Skeletal phenotype amelioration in mucopolysaccharidosis VI requires intervention at the earliest stages of postnatal development.

Mucopolysaccharidosis VI (MPS VI) is a rare lysosomal disease arising from impaired function of the enzyme arylsulfatase B (ARSB). This impairment causes aberrant accumulation of dermatan sulfate, a glycosaminoglycan (GAG) abundant in cartilage. While clinical severity varies along with age at first symptom manifestation, MPS VI usually presents early and strongly affects the skeleton. Current enzyme replacement therapy (ERT) does not provide effective treatment for the skeletal manifestations of MPS VI. This lack of efficacy may be due to an inability of ERT to reach affected cells or to the irreversibility of the disease. To address the question of reversibility of skeletal phenotypes, we generated a conditional by inversion (COIN) mouse model of MPS VI, ArsbCOIN/COIN, wherein Arsb is initially null and can be restored to WT using Cre. We restored Arsb at different times during postnatal development, using a tamoxifen-dependent global Cre driver. By restoring Arsb at P7, P21, and P56-P70, we determined that skeletal phenotypes can be fully rescued if Arsb restoration occurs at P7, while only achieving partial rescue at P21 and no significant rescue at P56-P70. This work has highlighted the importance of early intervention in patients with MPS VI to maximize therapeutic impact.

The articular and the craniocervical abnormalities are of confusing age of onset in patients with Maroteaux-Lamy disease (MPS VI).

BACKGROUND: Maroteaux-Lamy disease (MPS Type VI) is an autosomal recessive lysosomal storage disorder. Skeletal abnormalities are vast. Early recognition may facilitate timely diagnosis and intervention, leading to improved patient outcomes. The most challenging is when patients manifest a constellation of craniocervical and articular deformities with variable age of onset. METHODS: We collected 15 patients with MPS VI (aged from 6 years-58 years). From within our practice in Pediatric Orthopedics, we present patients with MPS type VI who were found to manifest a diverse and confusing clinical presentation of hip deformities and cervical cord compression. Stem cell transplants were proposed as treatment tool and enzyme replacement therapy has been instituted in some patients. RESULTS: The spectrum of the clinical involvement in our group of patients was supported firstly via the clinical phenotype followed by assessment of the biochemical defect, which has been detected through the deficiency of N-acetylgalactosamine-4-sulfatase (arylsulphatase B) leading to increased excretion of dermatan sulphate. Secondly, through the molecular genetic results, which showed homozygous or compound heterozygous mutation in the ARSB gene on chromosome 5q14. Hip replacements and decompression operations have been performed to restore function and to alleviate pain in the former and life saving procedure in the latter. CONCLUSIONS: The efforts in searching for the etiological diagnosis in patients with skeletal dysplasia/MPSs has not been rewarding as many had anticipated. This emerged from several facts such as improper clinical documentation, missing diagnostic pointers in radiographic interpretations, limited knowledge in skeletal dysplasia and its variants, and the reliance on underpowered studies. Physicians and radiologists are required to appreciate and assess the diverse phenotypic and the radiographic variability of MPS VI. The importance of considering MPS in the differential diagnosis of other forms skeletal dysplasia is mandatory. Finally, we stress that the value of early diagnosis is to overcome dreadful complications.

Clinical, Endocrine and Genetic spectrums of Mucopolysaccharidoses type VI in Duhok city, Kurdistan Region, Iraq.

Mucopolysaccharidoses type VI is a rare disorder and establishing the diagnosis requires assays that are unavailable in a routine care setting. There is an increased risk of considerable diagnostic delay and missing patients due to incorrect diagnosis. The present study was conducted to determine the socio-demographic characteristics, clinical manifestations, and anthropometric parameters of patients with MPS type VI. Patients' enzyme levels and genetic profiles were also examined. The present study included a total of 16 patients who had been diagnosed as MPS type VI and were referred to Hivi Pediatric Hospital in Duhok, Kurdistan Region, Iraq, till the time period of March 2022. Diagnoses were made in all the patients by analyzing the enzyme level. Moreover, a genetic study was performed to confirm the diagnosis. From each of the patients, a blood sample was taken to determine the hematological parameters. Among the study participants, 9 were males and 7 were females. The mean age of the patients was 6.81±4.99 years and the age at diagnosis was 21.13±15.19 months. All of them presented with a course facial features, 75% had short stature, 87.5% had corneal clouding, 12.5%  had glaucoma, 68.75% had poor vision, 18.75% of them had optic nerve disease, 56.25% had otitis media, 56.25% had poor hearing, 68.75% had a history of recurrent sinusitis, 50% had an enlarged tongue, and 75% had abnormal teeth. Approximately 56.25% of the patients presented with sleep apnea, 37.5% had obstructive and restrictive airway disease, none of the patients had cardiac arrhythmia, 37.5% had cardiomyopathy, 31.25% had abdominal hepatosplenomegaly, 81.25% had skeletal abnormalities, all of the patients had normal intelligence, 9 (56.25%) had a past medical history of other systemic illness and 7 (43.75%) had a past history of surgery. Out of the total number of patients, 13 patients had c.962T>C (p.(Leu321Pro)) mutation, one patient had c.585T>A (p.(ASP195Glu)) mutation, one patient had c.[585T>A];[753C>G] (Asp195 Glu];[Tyr251 Ter]), and one patient had c.{288C>A];[962T>C]   (p.[Ser96Arg];[Leu321Pro]) mutations. Due to the rarity in prevalence, early detection of the said disorder is critical; early treatment may result in improved outcomes, which may have potential significance for newborn screening.

Increased ocular wall thickness and decreased globe volume in children with mucopolysaccharidosis type VI.

PURPOSE lthough clinical ophthalmologic findings have been reported, no study documented magnetic resonance imaging (MRI) findings in mucopolysaccharidosis (MPS) type VI. The aim of this study was to determine the ophthalmologic imaging findings of MPS type VI in the pediatric age group retrospectively. METHODS Brain MRIs of 10 patients with MPS type VI and 49 healthy children were evaluated independently by two pediatric radiologists for the following characteristics: globe volume, ocular wall thickness, and optic nerve sheath diameter for each orbit. The means of the measurement of each group were compared by using an independent t-test. Agreement and bias between reviewers were assessed by intra-class correlation coefficients (ICC). RESULTS A total of 59 children [32 girls (54.23%), 27 boys (45.77%); age range, 4-16 years; mean age, 10.37 ± 3.73 years] were included in the study. Statistical analysis revealed smaller eyeballs and thicker ocular walls of patients with MPS type VI (P < .001 and P < .001, respectively). However, there was no statistically significant difference in terms of optic nerve sheath diameter between the two groups (P=.648). CONCLUSION Patients with MPS type VI displayed reduced globe volumes and increased ocular wall thicknesses compared to the healthy children. Therefore, we recommend that ophthalmologic imaging findings might prove to be an auxiliary tool in the diagnosis of MPS patients.

Novel chorioretinal findings in two siblings with mucopolysaccharidosis type VI.

PURPOSE: To describe and compare the systemic and ocular findings in two siblings with mucopolysaccharidosis type VI (Maroteaux-Lamy syndrome), one treated with recombinant galsulfase, and one who was untreated. METHOD: One female patient aged 33 years (case 1) who had received galsulfase enzyme replacement therapy for 11 years, and her younger male sibling by 3 years (case 2), who had declined systemic treatment, underwent clinical ophthalmic examination and retinal ocular coherence tomography. The female sibling underwent electrophysiology testing of visual function. RESULTS: Case 1 had best corrected visual acuity right 6/4.8 and left 6/6. Case 2 had best corrected visual acuity of 6/6 in each eye. Case 1 had bilateral mild corneal haze and a clinically unremarkable posterior segment examination. Case 2 had bilateral very mild corneal haze and retinal striae on examination. Ocular coherence tomography showed choroidal folds at the maculae in both patients, more pronounced in Case 2, who also had retinal folds and epiretinal membrane. Electroretinography showed very mild involvement of the rods only in Case 1. CONCLUSION: These two siblings with mucopolysaccharidosis type VI, one treated and one untreated, displayed variable levels of systemic, corneal, and chorioretinal involvement in their disease Further studies of choroidal changes in MPS VI may prove useful as a biomarker of ocular response to treatment outside the blood-retina barrier. Both patients have provided written consent to publish case details.

Compound heterozygous missense mutations in a Chinese mucopolysaccharidosis type VI patient: a case report.

BACKGROUND: Mucopolysaccharidosis type VI (MPS VI) is a rare autosomal recessive inherited disease caused by mutations in the arylsulfatase B (ARSB) gene. MPS VI is a multisystemic disease resulting from a deficiency in arylsulfatase B causing an accumulation of glycosaminoglycans in the tissues and organs of the body. In this report, we present the case of a 16-year-old Chinese male who presented with vision loss caused by corneal opacity. MPS VI was confirmed by genetic diagnosis. CASE PRESENTATION: A 16-year-old Chinese male presented with a one-year history of binocular vision loss. The best-corrected visual acuity was 0.25 in the right eye and 0.5 in the left eye. Although slit-lamp examination revealed corneal opacification in both eyes, the ocular examinations of his parents were normal. At the same time, the patient presented with kyphotic deformity, short stature, joint and skeletal malformation, thick lips, long fingers, and coarse facial features. Genetic assessments revealed that ARSB was the causative gene. Compound heterozygous missense mutations were found in the ARSB gene, namely c.1325G > A (p. Thr442Met) (M1) and c.1197G > C (p. Phe399Leu) (M2). Genetic diagnosis confirmed that the patient had MPS VI. CONCLUSIONS: This paper reports a case of MPS VI confirmed by genetic diagnosis. MPS VI is a multisystem metabolic disease, with corneal opacity as a concomitant ocular symptom. As it is difficult for ophthalmologists to definitively diagnose MPS VI, genetic testing is useful for disease confirmation.

Otorhinolaryngological manifestations in 61 patients with mucopolysaccharidosis.

OBJECTIVES: The mucopolysaccharidoses (MPS) are inherited lysosomal storage disorders with multisystemic and highly variable clinical manifestation. ENT symptoms are common and early signs of MPS. The most common ENT diagnoses are chronic/recurrent rhinosinusitis, acute otitis media, otitis media with effusion, hearing loss and airway obstruction. METHODS: A single-centre retrospective chart review of 61 patients (36 M/25F) with different MPS subtypes (MPS I (n = 15), MPS II (n = 10), MPS III (n = 17), MPS IV (n = 15) and MPS VI (n = 4)) was conducted. The age of ENT presentation and frequency of ENT symptoms, surgeries and their distribution among MPS subtypes was studied. The relationship between ENT presentation, first ENT surgery and the age of diagnosis was also evaluated. RESULTS: Median age at the first ENT manifestation was 2.8 years, median age at MPS diagnosis 4.1 years. The great majority of patients (90%) manifested at least one ENT diagnosis; often before the diagnosis of MPS (75%). Chronic/recurrent rhinosinusitis was the most prevalent ENT diagnosis (77%), followed by upper airway obstruction (65%) and hearing loss (53%). Chronic/recurrent rhinosinusitis was the first ENT symptom to appear (median age 2.2 years), followed by otitis media with effusion (3.7 years) and hearing loss (4.5 years). At least one ENT surgery was performed in 57% of patients; in 69% before MPS diagnosis was established. Median age of the first ENT surgery was 4.1 years. ENT symptoms and surgical procedures were earliest present in MPS II. CONCLUSIONS: Our study documents high and early occurrence of various otolaryngologic symptoms in MPS and thus highlights the role of ENT specialist in prompt diagnosis of these rare diseases and their long-term management.

Recommendations for the management of MPS VI: systematic evidence- and consensus-based guidance.

INTRODUCTION: Mucopolysaccharidosis (MPS) VI or Maroteaux-Lamy syndrome (253200) is an autosomal recessive lysosomal storage disorder caused by deficiency in N-acetylgalactosamine-4-sulfatase (arylsulfatase B). The heterogeneity and progressive nature of MPS VI necessitates a multidisciplinary team approach and there is a need for robust guidance to achieve optimal management. This programme was convened to develop evidence-based, expert-agreed recommendations for the general principles of management, routine monitoring requirements and the use of medical and surgical interventions in patients with MPS VI. METHODS: 26 international healthcare professionals from various disciplines, all with expertise in managing MPS VI, and three patient advocates formed the Steering Committee group (SC) and contributed to the development of this guidance. Members from six Patient Advocacy Groups (PAGs) acted as advisors and attended interviews to ensure representation of the patient perspective. A modified-Delphi methodology was used to demonstrate consensus among a wider group of healthcare professionals with expertise and experience managing patients with MPS VI and the manuscript has been evaluated against the validated Appraisal of Guidelines for Research and Evaluation (AGREE II) instrument by three independent reviewers. RESULTS: A total of 93 guidance statements were developed covering five domains: (1) general management principles; (2) recommended routine monitoring and assessments; (3) enzyme replacement therapy (ERT) and hematopoietic stem cell transplantation (HSCT); (4) interventions to support respiratory and sleep disorders; (5) anaesthetics and surgical interventions. Consensus was reached on all statements after two rounds of voting. The greatest challenges faced by patients as relayed by consultation with PAGs were deficits in endurance, dexterity, hearing, vision and respiratory function. The overall guideline AGREE II assessment score obtained for the development of the guidance was 5.3/7 (where 1 represents the lowest quality and 7 represents the highest quality of guidance). CONCLUSION: This manuscript provides evidence- and consensus-based recommendations for the management of patients with MPS VI and is for use by healthcare professionals that manage the holistic care of patients with the intention to improve clinical- and patient-reported outcomes and enhance patient quality of life. It is recognised that the guidance provided represents a point in time and further research is required to address current knowledge and evidence gaps.

Maroteaux-Lamy syndrome: a rare and challenging case of mitral valve replacement.

Maroteaux-Lamy syndrome is a very rare multisystem disorder. Cardiac valve surgery is common in these patients who present a unique set of perioperative and intraoperative challenges to the surgeon and treating team. We describe successful mitral valve replacement using an inverted aortic prosthesis in a 29-year-old lady with Maroteaux-Lamy syndrome, with a good result at 10 months.

Mucopolysaccharidosis type VI (MPS VI) and molecular analysis: Review and classification of published variants in the ARSB gene.

Maroteaux-Lamy syndrome (MPS VI) is an autosomal recessive lysosomal storage disorder caused by pathogenic ARSB gene variants, commonly diagnosed through clinical findings and deficiency of the arylsulfatase B (ASB) enzyme. Detection of ARSB pathogenic variants can independently confirm diagnosis and render genetic counseling possible. In this review, we collect and summarize 908 alleles (201 distinct variants, including 3 polymorphisms previously considered as disease-causing variants) from 478 individuals diagnosed with MPS VI, identified from literature and public databases. Each variant is further analyzed for clinical classification according to American College of Medical Genetics and Genomics (ACMG) guidelines. Results highlight the heterogeneity of ARSB alleles, with most unique variants (59.5%) identified as missense and 31.7% of unique alleles appearing once. Only 18% of distinct variants were previously recorded in public databases with supporting evidence and clinical significance. ACMG recommends publishing clinical and biochemical data that accurately characterize pathogenicity of new variants in association with reporting specific alleles. Variants analyzed were sent to ClinVar (https://www.ncbi.nlm.nih.gov/clinvar/), and MPS VI locus-specific database (http://mps6-database.org) where they will be available. High clinical suspicion coupled with diagnostic testing for deficient ASB activity and timely submission and classification of ARSB variants with biochemical and clinical data in public databases is essential for timely diagnosis of MPS VI.

A long term follow-up study of the development of hip disease in Mucopolysaccharidosis type VI.

Hip problems in Mucopolysaccharidosis type VI (MPS VI) lead to severe disability. Lack of data on the course of hip disease in MPS VI make decisions regarding necessity, timing and type of surgical intervention difficult. We therefore studied the development of hip pathology in MPS VI patients over time. Data were collected as part of a prospective follow-up study. Standardized supine AP pelvis and frog leg lateral radiographs of both hips were performed yearly or every 2years. Image assessment was performed quantitatively (angle measurements) and qualitatively (hip morphology). Clinical burden of hip disease was evaluated by physical examination, six minute walking test (6MWT) and a questionnaire assessing pain, wheelchair-dependency and walking distance. A total of 157 pelvic radiographs of 14 ERT treated MPS VI patients were evaluated. Age at first image ranged from 2.0 to 21.1years. Median follow up duration was 6.8years. In all patients, even in the youngest, the acetabulum and os ilium were dysplastic. Coverage of the femoral head by the acetabulum improved over time, but remained insufficient. While the femoral head appeared normal in the radiographs at young age, the ossification pattern became abnormal in all patients over time. In all patients the distance covered in the 6MWT was reduced (median Z scores -3.3). Twelve patients had a waddling gait. Four patients were partially wheelchair-dependent and ten patients had limitations in their maximum walking distance. In conclusion, clinically significant hip abnormalities develop in all MPS VI patients from very early in life, starting with deformities of the os ilium and acetabulum. Femoral head abnormalities occur later, most likely due to altered mechanical forces in combination with epiphyseal abnormalities due to glycosaminoglycan storage. The final shape and angle of the femoral head differs significantly between individual MPS VI patients and is difficult to predict.

Mucopolysaccharidosis VI: pathophysiology, diagnosis and treatment.

Mucopolysaccharidosis VI (MPS VI), or Maroteaux-Lamy syndrome, is an autosomal recessive lysosomal storage disorder caused by deficient activity of the enzyme arylsulfatase B (ASB). Progressive accumulation of glycosaminoglycans (GAGs) in organs and tissues leads to the development of multisystem clinical manifestations. The presentation of MPS VI is genotypically and phenotypically diverse, with a large number of potential disease-causing mutations and a phenotypic spectrum ranging from very slowly to very rapidly progressing disease. Diagnosis of MPS VI relies on presence of clinical features, increased GAG levels in urine or low ASB activity in dried blood spots, and measurement of enzyme activity levels in leukocytes or fibroblasts. The management of MPS VI involves enzyme replacement therapy and medical and surgical treatment of disease manifestations. Liquid chromatography/tandem mass spectrometry of GAG-derived disaccharides in blood or urine is emerging as a valuable method in the diagnosis, prognosis and assessment of therapeutic efficacy in MPS VI.

IgE-Mediated Hypersensitivity and Desensitisation with Recombinant Enzymes in Pompe Disease and Type I and Type VI Mucopolysaccharidosis.

Enzyme replacement therapy (ERT) is important for the treatment of lysosomal storage disorders. Hypersensitivity reactions with ERT have been reported, and in these cases, desensitisation with the enzyme is necessary. Here we report the cases of 3 patients with lysosomal storage disorders, including Pompe disease and mucopolysaccharidosis type I and VI, who had IgE-mediated hypersensitivity reactions and positive skin tests. Successful desensitisation protocols with the culprit enzyme solution were used for these patients. All 3 patients were able to safely receive ERT with the desensitisation protocol.

Eficacia y seguridad de galsulfasa en pacientes con diagnóstico de mucopolisacaridosis tipo VI / Efficacy and safety of galsulfase in patients with a diagnosis of mucopolysaccharidosis type VI

INTRODUCCION: Antecedentes: El Instituto de Evaluación de Tecnologías en Salud e Investigación (IETSI) ha recibido la solicitud de evaluar el uso de Galsulfasa para el uso en pacientes con diagnóstico de mucopolisacaridosis tipo VI (MPS-VI) confirmada por pruebas enzimáticas o genéticas y que presentan síntomas y signos propios de la enfermedad, indicación actualmente no contemplada en el Petitorio Farmacológico de ESSALUD. Aspectos Generales: La mucopolisacaridosis de tipo VI (MPS-VI) o síndrome de Maroteaux-Lamy es una enfermedad de almacenamiento lisosómico con afectación sistémica progresiva, asociada a un déficit de la enzima N-acetilgalactosamina 4-sulfatasa, conocida también como arilsulfatasa B (ASB). Este déficit enzimático provoca la acumulación de dermatán sulfato. Esta enfermedad presenta un amplio espectro de signos y síntomas. Se caracteriza por presentar displasia esquelética que incluye: estatura baja, disostosis múltiple y enfermedad articular degenerativa. La MPS-VI es una enfermedad de transmisión autosómica recesiva, causada por mutaciones en el gen ARSB, ubicado en el cromosoma 5. Se estima que aproximadamente 1 en 340,000 nacimientos están afectados con MPS-VI. Tecnología Sanitaria de Interés: Galsulfasa: La galsulfasa (Naglazyme O) es una forma recombinante de la enzima N-acetilgalactosamina-4-sulfatasa humana. Es el único tratamiento de reemplazo enzimático propuesto disponible para la MPS-VI. El fundamento y mecanismo de acción del tratamiento enzimático sustitutivo es restablecer un nivel de actividad enzimática suficiente para hidrolizar el sustrato y evitar la acumulación de dermatán sulfato. Tras la perfusión intravenosa, la galsulfasa se elimina rápidamente de la circulación y es captada por las células, probablemente por los receptores manosa-6-fosfato, y transportada a los lisosomas.\r\nMETODOLOGÍA: Se realizó una búsqueda de la literatura con respecto a la eficacia y seguridad de \r\nGalsulfasa para el tratamiento de MPS-VI en las bases de datos de MEDLINE, EMBASE, CENTRAL, DARE y TRIPDATABASE. Se hizo una búsqueda adicional en www.clinicaltrials.gov, para poder identificar ensayos clínicos aún en elaboración o que no hayan sido publicados. RESULTADOS: Sinopsis de la Evidencia: Se realizó la búsqueda bibliográfica y de evidencia científica que sustente el uso de galsulfasa en el tratamiento de MPS-VI. Guías Clínicas: se identificaron cuatro documentos de guías de tratamiento; Evaluaciones de tecnología sanitaria: se identificó una ETS (España). Galsulfasa no ha sido evaluado hasta el momento por las agencias de ETS de NICE o IETS, tampoco por ningunas de las agencias miembros de la INAHTA; Revisiones sistemáticas: Se identificó una RS Cochrane; Ensayos clínicos: se identificaron cuatro ensayos de los cuales solo uno es un ECA fase III controlado con placebo, el resto corresponden a ensayos de un solo brazo sin grupo comparador (un ensayo fase 1/11, uno de fase II, uno de fase IV); Ensayos Clínicos registrados: se encontró un estudio registrado en fase de reclutamiento; Estudios observacionales: se identificó un estudio transversal con mediciones en dos puntos temporales. CONCLUSIONES: La presente evaluación identificó cinco ensayos que evaluaron galsulfasa en la MPS VI y un reciente estudio transversal. El estudio de Harmatz 2006 es el único ensayo que provee información sobre la eficacia de galsulfasa por ser aleatorizado y controlado con placebo. El resto de ensayos fueron de fase I o II de un solo brazo o comparando dos dosis diferentes, y en muestras pequeñas (5 10 pacientes). El estudio transversal comparó parámetros clínicos y de laboratorio de pacientes con MPS VI obtenidos en dos encuestas realizadas con diez años de diferencia, pero en la segunda medición solo se recogió información de aproximadamente la mitad de los pacientes. El Instituto de Evaluación de Tecnología en Salud e Investigación-IETSI, no aprueba el uso de galsulfasa para el tratamiento de la mucopolisacaridosis tipo VI.

Short Communication Impact of early enzyme-replacement therapy for mucopolysaccharidosis VI: results of a long-term follow-up of Brazilian siblings.

Mucopolysaccharidosis type VI (MPS VI) is an autosomal recessive multisystem lysosomal storage disorder, which is characterized by the deficiency of the enzyme arylsulfatase B encoded by the ARSB gene. Treatment of this disease with enzyme-replacement therapy (ERT) improves the clinical status of and generates hope for MPS VI patients. However, only few reports on patients with MPS VI treated before 5 years of age have been published. Thus, the objective of this study was to compare the clinical parameters of two sisters affected by MPS VI who started ERT at different ages (9 years and 1 year 5 months, respectively) and to determine the most relevant clinical impacts of early treatment after 85 months of evaluation. The treatment was well tolerated by both siblings. ERT in the younger sibling resulted in increased growth, an improved 6-minute walk test, less coarse face, slower progression of cardiac valve disease, and the absence of compressive myelopathy compared to that in her older sister. On the other hand, the older sibling had typical MPS VI phenotypic features before the commencement of ERT. Corneal clouding, clawed hands, and progressive skeletal changes were observed in both siblings despite the treatment. Both siblings displayed reduced frequencies of upper respiratory infections and apnea indices. This study emphasizes that early diagnosis and treatment of MPS VI are critical for a better disease outcome and to enhance the quality of life for these patients.

[Management of mucopolysaccharidosis type VI in adults]. / SMJERNICE ZA LIJECENJE MUKOPOLISAHARIDOZE (MPS) VI U ODRASLIH BOLESNIKA.

Mucopolysaccharidosis type VI (Maroteaux-Lamy syndrome, MPS VI) is a progressive multisystemic lysosomal storage disease. Physical symptoms generally include growth retardation, and bone dysplasia. Enzyme replacement therapy is the treatment of choice and is done with recombinant version of enzyme N-acetylgalactosamine 4-sulfatase (galsulfase) which is administered intravenously. The enzyme replacement therapy should be applied once a week as a life-long treatment. Division of metabolic diseases, Department of internal medicine, University Hospital Center Zagreb continues with the treatment of MPS VI patients after they turn 18 years of life and are not treated any more by the pediatricians. The aim of this document is to provide the guidelines for diagnosis and management of adult patients with MPS VI which consists not only of regular galsulfase adiministration, but also of regular follow up and treatment of numerous comorbidities. These guidelines were produced by experts from the Division of metabolic diseases, Department of internal medicine, University Hospital Center Zagreb which is the Referral center for rare and metabolic diseases of the Ministry of Health, Republic of Croatia. The guidelines are result of collaboration with pediatricians, radiologists and biochemists without whose experience and advices appropriate treatment of these patients would not be possible. The guidelines were endorsed by the Croatian society for rare diseases, Croatian Medical Association.

Identifying the need for a multidisciplinary approach for early recognition of mucopolysaccharidosis VI (MPS VI).

Mucopolysaccharidosis VI (MPS VI, Maroteaux-Lamy syndrome) is caused by deficient activity of the enzyme, N-acetylgalactosamine-4-sulfatase, resulting in impaired degradation of the glycosaminoglycan dermatan sulfate. Patients experience a range of manifestations including joint contractures, short stature, dysostosis multiplex, coarse facial features, decreased pulmonary function, cardiac abnormalities, corneal clouding and shortened life span. Recently, clinicians from institutions in the Asia-Pacific region met to discuss the occurrence and implications of delayed diagnosis and misdiagnosis of MPS VI in the patients they have managed. Eighteen patients (44% female) were diagnosed. The most common sign presented by the patients was bone deformities in 11 patients (65%). Delays to diagnosis occurred due to the lack of or distance to diagnostic facilities for four patients (31%), alternative diagnoses for two patients (15%), and misleading symptoms experienced by two patients (15%). Several patients experienced manifestations that were subtler than would be expected and were subsequently overlooked. Several cases highlighted the unique challenges associated with diagnosing MPS VI from the perspective of different specialties and provide insights into how these patients initially present, which may help to elucidate strategies to improve the diagnosis of MPS VI.

Improving arylsulfatase activity determination in dried blood spots: Screening and diagnostic approaches for Maroteaux-Lamy syndrome (MPS VI).

BACKGROUND: Mucopolysaccharidosis type VI can be screened by measuring the lysosomal arylsulfatase B (ARSB) residual enzyme activity in dried blood spots (DBS) using synthetic substrates. However, we have found experimental obstacles when determining ARSB activity with the fluorescent method due to the significant quenching effect rendered by DBS components. METHODS: We adapted the methods originally described by Chamoles et al. [1] and Civallero et al. [2] and put forward 2 distinct approaches for ARSB activity quantification from DBS samples by measuring the 4-methylumbelliferone (ß-MU) fluorescence generated from the ARSB 4-methylumbelliferone sulfate (ß-MUS) substrate. RESULTS: We demonstrate the high throughput feasibility of a novel approach for measuring ARSB activities by incorporating tailor-made calibration curves according to each patient's DBS sample quenching properties. The second method is used to calculate ARSB activities by measuring the fluorescence and absorbance parameters in each reaction sample with a single DBS-free calibration curve. CONCLUSIONS: The quantitative correlation between the DBS sample absorbance and its quenching effect can be used to calculate predictive ARSB activities and would serve as an affordable first tier screening test. The method described herein demonstrates the critical importance of adapting the ß-MU calibration curves to each patient's unique DBS sample matrix and its positive impact on the accuracy and reliability of ARSB activity measurements.

Mucopolysaccharidosis type VI in a juvenile miniature schnauzer dog with concurrent hypertriglyceridemia, necrotizing pancreatitis, and diabetic ketoacidosis.

A 7-month-old, neutered male miniature schnauzer dog with a history of cryptorchidism and umbilical hernia was referred for diabetic ketoacidosis. Clinical evaluation revealed stunted growth, skeletal abnormalities, hypertriglyceridemia, diabetic ketoacidosis, and acute necrotizing pancreatitis. Further testing was diagnostic for mucopolysaccharidosis type VI causing the stunted growth and skeletal deformities, but no connection between mucopolysaccharidosis type VI, hypertriglyceridemia, and pancreatic diseases was found.

Mucopolysaccharidose de type VI chez un jeune chien Schnauzer miniature atteint d'hypertriglycéridémie, de pancréatite nécrosante et d'acidocétose diabétique concomitantes. Un chien Schnauzer miniature castré âgé de 7 mois avec une anamnèse de cryptorchidie et d'hernie ombilicale a été référé pour une acidocétose diabétique. L'évaluation clinique a révélé une croissance arrêtée, des anomalies squelettiques, l'hypertriglycéridemie, l'acidocétose diabétique et une pancréatite nécrosante aiguë. Des tests supplémentaires ont permis de diagnostiquer une mucopolysaccharidose de type VI causant une croissance arrêtée et des difformités squelettiques, mais aucun lien avec la mucopolysaccharidose de type VI, l'hypertriglycéridémie et les maladies pancréatiques n'a été trouvé.(Traduit par Isabelle Vallières).