Identification of Orthosteric and Allosteric Pharmacological Chaperones for Mucopolysaccharidosis Type IIIB.

Mucopolysaccharidosis type IIIB (MPS IIIB) is an autosomal inherited disease caused by mutations in gene encoding the lysosomal enzyme N-acetyl-alpha-glucosaminidase (NAGLU). These mutations result in reduced NAGLU activity, preventing it from catalyzing the hydrolysis of the glycosaminoglycan heparan sulfate (HS). There are currently no approved treatments for MPS IIIB. A novel approach in the treatment of lysosomal storage diseases is the use of pharmacological chaperones (PC). In this study, we used a drug repurposing approach to identify and characterize novel potential PCs for NAGLU enzyme. We modeled the interaction of natural and artificial substrates within the active cavity of NAGLU (orthosteric site) and predicted potential allosteric sites. We performed a virtual screening for both the orthosteric and the predicted allosteric site against a curated database of human tested molecules. Considering the binding affinity and predicted blood-brain barrier permeability and gastrointestinal absorption, we selected atovaquone and piperaquine as orthosteric and allosteric PCs. The PCs were evaluated by their capacity to bind NAGLU and the ability to restore the enzymatic activity in human MPS IIIB fibroblasts These results represent novel PCs described for MPS IIIB and demonstrate the potential to develop novel therapeutic alternatives for this and other protein deficiency diseases.

[Natural history of mucopolysaccharidosis type III in a series of Colombian patients]. / Historia natural de la mucopolisacaridosis III en una serie de pacientes colombianos.

INTRODUCTION: Mucopolysaccharidosis type III (MPS III), also known as Sanfilippo syndrome, is a lysosomal storage disease with progressive neurodegenerative features, predominantly affecting the central nervous system. Diagnosis is based on clinical features, with neurodevelopmental and neuropsychiatric alterations taking precedence, including over phenotype alterations. The disease is confirmed by biochemical analysis to identify the type of glycosaminoglycans present, enzyme assay and molecular genetic studies. CASE REPORTS: A clinical description was performed for eight patients diagnosed with MPS III in Colombia. Their initial symptoms were related to developmental delay and behavioural disorders presenting between 3 and 8 years of age, associated in all cases with coarse facial features, thick eyebrows, hepatomegaly and progressive hearing loss. One of the patients presented cardiac anomalies; two presented focal epilepsy; and one presented optic atrophy. They all presented neuroimaging alterations, with evidence of parenchymal volume loss, corpus callosum atrophy and cortical thinning; the diagnosis was performed by biochemical glycosaminoglycan chromatography studies, and all patients have a confirmatory genetic study. CONCLUSIONS: MPS III is a challenge for diagnosis, particularly in its early stages and in patients in which the course of the disease is attenuated. This is due to its variable course, non-specific early neuropsychiatric symptoms, and the absence of obvious somatic features compared to other types of MPS. After a definitive diagnosis has been made, interdisciplinary care must be provided for the patient and their family, and support given for the treatment of physical symptoms, ensuring the best possible care and quality of life for the patient and their family, as the condition is neurodegenerative.

TITLE: Historia natural de la mucopolisacaridosis III en una serie de pacientes colombianos.Introducción. La mucopolisacaridosis de tipo III (MPS III), o síndrome de Sanfilippo, es un trastorno de almacenamiento lisosómico con características neurodegenerativas progresivas, predominante del sistema nervioso central. Su diagnóstico se basa en el cuadro clínico, y priman alteraciones en el neurodesarrollo y neuropsiquiátricas, incluso antes de la presencia de alteraciones fenotípicas. El análisis bioquímico para identificar el tipo de glucosaminoglucanos presente, la determinación enzimática y el estudio de genética molecular confirman la enfermedad. Casos clínicos. Se realiza la descripción clínica de ocho pacientes con diagnóstico de MPS III en Colombia, con síntomas iniciales en relación con retraso del desarrollo y trastornos comportamentales evidenciados entre los 3 y 8 años, asociado a facies toscas, cejas pobladas, hepatomegalia y pérdida auditiva progresiva en todos los casos. Uno de los pacientes presentó anomalías cardíacas; dos de ellos, epilepsia focal; y en uno se evidenció atrofia óptica. Todos presentaron alteraciones en las neuroimágenes con evidencia de pérdida del volumen parenquimatoso, atrofia del cuerpo calloso y adelgazamiento cortical; el diagnostico se realizó a través de estudios bioquímicos de cromatografía de glucosaminoglucanos y todos cuentan con un estudio genético confirmatorio. Conclusiones. La MPS III es un desafío diagnóstico, particularmente en pacientes con un curso atenuado de la enfermedad, debido al curso variable, síntomas neuropsiquiátricos tempranos inespecíficos y falta de características somáticas evidentes en comparación con otros tipos de MPS. Cuando se tiene el diagnóstico definitivo, es fundamental brindar atención interdisciplinaria para el paciente y la familia, y apoyar el tratamiento de los síntomas físicos, garantizando ofrecer el mejor cuidado posible y la mejor calidad de vida para el paciente y su familia, al tratarse de una condición neurodegenerativa.

Evidence of epigenetic landscape shifts in mucopolysaccharidosis IIIB and IVA.

Lysosomal storage diseases (LSDs) are a group of monogenic diseases characterized by mutations in genes coding for proteins associated with the lysosomal function. Despite the monogenic nature, LSDs patients exhibit variable and heterogeneous clinical manifestations, prompting investigations into epigenetic factors underlying this phenotypic diversity. In this study, we focused on the potential role of epigenetic mechanisms in the pathogenesis of mucopolysaccharidosis IIIB (MPS IIIB) and mucopolysaccharidosis IVA (MPS IVA). We analyzed DNA methylation (5mC) and histone modifications (H3K14 acetylation and H3K9 trimethylation) in MPS IIIB and MPS IVA patients' fibroblasts and healthy controls. The findings revealed that global DNA hypomethylation is present in cell lines for both diseases. At the same time, histone acetylation was increased in MPS IIIB and MPS IVA cells in a donor-dependent way, further indicating a shift towards relaxed open chromatin in these MPS. Finally, the constitutive heterochromatin marker, histone H3K9 trimethylation, only showed reduced clustering in MPS IIIB cells, suggesting limited alterations in heterochromatin organization. These findings collectively emphasize the significance of epigenetic mechanisms in modulating the phenotypic variations observed in LSDs. While global DNA hypomethylation could contribute to the MPS pathogenesis, the study also highlights individual-specific epigenetic responses that might contribute to phenotypic heterogeneity. Further research into the specific genes and pathways affected by these epigenetic changes could provide insights into potential therapeutic interventions for these MPS and other LSDs.

Longitudinal Natural History of Pediatric Subjects Affected with Mucopolysaccharidosis IIIB.

OBJECTIVE: To characterize the longitudinal natural history of disease progression in pediatric subjects affected with mucopolysaccharidosis (MPS) IIIB. STUDY DESIGN: Sixty-five children with a confirmed diagnosis of MPS IIIB were enrolled into 1 of 2 natural history studies and followed for up to 4 years. Cognitive and adaptive behavior functions were analyzed in all subjects, and volumetric magnetic resonance imaging analysis of liver, spleen, and brain, as well as levels of heparan sulfate (HS) and heparan sulfate nonreducing ends (HS-NRE), were measured in a subset of subjects. RESULTS: The majority of subjects with MPS IIIB achieved an apex on both cognition and adaptive behavior age equivalent scales between age 3 and 6 years. Development quotients for both cognition and adaptive behavior follow a linear trajectory by which subjects reach a nadir with a score <25 for an age equivalent of 24 months by age 8 years on average and by 13.5 years at the latest. All tested subjects (n = 22) had HS and HS-NRE levels above the normal range in cerebrospinal fluid and plasma, along with signs of hepatomegaly. Subjects lost an average of 26 mL of brain volume (-2.7%) over 48 weeks, owing entirely to a loss of cortical gray matter (32 mL; -6.5%). CONCLUSIONS: MPS IIIB exists along a continuum based on cognitive decline and cortical gray matter atrophy. Although a few individuals with MPS IIIB have an attenuated phenotype, the majority follow predicted trajectories for both cognition and adaptive behavior. TRIAL REGISTRATION: ClinicalTrials.gov identifiers NCT02493998, NCT03227042, and NCT02754076.

Sanfilippo syndrome type B: Analysis of patients diagnosed by the MPS Brazil Network.

Mucopolysaccharidosis type IIIB is a rare autosomal recessive disorder characterized by deficiency of the enzyme N-acetyl-alpha-d-glucosaminidase (NAGLU), caused by biallelic pathogenic variants in the NAGLU gene, which leads to storage of heparan sulfate and a series of clinical consequences which hallmark is neurodegeneration. In this study clinical, epidemiological, and biochemical data were obtained from MPS IIIB patients diagnosed from 2004-2019 by the MPS Brazil Network ("Rede MPS Brasil"), which was created with the goal to provide an easily accessible and comprehensive investigation of all MPS types. One hundred and ten MPS IIIB patients were diagnosed during this period. Mean age at diagnosis was 10.9 years. Patients were from all over Brazil, with a few from abroad, with a possible cluster of MPS IIIB identified in Ecuador. All patients had increased urinary levels of glycosaminoglycans and low NAGLU activity in blood. Main clinical symptoms reported at diagnosis were coarse facies and neurocognitive regression. The most common variant was p.Leu496Pro (30% of alleles). MPS IIIB seems to be relatively frequent in Brazil, but patients are diagnosed later than in other countries, and reasons for that probably include the limited awareness about the disease by health professionals and the difficulties to access diagnostic tests, factors that the MPS Brazil Network is trying to mitigate.

Mutación novel en el Síndrome Sanfilippo B. Presentación de un caso / A novel mutation in Sanfilippo Syndrome type B. Case report

Introducción: El Síndrome Sanfilippo B es un error innato en el metabolismo lisosomal, con herencia autosómica recesiva. Se caracteriza por facie ligeramente tosca, deterioro neurológico progresivo y poca repercusión somática, provocado por mutaciones en el gen NAGLU, cuyo locus es 17q21.2. La incidencia internacionalmente es muy baja y en Cuba solo se han diagnosticado siete pacientes desde 1985. Objetivo: Describir las manifestaciones clínicas, bioquímicas y moleculares de un paciente cubano diagnosticado con Síndrome Sanfilippo B. Presentación de Caso: Se describió un paciente de 13 años, cuyas principales manifestaciones clínicas fueron: facie ligeramente tosca, sinofris, alteraciones de conducta y deterioro neurológico progresivo. El trastorno del sueño fue ocasional y frecuente las infecciones respiratorias. Se demostró la presencia de colitis ulcerativa y pólipo intestinal. Se confirmó excreción aumentada de heparán sulfato y disminución de la actividad enzimática N-acetil αD-glucosaminidasa. Se identificó la mutación c.640dupC en el gen NAGLU en homocigosis en el paciente y ambos padres resultaron ser portadores. Conclusiones: Predominaron las alteraciones de conducta, deterioro neurológico progresivo e infecciones respiratorias en el caso reportado; siendo la colitis ulcerativa y el pólipo intestinal un hallazgo no descrito anteriormente para esta enfermedad. Los estudios cromatográficos y enzimáticos resultaron positivos para Sanfilippo B. El genotipo de este paciente resultó ser homocigótico para una nueva variante alélica patogénica en el gen NAGLU. Se demostró la segregación mendeliana de la mutación en la familia(AU)

Introduction: Sanfilippo syndrome type B is an autosomal recessive lysosomal storage disease. The frequent clinical manifestations include slightly coarse facial features, progressive neurodegeneration and mild somatic repercussion caused by mutations in the NAGLU gene, whose locus is 17q21.2. The worldwide incidence is very low and only seven patients have been diagnosed in Cuba since 1985. Objective: To describe clinical, biochemical and molecular characteristics of a Cuban patient with the diagnosis of Sanfilippo Syndrome type B. Case presentation: A 13 years old patient was described. The main clinical manifestations included mild coarse facie, synophrys, behavior disturbances, and progressive neurologic deterioration. Intermittent sleep disturbance and frequent upper respiratory infections were identified. Ulcerative colitis and intestinal polyp were demonstrated. Increased excretion of heparan sulfate and very low N-acetyl α-Dglucosaminidase activity were confirmed. In addition, the presence of mutation c.640dupC in NAGLU gene was identified. The patient had homozygous genotype and both parents were heterozygous. Conclusions: Behavioral alterations, progressive neurological deterioration and respiratory infections predominated in the reported case. Other findings such as ulcerative colitis and intestinal polyps were not previously described in this disease. The chromatographic and enzymatic studies were positive for Sanfilippo type B. This patient's genotype was found to be homozygous for a novel pathogenic allelic variant in the NAGLU gene. Mendelian segregation of the mutation in the family was demonstrated(AU)

Manifestaciones bucales de pacientes con mucopolisacaridosis / Oral manifestations in patients with mucopolysaccharidosis

Objetivo: Describir las características bucales prevalentes de pacientes argentinos con mucopolisacaridosis (MPS) atendidos en el Servicio de Odontología del Hospital Nacional "Prof. Alejandro Posadas". Materiales y métodos: Se consideraron las historias clínicas de 19 pacientes con diagnóstico de MPS. Se registraron la edad, el sexo, el lugar de residencia, el tipo de MPS y la presencia de retraso madurativo. La muestra estuvo constituida por 13 niños (6,7±3 años) y 6 adultos (26±9 años): 2 eran mujeres (1 con MPS tipo I; 1 con MPS tipo IV A) y 17 eran hombres (15 con MPS tipo 2; 1 con MPS tipo 1; 1 con MPS tipo III); 13 de los pacientes presentaban discapacidad intelectual. Se evaluaron: tipo de dentición, oclusión, macroglosia, hipoplasias del esmalte, tipo de respiración predominante, clase molar y tratamiento realizado. Resultados: Ambos casos con MPS I presentaban mordida abierta anterior y giroversión dental, y solo uno de estos, diastemas, microdoncia, hipoplasias del esmalte, macroglosia y respiración bucal. De los 15 pacientes con MPS II, 11 presentaban mordida abierta anterior (73%), 3 mordida cruzada posterior (20%), 5 giroversión dental (33%), 11 diastemas (73%), 3 retraso en la erupción (20%), 4 hiperplasia gingival (26%), 13 macroglosia (87%), 7 hipoplasias del esmalte (47%), 2 microdoncia (13%), 9 respiración bucal (60%). Se registraron 5 pacientes con clase molar I (33%), 3 con clase molar II (20%), 3 con clase molar III (20%) y en 3 casos no se pudo evaluar (20%). En el paciente con MPS tipo III se halló mordida abierta anterior, diastemas, retraso en la erupción, macroglosia, respiración bucal y clase molar II; y en el caso de MPS tipo IV A, mordida abierta anterior, diastemas, hiperplasia gingival, macroglosia y clase molar II. El 90% de los pacientes requirió tratamiento odontológico (AU)

Aim: To identify the most prevalent oral manifestations of 19 Argentine patients with mucopolysaccharidos (MPS) attending the Dentistry Service of the National Posadas Hospital. Materials and methods: The medical records of 19 patients diagnosed with MPS were considered. Age, sex, place of residence, type of MPS, and presence of maturational delay were recorded. The sample consisted of 13 children (6.7 ± 3 years) and 6 adults (26 ± 9 years): 2 were women (1 with MPS type I; 1 with MPS type IV A) and 17 were men (15 with MPS type 2; 1 with MPS type 1; 1 with MPS type III); 13 of the patients had intellectual disabilities. The following were evaluated: type of dentition, occlusion, macroglossia, enamel hypoplasia, predominant type of respiration, molar class and treatment performed Results: Both cases with MPS I presented anterior open bite and dental gyroversion, and only one of these, diastemas, microdontia, enamel hypoplasia, macroglossia and mouth respiration. Of the 15 patients with MPS II, 11 presented anterior open bite (73%), 3 posterior crossbite (20%), 5 dental gyroversion (33%), 11 diastemas (73%), 3 delayed eruption (20%), 4 gingival hyperplasia (26%), 13 macroglossia (87%), 7 enamel hypoplasia (47%), 2 microdontia (13%), 9 mouth breathing (60%). 5 patients with molar class I (33%), 3 with molar class II (20%), 3 with molar class III (20%) and in 3 cases it could not be evaluated (20%). In the patient with type III MPS, anterior open bite, diastemas, delayed eruption, macroglossia, mouth breathing and molar class II were found; and in the case of type IV A MPS, anterior open bite, diastemas, gingival hyperplasia, macroglossia and molar class II. 90% of the patients required dental treatment. Conclusion: The most observed oral manifestations were macroglossia (84.2%) and anterior open bite (73%) (AU)

Linfangiectasia intestinal en un paciente afectado de síndrome de Sanfilippo B / Intestinal lymphangiectasia in a patient with Sanfilippo B syndrome

La mucopolisacaridosis tipo III B es una enfermedad de depósito lisosomal causada por la deficiencia de la enzima N-acetil-alfa-d-glucosaminidasa, implicada en el catabolismo del heparán sulfato, que produce su acúmulo en diversos tejidos. Se presenta a un paciente de 8 años, afectado de mucopolisacaridosis tipo III B, con historia de diarrea crónica y hallazgos endoscópicos e histológicos compatibles con linfangiectasia intestinal. Tras tratamiento dietético con restricción de ácidos grasos de cadena larga y rica en triglicéridos de cadena media, presentó mejoría clínica, mantenida hasta la actualidad.La patogenia de la diarrea crónica en pacientes con mucopolisacaridosis tipo III B es aún desconocida. Debe investigarse la presencia de linfangiectasia intestinal en estos pacientes e iniciar, en caso de confirmarse, un tratamiento dietético adecuado para mejorar así su calidad de vida.

Mucopolysaccharidosis type IIIB is a lysosomal storage disease caused by a deficiency of the N-acetyl-alpha-d-glucosaminidase enzyme involved in the catabolism of heparan sulfate, causing its accumulation in various tissues. We present an 8-year-old patient with mucopolysaccharidosis type IIIB, with a history of chronic diarrhea and endoscopic and histological findings compatible with intestinal lymphangiectasia. After a dietary treatment with a low-fat diet supplemented with medium-chain triglyceride, our patient presents clinical improvement until today. The pathogenesis of chronic diarrhea in patients with mucopolysaccharidosis type IIIB is still unknown. The presence of intestinal lymphangiectasia in these patients should be investigated, and appropriate dietary treatment should be initiated, if confirmed, to improve their quality of life.

[Intestinal lymphangiectasia in a patient with Sanfilippo B syndrome]. / Linfangiectasia intestinal en un paciente afectado de síndrome de Sanfilippo B.

Mucopolysaccharidosis type IIIB is a lysosomal storage disease caused by a deficiency of the N-acetyl-alpha-d-glucosaminidase enzyme involved in the catabolism of heparan sulfate, causing its accumulation in various tissues. We present an 8-year-old patient with mucopolysaccharidosis type IIIB, with a history of chronic diarrhea and endoscopic and histological findings compatible with intestinal lymphangiectasia. After a dietary treatment with a low-fat diet supplemented with mediumchain triglyceride, our patient presents clinical improvement until today. The pathogenesis of chronic diarrhea in patients with mucopolysaccharidosis type IIIB is still unknown. The Linfangiectasia intestinal en un paciente afectado de síndrome de Sanfilippo B Intestinal lymphangiectasia in a patient with Sanfilippo B syndrome presence of intestinal lymphangiectasia in these patients should be investigated, and appropriate dietary treatment should be initiated, if confirmed, to improve their quality of life.

La mucopolisacaridosis tipo III B es una enfermedad de depósito lisosomal causada por la deficiencia de la enzima N-acetil-alfad- glucosaminidasa, implicada en el catabolismo del heparán sulfato, que produce su acúmulo en diversos tejidos. Se presenta a un paciente de 8 años, afectado de mucopolisacaridosis tipo III B, con historia de diarrea crónica y hallazgos endoscópicos e histológicos compatibles con linfangiectasia intestinal. Tras tratamiento dietético con restricción de ácidos grasos de cadena larga y rica en triglicéridos de cadena media, presentó mejoría clínica, mantenida hasta la actualidad. La patogenia de la diarrea crónica en pacientes con mucopolisacaridosis tipo III B es aún desconocida. Debe investigarse la presencia de linfangiectasia intestinal en estos pacientes e iniciar, en caso de confirmarse, un tratamiento dietético adecuado para mejorar así su calidad de vida.

Mucopolysacaridosis type iiib misdiagnosed as an autistic spectrum disorder: a case report and literature review / Mucopolissacaridose tipo iii b mal diagnosticada como transtorno de espectro autista: relato de caso e revisão de literatura

ABSTRACT Objective: To report a rare case of mucopolysaccharidosis IIIB in a pediatric patient, with emphasis on the description of the clinical manifestations and the early diagnosis. Case description: A 14-year-old male patient, who presented regression of neuropsychomotor development since his three years and six months old, with speech loss and frequent falls, evolving with behavioral changes, with agitation and aggressiveness. Although being diagnosed with autism, there was no response to the established treatment; he was subsequently submitted to metabolic investigation, which lead to the diagnosis of Mucopolysaccharidosis IIIB. Comments: Identifying a metabolic disorder requires connecting multiple signs and symptoms, as well as eliminating other apparent causes. MPS IIIB is a diagnostic challenge, particularly in the early stages and in the absence of a family history of the disease.

RESUMO Objetivo: Relatar o caso raro de um paciente pediátrico com mucopolissacaridose III B, com ênfase na descrição de manifestações clínicas. Descrição do caso: Paciente masculino de 14 anos que, a partir dos 3 anos e 6 meses de idade, apresentou regressão do desenvolvimento neuropsicomotor, com perda da fala e quedas frequentes, evoluindo com alterações comportamentais, agitação e agressividade. Diagnosticado como autista, não obteve resposta ao tratamento estabelecido, sendo posteriormente submetido à investigação metabólica, que evidenciou o diagnóstico de mucopolissacaridose III B. Comentários: A identificação de um distúrbio metabólico exige conectar vários sinais e sintomas, além de eliminar outras causas aparentes. A mucopolissacaridose III B é um desafio diagnóstico, particularmente nos estágios iniciais e na ausência de história familiar da doença.

MUCOPOLYSACARIDOSIS TYPE IIIB MISDIAGNOSED AS AN AUTISTIC SPECTRUM DISORDER: A CASE REPORT AND LITERATURE REVIEW.

OBJECTIVE: To report a rare case of mucopolysaccharidosis IIIB in a pediatric patient, with emphasis on the description of the clinical manifestations and the early diagnosis. CASE DESCRIPTION: A 14-year-old male patient, who presented regression of neuropsychomotor development since his three years and six months old, with speech loss and frequent falls, evolving with behavioral changes, with agitation and aggressiveness. Although being diagnosed with autism, there was no response to the established treatment; he was subsequently submitted to metabolic investigation, which lead to the diagnosis of Mucopolysaccharidosis IIIB. COMMENTS: Identifying a metabolic disorder requires connecting multiple signs and symptoms, as well as eliminating other apparent causes. MPS IIIB is a diagnostic challenge, particularly in the early stages and in the absence of a family history of the disease.

Estimated birth prevalence of mucopolysaccharidoses in Brazil.

Several studies have been published on the frequency of the mucopolysaccharidoses (MPS) in different countries. The objective of the present study was to estimate the birth prevalence (BP) of MPS in Brazil. MPS diagnosis registered at MPS-Brazil Network and in Instituto Vidas Raras were reviewed. BP was estimated by (a) the number of registered patients born between 1994 and 2015 was divided by the number of live births (LBs), and (b) a sample of 1,000 healthy individuals was tested for the most frequent variant in IDUA gene in MPS I (p.Trp402Ter) to estimate the frequency of heterozygosity and homozygosity. (a) The BP based on total number of LBs was (cases per 100,000 LBs): MPS overall: 1.25; MPS I: 0.24; MPS II: 0.37; MPS III: 0.21; MPS IV: 0.14; MPS VI: 0.28; MPS VII: 0.02. (b) The overall frequency of p.Trp402Ter was 0.002. Considering the frequency of heterozygotes for the p.Trp402Ter IDUA variant in the RS state, the frequency of this variant among MPS I patients and the relative frequency of the different MPSs, we estimated the birth prevalence of MPS in total and of each MPS type, as follows: MPS overall: 4.62; MPS I: 0.95; MPS II: 1.32; MPS III: 0.56; MPS IV: 0.57; MPS VI: 1.02; MPS VII: 0.05. This study provided original data about BP and relative frequency of the MPS types, in Brazil, based on the frequency of the commonest IDUA pathogenic variant and in the records of two large patient databases.

Molecular characterization of a large group of Mucopolysaccharidosis type IIIC patients reveals the evolutionary history of the disease.

Mucopolysaccharidosis type IIIC (MPSIIIC) is a severe, rare autosomal recessive disorder caused by variants in the heparan-α-glucosaminide N-acetyltransferase (HGSNAT) gene which result in lysosomal accumulation of heparan sulfate. We analyzed clinical presentation, molecular defects and their haplotype context in 78 (27 novel) MPSIIIC cases from 22 countries, the largest group studied so far. We describe for the first time disease-causing variants in the patients from Brazil, Algeria, Azerbaijan, and Iran, and extend their spectrum within Canada, Colombia, Turkey, and the USA. Six variants are novel: two missense, c.773A>T/p.N258I and c.1267G>T/p.G423W, a nonsense c.164T>A/p.L55*, a splice-site mutation c.494-1G>A/p.[P165_L187delinsQSCYVTQAGVRWHHLGSLQALPPGFTPFSYLSLLSSWNC,P165fs], a deletion c.1348delG/p.(D450fs) and an insertion c.1479dupA/p.(Leu494fs). The missense HGSNAT variants lacked lysosomal targeting, enzymatic activity, and likely the correct folding. The haplotype analysis identified founder mutations, p.N258I, c.525dupT, and p.L55* in the Brazilian state of Paraiba, c.493+1G>A in Eastern Canada/Quebec, p.A489E in the USA, p.R384* in Poland, p.R344C and p.S518F in the Netherlands and suggested that variants c.525dupT, c.372-2G>A, and c.234+1G>A present in cis with c.564-98T>C and c.710C>A rare single-nucleotide polymorphisms, have been introduced by Portuguese settlers in Brazil. Altogether, our results provide insights into the origin, migration roots and founder effects of HGSNAT disease-causing variants, and reveal the evolutionary history of MPSIIIC.

Polymorphic variants (p.Ser141Ser and p.Arg737Gly) at the NAGLU gene are really indicative of pseudodeficiency alleles?

Filocamo et al. recently published a paper describing the presence of a pseudodeficiency allele, constituted by p.Ser141Ser and p.Arg737Gly polymorphisms at the NAGLU gene, which leads to a reduced level of the alpha-N-acetyl-D-glucosaminidase activity. Based on analysis performed in Brazilian patients, using a customized gene panel containing SGSH, NAGLU, HGSNAT and GNS we observed that p.Ser141Ser (rs659497) and p.Arg737Gly (rs86312) variants were present in homozygosis in all of our MPS IIIB patients and in the majority of MPS IIIA, IIIC and IIID patients, and there was no significant decrease of the alpha-N-acetyl-D-glucosaminidase enzyme activity in this group when compared with those without the "pseudodeficiency allele". Thus, we suggest that these two variants are not producing a pseudodeficiency allele.

Observational Prospective Natural History of Patients with Sanfilippo Syndrome Type B.

OBJECTIVE: To evaluate the natural course of disease progression in patients with Sanfilippo syndrome type B (mucopolysaccharidosis type IIIB), identify potential end points for future therapy trials, and characterize biomarkers related to the disease. STUDY DESIGN: A prospective, multicenter study was conducted. Baseline, 6-month, and 12-month assessments included neurodevelopmental status (Bayley Scales of Infant Development, Third edition), adaptive status (Vineland Adaptive Behavior Scales, Second Edition), volumetric brain magnetic resonance imaging, cerebrospinal fluid heparan sulfate, and urine glycosaminoglycan (GAG) measurements. RESULTS: Nineteen patients aged 1.6-31.7 years were enrolled. Over 12 months, cognition, adaptive behavior, and cortical gray matter volume (GMV) declined in most patients. For patients diagnosed at <6 years, although there was no overall mean change over 12 months, there were 10%-48%, 3%-66%, and 1%-14% decreases in cognitive development quotient score, Vineland Adaptive Behavior Scales, Second Edition development quotient score, and cortical GMV in 8/12, 9/11, and 10/11 patients, respectively. Mean urine GAG and cerebrospinal fluid heparan sulfate levels were stable, but patients diagnosed at <6 years (n = 14) had higher levels than those ≥6 years at diagnosis (n = 4), which was likely associated with age as they also were generally younger. CONCLUSIONS: Cognition, adaptive behavior, and cortical GMV measures sensitively tracked deterioration in patients with mucopolysaccharidosis type IIIB aged ≤8.6 years. Biomarkers may have prognostic value, but their sensitivity to disease progression requires further investigation. These findings should help evaluate enzyme replacement and gene therapy agents for this rare, devastating, neurodegenerative disease. TRIAL REGISTRATION: ClinicalTrials.gov: NCT01509768.

Molecular defects identified by whole exome sequencing in a child with atypical mucopolysaccharidosis IIIB.

BACKGROUND: Mucopolysaccharidosis IIIB (MPS IIIB) is a genetic disease characterized by mutations in the NAGLU gene, deficiency of α-N-acetylglucosaminidase, multiple congenital malformations and an increased susceptibility to malignancy. Because of the slow progressive nature of this disease and its atypical symptoms, the misdiagnosis of MPS IIIB is not rare in clinical practice. This misdiagnosis could be avoided by using next-generation sequencing (NGS) techniques, which have been shown to have superior performance for detecting mutations underlying rare inherited disorders in previous studies. CASE PRESENTATION: Whole exome sequencing (WES) was conducted and the putative pathogenic variants were validated by Sanger sequencing. The activity of MPS IIIB related enzyme in the patient's blood serum was assayed. A heterozygous, non-synonymous mutation (c.1562C>T, p.P521L) as well as a novel mutation (c.1705C>A, p.Q569K) were found in the NAGLU gene of the patient. The two mutations were validated by Sanger sequencing. Our data showed that this patient's c.1562C>T, p.P521L mutation in the NAGLU gene was inherited from his father and c.1705C>A, p.Q569K was from his mother. The diagnosis was further confirmed by an enzymatic activity assay after patient recall and follow-up. CONCLUSIONS: Our results describe an atypical form of MPS IIIB and illustrate the diagnostic potential of targeted WES in Mendelian disease with unknown etiology. WES could become a powerful tool for molecular diagnosis of MPS IIIB in clinical setting.

Genética clínica comunitaria: exploración de patología genética en Boyacá, Colombia / Clinical community genetics: exploring genetic disorders in Boyacá, Colombia

RESUMEN Objetivo Explorar la presencia de patología genética sindrómica en el Departamento de Boyacá, mediante un acercamiento de medicina genética comunitaria. Materiales y Métodos Un grupo conformado por genetistas, neurólogo pediátrico y genetista bioquímico, llevó a cabo jornadas clínicas en las cuales se evaluaron pacientes con sospecha de enfermedad genética. Se obtuvieron datos demográficos, epidemiológicos y clínicos y se realizó el cálculo de frecuencias de los mismos. En los centros de referencia visitados se realizaron actividades de capacitación al personal médico. Resultados Se encontraron dos agrupamientos genéticos: MPSIII y Síndrome de Ellis Van Creveld, con incidencias mayores a lo reportado en la literatura, además una alta frecuencia de patologías de herencia autosómica recesiva, así como sospecha de síndromes de microdeleción-microduplicación. Conclusiones Se deben establecer mecanismos no convencionales de atención médica para facilitar el acceso a las comunidades a un diagnóstico y tratamiento adecuados en genética. Se espera que el apoyo brindado a los pacientes, familias y personal asistencial de los hospitales a través de las jornadas clínicas y la capacitación, permitan alcanzar este objetivo y a la vez sea un punto de inicio de procesos de prevención primaria y secundaria.(AU)

ABSTRACT Objectives To explore the incidence of syndromic genetic pathologies in Boyacá, Colombia, through a community genetics approach. Materials and Methods A group made up by different medical specialists (geneticists, a pediatric neurologist, and a biochemical geneticist) developed clinical campaigns, in which patients with clinical suspicion of genetic diseases were involved. Demographic, epidemiological and clinical data were collected, and frequency calculations were made based on the collected data. Several training workshops for health personnel were done in each center visited. Results Two genetic clusters were found: mucopolysaccharidosis type III, and Ellis-Van Creveld Syndrome, both of them with higher incidences than those found in the literature. Also, a high frequency of autosomal recessive diseases was found, as well as microdeletion/microduplication syndromes. Conclusions Conventional mechanisms of medical attention must be established, in order to facilitate the access to an appropriate diagnosis and treatment. This work intended to provide support to patients, families and health care services personnel through the workshops and clinical campaigns, and to become a starting point to develop primary and secondary prevention processes.(AU)

Natural History of Sanfilippo Syndrome Type C in Boyacá, Colombia.

Mucopolysaccharidosis type III, or Sanfilippo syndrome, is an autosomal recessive disorder characterized by impairment in the degradation of Heparan sulfate. Here the authors describe the natural history of 5 related individuals; all associated through a large pedigree which reports a total of 11 affected members, originally from the Boyacá region in Colombia, diagnosed with MPS IIIC who all harbor a novel mutation in HGSNAT. The authors report an unusually high incidence of the disease in this population. The clinical features are similar to previously described patients, although some differences in the degree of severity and end-stage of the disease are seen in this specific group. The authors consider that the high degree of endogamy in this specific population could underlie modifying factors for the severity of presentation in these patients. Future studies might provide more information on the functional effect of this novel mutation, which could define this group as a genetic isolate.

Mucopolisacaridosis (síndrome de Hunter) / Mucopolysaccharidosis (Hunter syndrome)

Se realiza una presentación de un caso interesante, no comúnmente visto en la práctica médica, de unos de los tipos de mucopolisacaridosis, específicamente de un síndrome de Hunter. Se hace esta presentación con el objetivo de dar a conocer a estudiantes y profesionales de la salud, mediante fotos, las características físicas del paciente con dicho sídrome, quien llegó desnutrido al hospital; se le operó de la hernia umbilical y se mejoró su estado nutricional al compensarse su hepatopatía. Se le da el alta médica en mejores condiciones(AU)

We present here an interesting case of mucopolysaccharidoses, which is not commonly seen in medical practice, specifically a Hunter syndrome. This presentation is done in order to make known to students and health professionals, through photos, the physical characteristics of the patient with such syndrome. This patient arrived malnourished at the hospital, he was operated on the umbilical hernia and improved his nutritional status by compensating for his liver disease. This patient had medical discharge in better conditions(AU)

A Prospective Natural History Study of Mucopolysaccharidosis Type IIIA.

OBJECTIVES: To characterize the clinical course of mucopolysaccharidosis type IIIA (MPS IIIA), and identify potential endpoints for future treatment trials. STUDY DESIGN: Children with a confirmed diagnosis of MPS IIIA, functioning above a developmental age of 1 year, were followed for up to 2 years. Cognitive status and brain atrophy were assessed by standardized tests and volumetric magnetic resonance imaging, respectively. Liver and spleen volumes and cerebrospinal fluid and urine biomarker levels were measured. RESULTS: Twenty-five children, from 1.1 to 18.4 years old, were enrolled, and 24 followed for at least 12 months. 19 exhibited a rapidly progressing (RP) form of MPS IIIA, and 5, a more slowly progressing form. Children with RP plateaued in development by 30 months, followed by rapid regression after 40-50 months. In patients with RP, cognitive developmental quotients showed consistent steep declines associated with progressive cortical gray matter atrophy. Children with slowly progressing had a similar but more prolonged course. Liver and spleen volumes were approximately double normal size, and cerebrospinal fluid and urine heparin sulfate levels were elevated and relatively constant over time. CONCLUSION: Developmental quotient and cortical gray matter volume are sensitive markers of disease progression in MPS IIIA, and may have utility as clinical endpoints in treatment trials. For optimal outcomes, treatment may need to be instituted in children before the onset of steep cognitive decline and brain atrophy. TRIAL REGISTRATION: ClinicalTrials.gov: NCT01047306.