Mucopolysaccharidosis type I in Morocco: clinical features and genetic profile]

BACKGROUND: Mucopolysaccharidoses (MPS) are inherited metabolic disorders due to lysosomal enzyme deficiencies, leading to glycosaminoglycan accumulation in lysosomes of different tissues. The aim of this study was to characterize MPS types, particularly MPS I, which are difficult to differentiate by clinical features. PATIENTS AND METHODS: Over a period of three years (June 1996-May 1999), 16 Moroccan patients (3-20 years old) with MPS were investigated. Twelve of them came from the Souss region. In subjects with suspected clinical MPS I or II, the diagnosis was confirmed by biochemical investigations, which included the quantification of total glycosaminoglycans (GAGs) released in urine, their identification, and the assay of alpha-L-iduronidase activity in leucocytes. A molecular analysis was performed in parallel, to provide the genetic proof of the diagnosis. RESULTS: These 16 patients belonged to 12 families, nine of which were consanguineous (75%). Twelve patients had Hurler syndrome and three had Hurler/Scheie's syndrome; no case of Scheie's syndrome was observed. Short stature, coarse face, organomegaly, hernia, cardiac disease, mental delay and dysostosis were observed in variable degrees. We report three cases without corneal clouding. Increased total urinary GAGs, identified as dermatan sulfate and heparan sulfate by thin-layer chromatography and total deficiency of alpha-L-iduronidase activity, were noted in studied subjects. At the molecular level the P533R mutation was detected in 24 among 26 alleles studied. CONCLUSION: It is now possible to perform the screening of MPS I and II in Morocco by analysis of clinical, radiologic observations and biological investigation. The predominance of P533R mutation could permit the screening of healthy heterozygotes and genetic counselling for families of Moroccan descent.     

Cardiac and ocular pathologies in a mouse model of mucopolysaccharidosis type VI

Mucopolysaccharidosis type VI (MPS VI) is a lysosomal storage disease caused by a deficiency of arylsulfatase B (ASB) which has its function in the sequential degradation of glycosaminoglycans (GAG). Targeted disruption of the ASB gene resulted in a mouse model of MPS VI that has been closely investigated for skeletal and chondral dysplasia. As ocular and cardiac impairment are also clinically important manifestations of the MPS VI syndrome, the present study was initiated for detailed biochemical, histologic and functional analysis of cornea, optic nerve and heart in ASB-deficient mice. Biochemical evidence for GAG-storage could be obtained for liver, kidney, spleen and myocardium as well as for heart valves, cornea and optic nerve from ASB-deficient mice. In MPS VI mice, histology revealed structural impairment of corneal stroma and epithelium as well as a thickening of the heart valves. According to histologic investigations, the optic nerve appeared not to be altered. However, GAG-storage in the dura mater could be demonstrated in MPS VI mice. Heart function was assessed by echocardiography. While the dimensions of MPS VI hearts were not altered, these hearts clearly showed decreased myocardial contraction and a 50% reduction of cardiac output. In addition, insufficiencies in the mitral and aortic valves were detected. Thus, ASB-deficient mice resemble the phenotype of human MPS VI not only in the skeletal but also in the ocular and cardiac symptoms. To our knowledge, these in vivo evaluations of heart function represent the first respective investigation of a MPS VI animal model and should provide a valuable measure for therapy studies in the MPS VI mouse.     

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.     

Clinical, pathological and molecular genetic findings in a case of neonatal Marfan syndrome

An infant with neonatal Marfan syndrome is described who presented with arachnodactyly, distinctive dysmorphic features and prolapse of both atrioventricular valves and dilatation of both the aortic and pulmonary root. She died in cardiac failure shortly after pacemaker implantation, due to dysrhythmia and severe mitral insufficiency. At autopsy, apart from myxomatous changes of the valves and dilated aortic and pulmonary roots, an aneurysm of the sinus of Valsalva of the pulmonary valve and abnormal myxomatous connective tissue surrounding the AV node were also found. Molecular genetic studies showed a point mutation in the fibrillin 1 gene that creates a new N-glycosylation site, which has been described once before.     

Mitral and aortic regurgitation in 84 patients with mucopolysaccharidoses

In echocardiographic and necropsy studies nodular thickening of the mitral valve and, less frequently, of the aortic valve has been found in 60%–90% of patients with mucopolysaccharidoses (MPS). Little is known about the haemodynamic consequences of these morphological changes. In this study 84 unselected patients with different enzymatically proven MPS and 84 age and sex matched, healthy persons were studied prospectively by colour Doppler flow mapping. The patients' age ranged from 1 to 47 years (median 8.1 years). Mitral and aortic regurgitation were defined as a holosystolic or holodiastolic jet originating from the valve into the left atrium or the left ventricular outflow tract, respectively, with peak velocities exceeding 2.5 m/s. Of the 84 patients with satisfactory studies, mitral regurgitation was detected in 64.3% and aortic regurgitation in 40.5%, respectively. Regurgitation was severe in 4.8% of mitral valves and 8.3% of aortic valves. The frequency of aortic and/or mitral regurgitation was 75% in all patients, 89% in MPS I, 94% in MPS II, 66% in MPS III, 33% in MPS IV, and 100% in MPS VI. Combined mitral and aortic regurgitation was present in 29% of our patients. None of the control persons showed mitral or aortic regurgitation.     

Thrombus Formation in the Native Aortic Root in Patients with Hypoplastic Left Heart Syndrome

Thrombus formation in the native aortic root is a rare but potentially life-threatening complication in patients with hypoplastic left heart syndrome. The native aortic root in these patients serves as a conduit for the retrograde filling of the coronary arteries. Thrombus in this location could result in myocardial ischemia. We present three cases of native aortic root thrombosis at our institution with clinical presentations ranging from asymptomatic to sudden cardiac arrest. Our experience with these patients argues for careful and consistent evaluation of the native aortic root regardless of clinical symptoms.     

Sudden Death in Supravalvular Aortic Stenosis: Fusion of a Coronary Leaflet to the Sinus Ridge, Dysplasia and Stenosis of Aortic and Pulmonic Valves

Supravalvular aortic stenosis (SVAS) is an uncommon congenital cardiac anomaly. We report sudden death, occurring during exercise, of a child who had SVAS with fusion of the right coronary aortic leaflet to the supravalvular aortic ridge, resulting in a closed sinus of Valsalva except for a few pinpoint fenestrations in the dysplastic leaflet. In addition, both aortic and pulmonic valves were dysplastic and stenotic. We postulate that near total isolation of the right coronary artery ostium from the aortic lumen compromised the blood supply to the hypertrophied ventricles. We emphasize the importance of other cardiac anomalies associated with SVAS as well as the development of coronary insufficiency.     

Quadrivalvar Replacement in Infantile Marfan Syndrome

Marfan syndrome (MS) is a connective tissue disease involving the cardiovascular, ocular, and the musculoskeletal systems. MS has variable phenotypic expression and is most often diagnosed in adult life. Infantile-onset MS is rare and is associated with severe cardiovascular manifestations; there is an extremely high mortality during the first 2 years of life. We present a case of a child with severe infantile MS who, during the course of infancy and early childhood, developed aortic root dilatation and polyvalvar insufficiency requiring subsequent successful replacement of the aortic root and of all cardiac valves. To our knowledge, this is the first reported case of quadrivalvar replacement in the pediatric age group.     

Combined enzyme replacement and haematopoietic stem cell transplantation in Hurler syndrome

We report the long-term follow-up of successful treatment of mucopolysaccharidosis type I H (MPS IH, Hurler syndrome) with combined enzyme replacement therapy and haematopoietic progenitor stem cell transplant.     

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.     

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.     

Hematopoietic stem cell transplantation effects on spinal cord compression in Hurler

Hurler syndrome type 1 (MPS‐1) is an autosomal recessive lysosomal disorder due to the deficiency of the enzyme alpha‐L‐iduronidase which is necessary for the degradation of dermatan and heparan sulfate. It is characterized by deposit of glycosaminoglycans in tissues, progressive multisystem dysfunction, and early death. HSCT for children with MPS‐I is effective, resulting in increased life expectancy and improvement of clinical parameters. The spinal MRI performed on a female 10 yr old undergoing HSCT at the age of 18 months and receiving ERT revealed a considerable decrease in soft tissue around the tip of odontoid causing a significant reduction in spinal cord compression. In light of this result, we suppose that combined ERT and HSCT are successful in Hurler I disease.     

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.     

Absent Aortic and Dysplastic Pulmonary Valves Associated with Ventricular Septal Defect in Fetal Hydrops

We describe worsening cardiac failure in a hydropic male fetus with a large ventricular septal defect associated with severe pulmonary and mild aortic regurgitation detected prenatally by echocardiography. The hemodynamic transition after emergency cesarean section at 31 weeks of gestation resulted in amelioration of the pulmonary incompetence but exacerbation of aortic insufficiency causing coronary steal. Death followed withdrawal of support 4 hours after delivery. Autopsy revealed absent aortic valve cusps, dysplastic pulmonary valve, and a large ventricular septal defect.     

Persistent truncus arteriosus: Pathologic anatomy in 54 cases

Summary Fifty-four specimens of heart with persistent truncus arteriosus (PTA) were reviewed anatomically. According to the Collett-Edwards classification [11] there were 28 examples of type I and 26 type II. The sex distribution was equal. The number of the truncal cusps ranged from one to four (42% tricuspid, 30% bicuspid, 24% quadricuspid, and 4% unicommissural). A unicommissural truncal valve has not been previously reported. In 72% of cases, the truncal valve leaflets were thickened or dysplastic. Two valves were stenotic. The truncus arteriosus originated from both ventricles equally in 42% of the cases, predominantly from the right ventricle in 42%, and predominantly from the left ventricle in 16% of the cases. In unoperated cases of PTA originating predominantly from the right ventricle, it appeared to us that usual operative correction might result in left ventricular outflow obstruction. Variations in coronary arterial origins and patterns were present in nearly half of the cases. A single coronary artery was observed in ten cases (18.5%). Stenosis of the ostium of one coronary artery was seen in each of four cases (7%). High posterior origin of the left coronary artery was observed in ten cases (18.5%). Among the associated cardiovascular anomalies, the most common were right aortic arch (36%) and interruption of the aortic arch (11%). Three cases with the latter condition exhibited crossed pulmonary arteries. Isolated cases with tricuspid atresia, vascular sling (left pulmonary artery arising from right pulmonary artery), and persistent common atrioventricular canal were encountered.     

Idiopathic Hyperammonemia following an Unrelated Cord Blood Transplant for Mucopolysaccharidosis I

Bone marrow transplantation (BMT) has been shown to reverse or stabilize some manifestations of mucopolysaccharidosis I (Hurler syndrome). Idiopathic hyperammonemia (IHA) is a rare complication of solid organ and BMT that is characterized by elevated serum ammonia, normal liver enzymes, and abrupt onset of neurologic deterioration. We present the case of a 14-month-old male patient with Hurler syndrome who developed fatal IHA (ammonia = 2297 mmol/L) 31 days after a cord blood transplant. A complete autopsy was performed, with examination of both frozen and formalin-fixed paraffin-embedded (FFPE) tissues using a variety of special stains and electron microscopy. Hyperammonemia was documented by analysis of antemortem serum and postmortem cerebrospinal and vitreous fluid. Other causes of hyperammonemia, including Reye syndrome, were excluded. Histologic changes included centrilobular microvesicular steatosis of the liver and storage product present in multiple organs. The highly water-soluble mucopolysaccharide (MPS) storage product was best identified by colloidal iron staining of FFPE and unfixed air-dried fresh frozen liver sections. Alcian blue stains failed to convincingly demonstrate MPS in any of the liver sections. This is the first published report, to our knowledge, of IHA in a posttransplant patient younger than 18 years old or following transplantation for Hurler syndrome. Demonstration of the hepatic centrilobular microvesicular steatosis characteristic of IHA was complicated by the diffuse storage of MPS within the liver. MPS storage can be best detected in the liver using colloidal iron staining. Oil-red-O staining may be useful to document microvesicular steatosis in cases with a clinical history of hyperammonemia following solid organ or BMT. Determining if certain subsets of children are at increased risk for IHA requires further study.     

Cardiovascular changes in children with mucopolysaccharide disorders

The aims of this study were to evaluate cardiac involvement, assess risk factors and mortality, and define the outcome of cardiac abnormalities with age in the different types of mucopolysaccharidoses (MPS). The echocardiograms of 99 patients with MPS, aged 1-24 y (median age 10.3 y) were reviewed between 1978 and 2000. Mitral regurgitation (MR) was detected in 29 patients (29%). MR was more frequent in types IH [ n = 11 (38%)], II [ n = 10 (24%)] and III [ n = 4 (20%)]. Sixteen patients (16%) developed aortic regurgitation (AR), seen mostly in types II [ n = 9 (56%)] and IV [ n = 4 (24%)]. AR and/or MR was detected in 37 patients and 8 had both abnormalities of borderline significance (odds ratio 2.95, 95% confidence interval 1.0-8.85, p = 0.05). Of 99 patients, 47 had a normal study on their first echocardiogram, whereas only 7 had a normal study on subsequent echocardiograms. Fifty-four (54%) had a single echocardiogram. Of these, 27 (50%) were abnormal and 27 normal. Forty-five patients had more than one echocardiogram, of which 25 (56%) were abnormal and 20 normal. In 13/20 (65%) a cardiac abnormality developed on a subsequent echocardiogram which was statistically significant ( p = 0.002). Overall mitral and aortic valve abnormalities showed a positive association with age. Univariate analysis of risk factors showed that increasing age, MPS I and ejection fraction were significant risk factors for death. However, left ventricular hypertrophy, mitral valve abnormalities and type II MPS were not significant risk factors for death, with borderline significance for aortic valve abnormalities.

Conclusion: This study demonstrates the evaluation of ventricular function, which is a significant risk factor for death, along with increasing age and MPS I, and outlines the borderline significance of aortic valve abnormalities, which has not been mentioned in previous studies. It also shows that mitral valve lesions, commonly seen in MPS, were not a significant risk factor for death. The results emphasize the importance of performing serial echocardiograms in patients with MPS to assess ventricular function and the progression of cardiac abnormalities with age.     

Incidence and prevalence of mucopolysaccharidosis type 1 in the Irish republic

Mucopolysaccharidosis type 1 (MPS1) is an autosomal recessive disorder with severe, moderate and mild phenotypes: Hurler, Hurler-Scheie and Scheie syndromes. We estimated incidence (2001-2006) and prevalence (2002 census) of MPS1 in the Irish Republic (ROI) using population data, database and chart review of all live MPS1 patients attending two specialised centres. Patient genotypes, ethnicity, province of origin, age at diagnosis and presenting features were recorded. Thirty-one patients (14 females, 17 males) were alive, 27 of whom were <15 years. Twenty-six patients had Hurler syndrome, four had Hurler-Scheie and one had Scheie syndrome. The birth incidence was 1 in 26 206 births with a carrier frequency of 1 in 81. Of note, 19/26 (73%) Hurler patients were Irish Travellers. Amongst Irish Travellers the incidence was 1 in 371 with a carrier frequency of 1 in 10. This is the highest recorded incidence worldwide. Given the morbidity and mortality associated with delayed treatment we recommend targeted newborn screening for this population.     

Pulmonary atresia, intact ventricular septum, right ventricle-dependent coronary artery circulation, and systemic collateral arteries supplying the left coronary artery.

We present a 14-day-old with pulmonary artery atresia with intact ventricular septum, right ventricle-dependent coronary circulation, a single aortic root coronary ostia (left), congenital collateral arterial supply to the left coronary artery from the left internal mammary artery, and bilateral paravertebral arteries, with obstructive coronary artery lesions.     

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.