucopolysaccharidoses Types I, II, and VI

OBJECTIVE

To evaluate the initial cutoff values, rates of screen positives, and genotypes for the large-scale newborn screening program for multiple mucopolysaccharidoses (MPS) in Taiwan.

STUDY DESIGN

More than 100 000 dried blood spots were collected consecutively as part of the national Taiwan newborn screening programs. Enzyme activities were measured by tandem mass spectrometry from dried blood spot punches. Genotypes were obtained when a second newborn screening specimen again had a decreased enzyme activity. Additional clinical evaluation was then initiated based on enzyme activity and/or genotype.

RESULTS

Molecular genetic analysis for cases with low enzyme activity revealed 5 newborns with pathogenic alpha-L-iduronidase mutations, 3 newborns with pathogenic iduronate-2-sulfatase mutations, and 1 newborn was a carrier of an arylsulfatase B mutation. Several variants of unknown pathogenic significance were also identified, most likely causing pseudodeficiency.

CONCLUSIONS

The highly robust tandem mass spectrometry-based enzyme assays for MPS-I, MPS-II, and MPS-VI allow for high-throughput newborn screening for these lysosomal storage disorders. Optimized cutoff values combined with second tier testing could largely eliminate false-positive results. Accordingly, newborn screening for these lysosomal storage disorders is possible.

The relationships between urinary glycosaminoglycan levels and phenotypes of mucopolysaccharidoses

Background

The aim of this study was to use the liquid chromatography/tandem mass spectrometry (LC‐MS/MS) method to quantitate levels of three urinary glycosaminoglycans (GAGs; dermatan sulfate [DS], heparan sulfate [HS], and keratan sulfate [KS]) to help make a correct diagnosis of mucopolysaccharidosis (MPS).

Methods

We analyzed the relationships between phenotypes and levels of urinary GAGs of 79 patients with different types of MPS.

Results

The patients with mental retardation (n = 21) had significantly higher levels of HS than those without mental retardation (n = 58; 328.8 vs. 3.2 μg/ml, p < 0.001). The DS levels in the patients with hernia, hepatosplenomegaly, claw hands, coarse face, valvular heart disease, and joint stiffness were higher than those without. Twenty patients received enzyme replacement therapy (ERT) for 1–12.3 years. After ERT, the KS level decreased by 90% in the patients with MPS IVA compared to a 31% decrease in the change of dimethylmethylene blue (DMB) ratio. The DS level decreased by 79% after ERT in the patients with MPS VI compared to a 66% decrease in the change of DMB ratio.

Conclusions

The measurement of GAG fractionation biomarkers using the LC‐MS/MS method is a more sensitive and reliable tool than the DMB ratio for MPS high‐risk screening, diagnosis, subclass identification, and monitoring the efficacy of ERT.

Cardiac features and effects of enzyme replacement therapy in Taiwanese patients with Mucopolysaccharidosis IVA

BACKGROUND

Cardiac abnormalities have been observed in patients with mucopolysaccharidosis (MPS) of any type, with the most documented abnormalities being valvular heart disease and cardiac hypertrophy. However, few studies have focused on the cardiac features of MPS IVA.

METHODS

We reviewed the medical records, echocardiograms, and electrocardiograms of 32 Taiwanese patients with MPS IVA (16 males and 16 females; median age, 10.8 years; age range, 1.1 to 29.1 years) as well as the echocardiographic data of six patients who received enzyme replacement therapy (ERT) for 3-6 years.

RESULTS

Echocardiographic examinations (n = 32) revealed mean z scores of left ventricular mass index (LVMI), interventricular septum diameter in diastole (IVSd), left ventricular posterior wall diameter in diastole (LVPWd), and aortic diameter of 0.94, 2.70, 0.39, and 3.26, respectively. Z scores > 2 were identified in 25%, 50%, 29%, and 69% of the LVMI, IVSd, LVPWd, and aortic diameter values, respectively. Diastolic dysfunction [reversed ratio between early and late (atrial) ventricular filling velocity (E/A ratio < 1)] was identified in four patients (13%), however, the ejection fraction was normal (50-75%) in all of the patients. Sixteen patients (50%) had valvular heart disease and most were of mild degree. Fourteen (44%) had valvular stenosis, and 10 (31%) had regurgitation. The z scores of LVMI, IVSd, LVPWd, and aortic diameter, the severity scores of aortic stenosis and regurgitation, and the existence of a thickened interventricular septum were all positively correlated with increasing age (p < 0.05). For the 14 patients with valve thickening, the z scores of LVMI, IVSd and aortic diameter were all larger than those of the 18 patients without valve thickening (p < 0.05). For two patients who started ERT at a younger age (1.4 and 2.8 years, respectively), the z scores for LVMI, IVSd, and LVPWd all decreased after ERT.

CONCLUSIONS

A large proportion of the patients with MPS IVA had valvular heart disease and cardiac hypertrophy. Cardiac abnormalities worsened with increasing age in accordance with the progressive nature of this disease. ERT appeared to be effective in stabilizing or reducing cardiac hypertrophy, and better results may have been associated with starting ERT at a younger age.

Clinical characteristics and surgical history of Taiwanese patients with mucopolysaccharidosis type II: data from the hunter outcome survey (HOS)

BACKGROUND

Mucopolysaccharidosis type II (MPS II) is the most frequently occurring MPS in Taiwan, with an incidence of 2.05 per 100,000 live male births, but little is known about clinical characteristics and surgical history in Taiwanese patients.

METHODS

Medical history, demographics, signs and symptoms, and surgical history were analysed in all patients from Taiwanese centres in the Hunter Outcome Survey (HOS; NCT 03292887), a global, multicentre registry that collects real-world data on patients with MPS II.

RESULTS

As of January 2016, 61 male Taiwanese patients were enrolled; 49% (24/49) had received at least one infusion of idursulfase. Median (10th, 90th percentiles) ages at signs and symptom onset and at diagnosis were 2.5 (0.2, 5.5) years (n = 55) and 3.5 (1.2, 11.9) years (n = 56), respectively. Hernia, facial features consistent with MPS II and claw hands were the earliest presenting signs and symptoms (median ages of 3.2 [0.4, 12.0] years, 4.3 [1.1, 12.0] years and 4.7 [2.5, 12.2] years [n = 45, 53 and 50], respectively). More than 75% of patients had undergone a surgical procedure, most commonly hernia repair (57% of patients). Median age at first surgery for hernia repair was 4.2 (0.5, 9.8) years (n = 35). Almost one-third (31.1%) of patients had at least one surgical procedure before diagnosis, and of the 20 procedures before diagnosis, 16 were hernia repair.

CONCLUSIONS

This information from patients in HOS highlights the importance of both medical and surgical history in diagnosing MPS II in Taiwanese patients.

Case report of treatment experience with idursulfase beta (Hunterase) in an adolescent patient with MPS II

Mucopolysaccharidosis (MPS) II or Hunter syndrome is a chronic, progressive, multi-systemic illness associated with significant morbidity and early mortality. Available evidence in Asian populations shows that Hunter syndrome has a mean age of onset of 2 to 5 years and a life expectancy of 13 years in more severely affected individuals, with respiratory failure reported as the leading cause of death. Enzyme replacement therapy (ERT) with idursulfase (Elaprase, Shire Pharmaceuticals) and idursulfase beta (Hunterase, Green Cross Corp) are the only approved treatment for patients with MPS II. While these agents have the same amino acids, they have different glycosylation patterns because they are produced in different cell lines via different manufacturing processes. In previous studies, the beneficial effects of idursulfase beta have been confirmed in patients up to 35 years of age, without serious treatment-related safety concerns. The major drawbacks associated with ERT include the potential development of serious infusion-related anaphylactic reactions and up to 50% of treated patients develop anti-IDS antibodies. Here we report the case of a 13-year-old Malaysian patient with attenuated MPS II who developed troublesome infusion-associated reactions while receiving idursulfase treatment but tolerated and responded favorably to idursulfase beta.

The Carotid Intima-Media Thickness and Arterial Stiffness of Pediatric Mucopolysaccharidosis Patients Are Increased Compared to Both Pediatric and Adult Controls

Treatments for mucopolysaccharidoses (MPSs) have increased longevity, but cardiovascular disease causes mortality in a significant percentage of survivors. Markers must be developed to predict MPS cardiac risk and monitor efficacy of investigational therapies.MPS patients underwent carotid artery ultrasonography from which carotid intima-media thickness (cIMT) and three measures of arterial stiffness were calculated: carotid artery distensibility (cCSD), compliance (cCSC), and incremental elastic modulus (cIEM). MPS carotid measurements were compared to corresponding data from pediatric and adult healthy cohorts. 33 MPS patients (17 MPS I, 9 MPS II, 4 MPS IIIA, and 3 MPS VI; mean age 12.5 ± 4.7 years), 560 pediatric controls (age 13.1 ± 4.0 years), and 554 adult controls (age 39.2 ± 2.2 years) were studied. Age and sex-adjusted aggregate MPS cIMT (0.56 ± 0.05 mm) was significantly greater than both pediatric (+0.12 mm; 95% CI +0.10 to +0.14 mm) and adult (+0.10 mm; 95% CI +0.06 to +0.14 mm) control cohorts; similar findings were observed for all MPS subtypes. Mean MPS cIMT approximated the 80th percentile of the adult cohort cIMT. MPS patients also demonstrated significantly increased adjusted arterial stiffness measurements, evidenced by reduced cCSD, cCSC, and increased cIEM, compared to pediatric and adult control cohorts. Regardless of treatment, MPS patients demonstrate increased cIMT and arterial stiffness compared to healthy pediatric and adult controls. These data suggest that relatively young MPS patients demonstrate a “structural vascular age” of at least 40 years old.