Cardiac abnormalities in adults with the attenuated form of mucopolysaccharidosis type I

Natural history of cardiac findings in mucopolysaccharidosis type I: report from an international registry

Mucopolysaccharidosis type I is an inborn error of glycosaminoglycan catabolism with phenotypes ranging from severe (Hurler syndrome) to attenuated (Hurler-Scheie and Scheie syndromes). Cardiovascular involvement is common and contributes significantly to morbidity and mortality. We conducted a retrospective analysis of the prevalence and natural history of cardiac abnormalities in treatment-naïve individuals enrolled in the international Mucopolysaccharidosis Type I Registry. Interrogation of echocardiography data (presence of cardiac valve regurgitation and/or stenosis; measurements of left ventricular chamber dimensions in diastole and systole, diastolic left ventricular posterior wall and interventricular septal thicknesses and ventricular systolic function (shortening fraction)) showed that mitral regurgitation was the most common and earliest finding for individuals with both severe (58.3%, median age 1.2 years) and attenuated (74.2%, median age 8.0 years) disease. Left-sided valve stenosis was also common in individuals with attenuated disease (mitral 30.3%; aortic 25%). Abnormal ventricular wall and septal thickness (Z-scores ≥2) were observed early in both phenotypes. Z-scores for diastolic left ventricular posterior wall and interventricular septal thicknesses increased with age in the severe phenotype (annualised slopes of 0.2777 [p = 0.037] and 0.3831 [p = 0.001], respectively); a similar correlation was not observed in the attenuated phenotype (annualised slopes of -0.0401 [p = 0.069] and -0.0029 [p = 0.875], respectively). Decreased cardiac ventricular systolic function (defined as shortening fraction <28%) was uncommon but, when noted, was more frequent in infants with the severe phenotype. While cardiac abnormalities occur early in both severe and attenuated mucopolysaccharidosis type I, the pattern of valve dysfunction and progression of ventricular abnormalities vary by phenotype.

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.

Quantification of Idua Enzymatic Activity Combined with Observation of Phenotypic Change in Zebrafish Embryos Provide a Preliminary Assessment of Mutated idua Correlated with Mucopolysaccharidosis Type I

Mucopolysaccharidosis type I (MPS I) is an inherited autosomal recessive disease resulting from mutation of the α-l-Iduronidase (IDUA) gene. New unknown mutated nucleotides of idua have increasingly been discovered in newborn screening, and remain to be elucidated. In this study, we found that the z-Idua enzymatic activity of zebrafish idua-knockdown embryos was reduced, resulting in the accumulation of undegradable metabolite of heparin sulfate, as well as increased mortality and defective phenotypes similar to some symptoms of human MPS I. After microinjecting mutated z-idua-L346R, -T364M, -E398-deleted, and -E540-frameshifted mRNAs, corresponding to mutated human IDUA associated with MPS I, into zebrafish embryos, no increase in z-Idua enzymatic activity, except of z-idua-E540-frameshift-injected embryos, was noted compared with endogenous z-Idua of untreated embryos. Defective phenotypes were observed in the z-idua-L346R-injected embryos, suggesting that failed enzymatic activity of mutated z-Idua-L346R might have a dominant negative effect on endogenous z-Idua function. However, defective phenotypes were not observed in the z-idua-E540-frameshifted-mRNA-injected embryos, which provided partial enzymatic activity. Based on these results, we suggest that the z-Idua enzyme activity assay combined with phenotypic observation of mutated-idua-injected zebrafish embryos could serve as an alternative platform for a preliminary assessment of mutated idua not yet characterized for their role in MPS I.

Delivering gene therapy for mucopolysaccharide diseases

Mucopolysaccharide diseases are a group of paediatric inherited lysosomal storage diseases that are caused by enzyme deficiencies, leading to a build-up of glycosaminoglycans (GAGs) throughout the body. Patients have severely shortened lifespans with a wide range of symptoms including inflammation, bone and joint, cardiac, respiratory and neurological disease. Current treatment approaches for MPS disorders revolve around two main strategies. Enzyme replacement therapy (ERT) is efficacious in treating somatic symptoms but its effect is limited for neurological functions. Haematopoietic stem cell transplant (HSCT) has the potential to cross the BBB through monocyte trafficking, however delivered enzyme doses limit its use almost exclusively to MPSI Hurler. Gene therapy is an emerging therapeutic strategy for the treatment of MPS disease. In this review, we will discuss the various vectors that are being utilised for gene therapy in MPS as well as some of the most recent gene-editing approaches undergoing pre-clinical and clinical development.

Mucopolysaccharidosis Type I Diagnosed by Aortic and Mitral Valve Replacement

A 32-year-old developmentally delayed man presenting with dyspnea was found to have severe aortic and mitral valve stenosis. After double valve replacement, unique histologic findings prompted a genetics evaluation, ultimately leading to the diagnosis of mucopolysaccharidosis type I, a rare lysosomal storage disorder with high rates of cardiac manifestations. (Level of Difficulty: Advanced.).

Neonatal nonviral gene editing with the CRISPR/Cas9 system improves some cardiovascular, respiratory, and bone disease features of the mucopolysaccharidosis I phenotype in mice

Mucopolysaccharidosis type I (MPS I) is caused by deficiency of alpha-L-iduronidase (IDUA), leading to multisystemic accumulation of glycosaminoglycans (GAG). Untreated MPS I patients may die in the first decades of life, mostly due to cardiovascular and respiratory complications. We previously reported that the treatment of newborn MPS I mice with intravenous administration of lipossomal CRISPR/Cas9 complexes carrying the murine Idua gene aiming at the ROSA26 locus resulted in long-lasting IDUA activity and GAG reduction in various tissues. Following this, the present study reports the effects of gene editing in cardiovascular, respiratory, bone, and neurologic functions in MPS I mice. Bone morphology, specifically the width of zygomatic and femoral bones, showed partial improvement. Although heart valves were still thickened, cardiac mass and aortic elastin breaks were reduced, with normalization of aortic diameter. Pulmonary resistance was normalized, suggesting improvement in respiratory function. In contrast, behavioral abnormalities and neuroinflammation still persisted, suggesting deterioration of the neurological functions. The set of results shows that gene editing performed in newborn animals improved some manifestations of the MPS I disorder in bone, respiratory, and cardiovascular systems. However, further studies will be imperative to find better delivery strategies to reach "hard-to-treat" tissues to ensure better systemic and neurological effects.

General Anesthesia Management for Adult Mucopolysaccharidosis Patients Undergoing Major Spine Surgery

OBJECTIVE

Mucopolysaccharidosis (MPS) are a group of rare systemic lysosomal storage diseases associated with severe airway obstruction and cardiac disease, making anesthesia management difficult. Contemporary treatment extends the lifespan of affected individuals, increasing the need for major surgery in adulthood.

CLINICAL PRESENTATION AND INTERVENTION

We provided general anesthesia for 6 adult MPS patients undergoing spine surgery. The airway was assessed as difficult in all, with 2 receiving awake fiberoptic intubation and 1 successfully undergoing video-laryngoscopy, while 3 video-laryngoscopy procedures failed and required conversion to fiberoptic intubation. One patient developed ventricular fibrillation.

CONCLUSION

Adult MPS patients have substantial anesthesia risk.

Lysosomal storage disorders affecting the heart: a review

Lysosomal storage disorders (LSD) comprise a group of diseases caused by a deficiency of lysosomal enzymes, membrane transporters or other proteins involved in lysosomal biology. Lysosomal storage disorders result from an accumulation of specific substrates, due to the inability to break them down. The diseases are classified according to the type of material that is accumulated; for example, lipid storage disorders, mucopolysaccharidoses and glycoproteinoses. Cardiac disease is particularly important in lysosomal glycogen storage diseases (Pompe and Danon disease), mucopolysaccharidoses and in glycosphingolipidoses (Anderson-Fabry disease). Various disease manifestations may be observed including hypertrophic and dilated cardiomyopathy, coronary artery disease and valvular diseases. Endomyocardial biopsies can play an important role in the diagnosis of these diseases. Microscopic features along with ancillary tests like special stains and ultrastructural studies help in the diagnosis of these disorders. Diagnosis is further confirmed based upon enzymatic and molecular genetic analysis. Emerging evidence suggests that Enzyme replacement therapy (ERT) substantially improves many of the features of the disease, including some aspects of cardiac involvement. The identification of these disorders is important due to the availability of ERT, the need for family screening, as well as appropriate patient management and counseling.

The factors affecting lipid profile in adult patients with Mucopolysaccharidosis

Background

Mucopolysaccharidoses (MPS) are a group of rare inherited disorders characterized by abnormal accumulation of glycosaminoglycans (GAGs) within the myocytes and coronary arteries. Little is known about hyperlipidaemia as a potential cardiovascular risk factor in these patients. Baseline cholesterol data in adults are scarce. Therefore, the aim of this study was to analyse factors affecting lipid profile in different types of MPSs to determine if abnormalities in lipid profile contribute to the overall risk of cardiovascular disease.

Methods

Adult patients (above the age of 16) with MPS type I, II, III, IV and VI attending clinics in two Inherited Metabolic Disorders centres were included. Their lipid profile, lipoprotein (a), HbA1c, Glucose Tolerance Test (GTT), BMI and treatment type were extracted. Analysis included descriptive statistics and Student t-test.

Results

Eighty two patients with five MPS types (I, II, III, IV and VI) were included in the study; 29 were females (35%) and 53 were males (65%). BMI above 25 kg/m² in all MPS types indicated that some patients were overweight for their height. Only one patient post-HSCT had diabetes. In 3 cases insulin was analysed during GTT and showed no insulin resistance despite raised BMI. Mean total cholesterol and LDL-cholesterol were below 5 mmol/L and 3 mmol/L, respectively, in five individual MPS types. Lipoprotein (a) was available for 6 MPS IV patients and was not significantly raised.

Conclusions

MPS disorders are not associated with significant hypercholesterolaemia or diabetes mellitus despite increased BMI. Total cholesterol and LDL-cholesterol were within the targets for primary prevention for non-MPS population. Lipoprotein (a) is not a useful marker of cardiovascular disease in a small group of adult MPS IV patients irrespectively of treatment option. Whether long-term cardiovascular risk is dependent on lipid profile, diabetes, obesity or GAGs deposition within the organ system remains unanswered.

Outcomes of Long-Term Treatment with Laronidase in Patients with Mucopolysaccharidosis Type I

OBJECTIVE

To evaluate long-term outcomes of laronidase enzyme replacement therapy in patients with attenuated mucopolysaccharidosis type I.

STUDY DESIGN

Retrospective analyses of case notes, laboratory results, and data from clinical trials were used to evaluate urinary glycosaminoglycans, forced vital capacity (FVC), 6-minute walk test (6MWT), height-for-age Z score, cardiac valve function, corneal clouding, and visual acuity in 35 patients with attenuated mucopolysaccharidosis type I (Hurler-Scheie and Scheie syndromes) for up to 10 years following the initiation of laronidase therapy.

RESULTS

Statistically significant (P < .001) reductions in mean urinary glycosaminoglycan levels relative to baseline were observed 6 months after treatment initiation and were sustained throughout follow-up. Disease remained stable after treatment initiation with no statistically significant changes in mean FVC, 6MWT, or height-for-age Z score. At last assessments, mitral and aortic valve function remained stable in 65% (22/34) of patients; corneal clouding remained stable in 78% (18/23); visual acuity remained stable in 33% (8/24) and improved in 42% (10/24) of patients. Younger patients (<10 years at treatment initiation) maintained disease measures closer to norms for age for FVC, 6MWT, and height and showed fewer deteriorations in mitral and aortic valve disease and corneal clouding compared with patients aged ≥10 years at treatment initiation.

CONCLUSION

Laronidase treatment resulted in disease stabilization in the majority of patients with a mean follow-up of 6.1 years. Data suggest that early treatment may result in better outcomes.

Decreased performance in IDUA knockout mouse mimic limitations of joint function and locomotion in patients with Hurler syndrome

BACKGROUND

Mucopolysaccharidosis type I (MPS I) is caused by the deficiency of alpha-L-iduronidase (IDUA), which is involved in the degradation of glycosaminoglycans (GAGs), such as heparan sulfate and dermatan sulfate in the lysosome. It has been reported that joint symptoms are almost universal in MPS I patients, and even in the case of attenuated disease, they are the first symptom that brings a child to medical attention. However, functional tests and biological markers have not been published for the evaluation of the limitations in joint and locomotion in animal model-mimicking MPS.

METHODS

We generated IDUA knockout (KO) mice to observe whether they present impairment of joint function. KO mice were characterized phenotypically and tested dual-energy X-ray absorptiometry analysis (DEXA), open-field, rotarod, and grip strength.

RESULTS

The IDUA KO mice, generated by disruption between exon 6 and exon 9, exhibited clinical and laboratory findings, such as high urinary GAGs excretion, GAGs accumulation in various tissues, and significantly increased bone mineral density (BMD) in both female and male mice in the DEXA of the femur and whole bone. Remarkably, we observed a decrease in grasp function, decreased performance in the rotarod test, and hypo-activity in the open-field test, which mimic the limitations of joint mobility and decreased motor performance in the 6-min walk test in patients with MPS I.

CONCLUSIONS

We generated a new IDUA KO mouse, tested open field, rotarod and grip strength and demonstrated decrease in grip strength, decreased performance and hypo-activity, which may be useful for investigating therapeutic approaches, and studying the pathogenesis of joint and locomotion symptoms in MPS I.

Laronidase replacement therapy and left ventricular function in mucopolysaccharidosis I

We assessed the effects of long-term laronidase replacement therapy (LRT) on the left ventricular (LV) function of a 52-year-old adult woman with mucopolysaccharidosis I (MPS I). The urinary uronic acid concentration significantly decreased by 78.7% (from 75 to 16 mg/g creatinine) after LRT; thereafter, estimated LV weight as assessed by two-dimensional (2D) echocardiography significantly decreased by 33.3% (from 189 to 126 g). Although systolic LV function of the ejection fraction as assessed by 2D echocardiogram did not change after LRT, the diastolic LV function parameters of the deceleration time (DcT) and the ratio of early (E) to late (A) ventricular filling velocities (E/A ratio) significantly improved. The DcT significantly decreased from 355 to 300 ms and the E/A ratio significantly decreased from 1.8 to 0.98. These diastolic parameters were normalized. In the contraction synchrony assessed by 2D speckle tracking imaging, the maximum time delay of contraction decreased from 148 to 14 ms. In addition, the LV weight significantly correlated with the E/A ratio (p < 0.001, r = 0.63), DcT (p < 0.05, r = 0.48), and contraction synchrony (p < 0.001, r = 0.61), respectively. This is the first study to report that LRT significantly improves diastolic LV function and contraction synchrony in a patient with MPS I.

Unexpected coronary artery findings in mucopolysaccharidosis. Report of four cases and literature review

INTRODUCTION

The mucopolysaccharidosis syndromes are a group of lethal inherited disorders affecting multiple organ systems by the progressive deposition of glycosaminoglycan. Advances in treatment such as enzyme replacement and hematopoietic stem cell transplantation have significantly improved the outcome of these disorders. An in-depth understanding of the pathophysiology of heart disease in these disorders is essential since death from cardiac causes continues to be common. Epicardial coronary artery luminal narrowing from myointimal proliferation and glycosaminoglycan deposition is well described in severe mucopolysaccharidosis type I [Hurler syndrome, mucopolysaccharide IH] but poorly understood in other "non-Hurler" phenotypes of these disorders. Given the rarity of these conditions, autopsy specimens are uncommon.

METHODS

Tissue from epicardial coronary arteries from autopsies of four patients with non-Hurler mucopolysaccharidosis (attenuated type I, type IIIA, type IIIC, and type VI) who had died after hematopoietic cell transplantation (within 1 month in three cases; after 5 years in the fourth) was examined by light microscopy.

RESULTS

Unexpectedly, near-normal coronary arteries were observed in the patient with attenuated mucopolysaccharidosis type I, while the coronaries from patients with type IIIA, IIIC, and VI demonstrated classic histologic features of glycosaminoglycan deposition. The most severe findings were found in the MPS IIIC patient who had 5 years of full donor engraftment after transplantation.

CONCLUSIONS

Our current understanding of the cardiac manifestations of the mucopolysaccharidoses fails to explain why near-normal coronary arteries may be observed when abnormalities would be most likely to be expected and, conversely, why significant histopathology is present when it would be least expected. Identification of downstream effects of glycosaminoglycan deposition may identify other metabolites or metabolic pathways that are important in the clinicopathologic manifestations of these diseases.

SUMMARY

The mucopolysaccharidosis diseases are a group of inherited disorders affecting multiple organ systems by the progressive deposition of glycosaminoglycan. Severe coronary artery disease is well recognized in severe type I mucopolysaccharidosis (Hurler syndrome), but unexpected coronary artery disease occurs in other, "non-Hurler" mucopolysaccharidoses. Factors responsible for the development of coronary pathology in the mucopolysaccharidoses remain elusive.

Isokinetic muscle strength differences in patients with mucopolysaccharidosis I, II, and VI

PURPOSE

To determine muscular strength differences in patients with MPS-I, II, and VI versus age- and sex-matched healthy controls.

METHODS

Dominant leg isokinetic knee extension strength was measured at 90 and 120 degrees per second (d/s) using a dynamometer in 30 subjects with MPS and 42 controls (5-16 yrs). MPS-I was further divided into MPS-IA (attenuated) and MPS-IH (severe). Strength measures analyzed were peak torque (PkT), peak torque per unit body weight (PkT/BW) and per unit lean body mass (PkT/LBM), and average power (AP).

RESULTS

Following adjusting strength measures for age, MPS-IH and MPS-II had significantly lower strength measures for all variables at both angular velocities. MPS-VI had significantly lower PkT, PkT/LBM, and AP compared to controls at 90 and 120d/s. In contrast, MPS-IA was not significantly different from controls for any strength variable at either angular velocity.

CONCLUSION

The results of this study suggest that decrements in skeletal muscle strength depend on MPS diagnosis and severity of disease. Children with MPS-IH demonstrate the greatest difference in muscular strength compared to healthy controls.

The effect of neonatal gene therapy with a gamma retroviral vector on cardiac valve disease in mucopolysaccharidosis VII dogs after a decade

Mucopolysaccharidosis VII (MPS VII) is due to deficient activity of the lysosomal enzyme β-glucuronidase (GUSB) and results in the accumulation of glycosaminoglycans (GAGs). This study determined the long-term effect of neonatal intravenous injection of a gamma retroviral vector (RV) on cardiac valve disease in MPS VII dogs. Transduced hepatocytes secreted GUSB into the blood for up to 11 years at levels similar to or greater than those achieved with enzyme replacement therapy (ERT). Valve regurgitation and thickening were scored from 0 (normal) to +4 (severely abnormal). At 1 year, untreated MPS VII dogs had mitral regurgitation, mitral valve thickening, aortic regurgitation, and aortic valve thickening scores of 2.3 ± 0.7, 2.3 ± 0.6, 1.8 ± 0.5, and 1.6 ± 0.7, respectively, which were higher than the values of 0.6 ± 0.1, 0.1 ± 0.4, 0.3 ± 0.8, and 0.1 ± 0.4, respectively, in treated MPS VII dogs. Treated MPS VII dogs maintained low aortic regurgitation and aortic valve thickening scores in their lifetime. Although mitral regurgitation and mitral valve thickening scores increased to 2.0 at ≥ 8 years of age in the treated MPS VII dogs, older normal dogs from the colony had similar scores, making it difficult to assess mitral valve disease. Older treated dogs had calcification within the mitral and the aortic valve annulus, while GUSB staining demonstrated enzyme activity within the mitral valve. We conclude that neonatal RV-mediated gene therapy reduced cardiac valve disease in MPS VII dogs for up to 11 years, and propose that neonatal initiation of ERT should have a similar effect.

Genetics and metabolic cardiomyopathies

Metabolic disorders encompass a heterogeneous group of conditions that commonly affect the heart and contribute adversely to cardiovascular outcomes. As the heart is a metabolically active organ, inborn errors in metabolism (IEMs) often present with cardiac manifestations such as cardiomyopathy, arrhythmia, and valvular dysfunction. More than 40 IEMs are reported to cause cardiomyopathy, including fatty acid oxidation defects, glycogen, lysosomal and perioxisome storage diseases, mitochondrial cardiomyopathies, organic acidaemias, aminoacidopathies and congenital disorders of glycosylation. Studies suggest that IEM account for only 5% of cardiomyopathies; however, their diagnosis is imperative to enable the effective institution of disease-specific management strategies. This review describes the more common genetic defects that affect metabolic pathways and give rise to heart muscle disease.

Mucopolysaccharidosis type VI: a cardiologist's guide to diagnosis and treatment

Mucopolysaccharidosis type VI (MPS VI, Maroteaux-Lamy syndrome) is an inborn error of metabolism, with incidences at birth ranging from 1 in 1.5 million to 1 in 43,000 live births. This disorder is rarely considered when evaluating patients with common populational cardiovascular diseases. A significant number of MPS VI patients, however, do present cardiovascular disease and MPS VI should be considered as a potential differential diagnosis for other cardiovascular disorders. This article reviews the clinical features, diagnostic tests and treatment options for MPS VI. Although MPS VI affects many organs and systems of the human body this review focuses on MPS VI diseases of the heart and vessels. The most characteristic cardiac presentation of MPS VI is valvular disease, but heart failure, pulmonary hypertension, cardiomyopathy, fibroelastosis and cardiac conduction system disorders may also occur. Cardiovascular disease in MPS VI patients may emerge silently. An early diagnosis is difficult due to joint stiffness, respiratory system involvement or skeletal malformations that limit exercise capacity and mask the underlining heart failure. This article is supposed to serve as a very practical reference for cardiologists who may come across MPS VI in their daily practices. A greater awareness of cardiovascular manifestations of MPS VI among cardiologists can help to reduce misdiagnosis and promote early detection of this inborn disorder and aid the implementation of adequate therapy at the earliest stage possible which is crucial for its efficacy.

Cardiac disease in patients with mucopolysaccharidosis: presentation, diagnosis and management

The mucopolysaccharidoses (MPSs) are inherited lysosomal storage disorders caused by the absence of functional enzymes that contribute to the degradation of glycosaminoglycans (GAGs). The progressive systemic deposition of GAGs results in multi-organ system dysfunction that varies with the particular GAG deposited and the specific enzyme mutation(s) present. Cardiac involvement has been reported in all MPS syndromes and is a common and early feature, particularly for those with MPS I, II, and VI. Cardiac valve thickening, dysfunction (more severe for left-sided than for right-sided valves), and hypertrophy are commonly present; conduction abnormalities, coronary artery and other vascular involvement may also occur. Cardiac disease emerges silently and contributes significantly to early mortality.The clinical examination of individuals with MPS is often difficult due to physical and, sometimes, intellectual patient limitations. The absence of precordial murmurs does not exclude the presence of cardiac disease. Echocardiography and electrocardiography are key diagnostic techniques for evaluation of valves, ventricular dimensions and function, which are recommended on a regular basis. The optimal technique for evaluation of coronary artery involvement remains unsettled.Standard medical and surgical techniques can be modified for MPS patients, and systemic therapies such as hematopoietic stem cell transplantation and enzyme replacement therapy (ERT) may alter overall disease progression with regression of ventricular hypertrophy and maintenance of ventricular function. Cardiac valve disease is usually unresponsive or, at best, stabilized, although ERT within the first few months of life may prevent valve involvement, a fact that emphasizes the importance of early diagnosis and treatment in MPS.

Pathogenesis of aortic dilatation in mucopolysaccharidosis VII mice may involve complement activation

Mucopolysaccharidosis VII (MPS VII) is due to mutations within the gene encoding the lysosomal enzyme β-glucuronidase, and results in the accumulation of glycosaminoglycans. MPS VII causes aortic dilatation and elastin fragmentation, which is associated with upregulation of the elastases cathepsin S (CtsS) and matrix metalloproteinase 12 (MMP12). To test the role of these enzymes, MPS VII mice were crossed with mice deficient in CtsS or MMP12, and the effect upon aortic dilatation was determined. CtsS deficiency did not protect against aortic dilatation in MPS VII mice, but also failed to prevent an upregulation of cathepsin enzyme activity. Further analysis with substrates and inhibitors specific for particular cathepsins suggests that this enzyme activity was due to CtsB, which could contribute to elastin fragmentation. Similarly, MMP12 deficiency and deficiency of both MMP12 and CtsS could not prevent aortic dilatation in MPS VII mice. Microarray and reverse-transcriptase real-time PCR were performed to look for upregulation of other elastases. This demonstrated that mRNA for complement component D was elevated in MPS VII mice, while immunostaining demonstrated high levels of complement component C3 on surfaces within the aortic media. Finally, we demonstrate that neonatal intravenous injection of a retroviral vector encoding β-glucuronidase reduced aortic dilatation. We conclude that neither CtsS nor MMP12 are necessary for elastin fragmentation in MPS VII mouse aorta, and propose that CtsB and/or complement component D may be involved. Complement may be activated by the GAGs that accumulate, and may play a role in signal transduction pathways that upregulate elastases.

Mucopolysaccharidosis I, II, and VI: Brief review and guidelines for treatment

Mucopolysaccharidoses (MPS) are rare genetic diseases caused by the deficiency of one of the lysosomal enzymes involved in the glycosaminoglycan (GAG) breakdown pathway. This metabolic block leads to the accumulation of GAG in various organs and tissues of the affected patients, resulting in a multisystemic clinical picture, sometimes including cognitive impairment. Until the beginning of the XXI century, treatment was mainly supportive. Bone marrow transplantation improved the natural course of the disease in some types of MPS, but the morbidity and mortality restricted its use to selected cases. The identification of the genes involved, the new molecular biology tools and the availability of animal models made it possible to develop specific enzyme replacement therapies (ERT) for these diseases. At present, a great number of Brazilian medical centers from all regions of the country have experience with ERT for MPS I, II, and VI, acquired not only through patient treatment but also in clinical trials. Taking the three types of MPS together, over 200 patients have been treated with ERT in our country. This document summarizes the experience of the professionals involved, along with the data available in the international literature, bringing together and harmonizing the information available on the management of these severe and progressive diseases, thus disclosing new prospects for Brazilian patients affected by these conditions.

Echocardiographic study of paediatric patients with mucopolysaccharidosis

PRINCIPLE

Mucopolysaccharidosis is an inborn error of metabolism causing glucosaminoglycans tissue storage. Cardiovascular involvement is variable but contributes significantly towards the morbidity and mortality of the patients.

OBJECTIVE

To characterise the echocardiographic abnormalities in children and adolescents with different types of mucopolysaccharidosis.

METHOD

Echocardiograms and medical records of 28 patients aged 2-14 years, seen from 2003 to 2005, were revised. At that time, the enzymatic replacement therapy was still not available in our institution.

RESULTS

Echocardiographic alterations were detected in 26 patients (93%), whereas 16 (57%) had abnormal auscultation, and only 6 (21%) presented with cardiovascular complaint. Mitral valve thickening with dysfunction (regurgitation, stenosis, or double lesion) was diagnosed in 60.8%, left ventricular hypertrophy in 43% and aortic valve thickening with regurgitation in 35.8% of the patients. There was no systolic dysfunction and mild left diastolic dysfunction was shown in 21.5% of the patients. Pulmonary hypertension was present in 36% of the patients, causing the only two deaths recorded. There was a strong association between the accumulation of dermatan sulphate and the presence of mitral valve dysfunction (p = 0.0003), aortic valve dysfunction (p = 0.006), and pulmonary hypertension (p = 0.006). Among individuals with two or more examinations, 82% had a worsening evolution.

CONCLUSIONS

Echocardiographic alterations in children with Mucopolysaccharidosis are frequent and have a progressive character. Left valve lesions, ventricular hypertrophy, and pulmonary hypertension were the most common findings and there was an association between the accumulation of dermatan sulphate and cardiovascular involvement. Unlike in adults, pulmonary hypertension was the main cause of death, not left ventricle systolic dysfunction.

Upregulation of elastase activity in aorta in mucopolysaccharidosis I and VII dogs may be due to increased cytokine expression

Mucopolysaccharidosis I (MPS I) and MPS VII are due to loss-of-function mutations within the genes that encode the lysosomal enzymes alpha-l-iduronidase and beta-glucuronidase, respectively, and result in accumulation of glycosaminoglycans and multisystemic disease. Both disorders are associated with elastin fragmentation and dilatation of the aorta. Here, the pathogenesis and effect of gene therapy on aortic disease in canine models of MPS was evaluated. We found that cathepsin S is upregulated at the mRNA and enzyme activity level, while matrix metalloproteinase 12 (MMP-12) is upregulated at the mRNA level, in aortas from untreated MPS I and MPS VII dogs. Both of these proteases can degrade elastin. In addition, mRNA levels for the interleukin 6-like cytokine oncostatin M were increased in MPS I and MPS VII dog aortas, while mRNA for tumor necrosis factor alpha and toll-like receptor 4 were increased in MPS VII dog aortas. These cytokines could contribute to upregulation of the elastases. Neonatal intravenous injection of a retroviral vector expressing beta-glucuronidase to MPS VII dogs reduced RNA levels of cathepsin S and MMP-12 and aortic dilatation was delayed, albeit dilatation developed at late times after gene therapy. A post-mortem aorta from a patient with MPS VII also exhibited elastin fragmentation. We conclude that aortic dilatation in MPS I and MPS VII dogs is likely due to degradation of elastin by cathepsin S and/or MMP-12. Inhibitors of these enzymes or these cytokine-induced signal transduction pathways might reduce aortic disease in patients with MPS.