Exome Sequencing Reveals Biallelic Mutations in MBTPS1 Gene in a Girl with a Very Rare Skeletal Dysplasia.

The Kondo-Fu type of spondyloepiphyseal dysplasia (SEDKF) is a rare skeletal dysplasia caused by homozygous or compound heterozygous mutations in the MBTPS1 gene. The MBTPS1 gene encodes a protein that is involved in the regulation of cholesterol and fatty acid metabolism. Mutations in MBTPS1 can lead to reduced levels of these lipids, which can have a number of effects on development, including skeletal anomalies, growth retardation, and elevated levels of blood lysosomal enzymes. This work reports the case of a 5-year-old girl with SEDKF. The patient had a severely short stature and a number of skeletal anomalies, including kyphosis, pectus carinatum, and reduced bone mineral density. She also had early onset cataracts and inguinal hernias. Genetic testing revealed two novel compound heterozygous variants in the MBTPS1 gene. These variants are predicted to disrupt the function of the MBTPS1 protein, which is consistent with the patient's clinical presentation. This case report adds to the growing body of evidence that mutations in the MBTPS1 gene are causal of SEDKF. We summarized the features of previous reported cases (with age ranges from 4 to 24 years) and identified that 80% had low stature, 70% low weight, 80% had bilateral cataracts and 70% showed Spondyloepiphyseal dysplasia on X-rays. The findings of this study suggest that SEDKF is a clinically heterogeneous disorder that can present with a variety of features. Further studies are needed to better understand the underlying mechanisms of SEDKF and to develop more effective treatments.

Novel frameshift mutation in PURA gene causes severe encephalopathy of unclear cause.

BACKGROUND: The etiology of many genetic diseases is challenging. This is especially true for developmental disorders of the central nervous system, since several genes can be involved. Many of such pathologies are considered rare diseases, since they affect less than 1 in 2000 people. Due to their low frequency, they present several difficulties for patients, from the delay in the diagnosis to the lack of treatments. Next-generation sequencing techniques have improved the search for diagnosis in several pathologies. Many studies have shown that the use of whole-exome/genome sequencing in rare Mendelian diseases has a diagnostic yield between 30% and 50% depending on the disease. METHODS: Here, we present the case of an undiagnosed 6-year-old boy with severe encephalopathy of unclear cause, whose etiological diagnosis was achieved by whole-genome sequencing. RESULTS: We found a novel variant that has not been previously reported in patients nor it has been described in GnomAD. Segregation analysis supports a de novo mutation, since it is not present in healthy parents. The change is predicted to be harmful to protein function, since it falls in the first quarter of the protein producing an altered reading frame and generating a premature stop codon. Additionally, the variant is classified as pathogenic according to ACMG criteria (PVS1, PM2, and PP3). Furthermore, there are several reported frameshift mutations in nearby codons as well as nonsense mutations that are predicted as pathogenic in other studies. CONCLUSION: We found a novel de novo frameshift mutation in the PURA gene (MIM number 600473), c.151_161del, with sufficient evidence of its pathogenicity.

Deep sequencing discovery of causal mtDNA mutations in a patient with unspecific neurological disease.

Mitochondrial diseases (MD) are a group of diseases that can be caused by either mutations in the mitochondrial genome or nuclear DNA. MD may be difficult to diagnose since very often they are highly heterogeneous and with overlapping phenotypes. Molecular genomics approaches, especially NGS have helped in this sense. In this study we have sequenced the mitochondrial genome of a girl with an unspecific neurological disorder and her mother. The later, while neurologically unaffected, suffers from a myopathy without clear cause. We were able to detect two non-synonymous mutations in the MT-ATP6 gene, which we propose are strong candidates for causative agents. 9017C as the main candidate present at high heteroplasmy frequency in the patient (83,2%) and moderate in the mother (45,4%) while it has a low frequency in the general population. It might act alone or in conjunction with 9010A as an accessory mutation. Evolutionary analysis showed that both mutations were located in a critical position in the F0 a subunit, from F0-F1 ATPase. Functional studies showed that carriers of those mutations in comparison to an unaffected individual (father) presented a decrease in the basal and ATP-dependent oxygen consumption rate and a decrease in the maximum respiration rate.

3697G>A in MT-ND1 is a causative mutation in mitochondrial disease.

Mitochondrial diseases are a group of clinically heterogeneous disorders that can be difficult to diagnose. We report a two and a half year old girl with clinical symptoms compatible with Leigh disease but with no definitive diagnosis. Using next generation sequencing we found that mutation 3697G>A was responsible for the patient's clinical symptoms. Corroboration was performed via segregation analysis in mother and sister and by evolutionary analysis that showed that the mutation is located in a highly conserved region across a wide range of species. Functional analyses corroborated the mutation effect and indicated that the pathophysiological alterations were partially restored by Coenzyme Q10. In addition, we proposed that the presence of the mutation at high frequencies causes the phenotype in the patient, while other family members with intermediate levels of heteroplasmy are symptoms-free.

Enfermedad de Pompe: primer caso de inicio en el adulto descrito en Uruguay confirmado genéticamente / Pompe’s Disease: first genetically confirmed case with adult onset reported in Uruguay

La enfermedad de Pompe (EP), también conocida como déficit de maltasa ácida y glucogenosis tipo II, es una enfermedad por depósito de glucógeno consecuencia del déficit de la enzima alfa glicosidasa ácida lisosomal (GAA), no obstante, alteraciones en los mecanismos de autofagia también determinan la patogenia de la enfermedad. Sus manifestaciones son principalmente a nivel del músculo esquelético y cardíaco aunque también hay compromiso extramuscular. La misma es de evolución progresiva y con un patrón de herencia autosómico recesivo. Existen dos formas clínicas principales que son la EP infantil, con o sin miocardiopatía y la forma de inicio tardío. El diagnóstico se realiza demostrando la actividad descendida de la GAA con la técnica de la gota de sangre seca, complementando con un segundo análisis de la actividad enzimática o análisis genético. El tratamiento disponible actualmente es la terapia de remplazo enzimático con GAA recombinante humana (rhGAA). Se describe el primer caso de Enfermedad de Pompe en el adulto en Uruguay confirmado genéticamente.

Pompe disease in Uruguay. The first case in an adult genetically confirmed. Pompe disease, also known as type II glycogenosis, is a progressive autosomal recesive glycogen storage disease caused by a deficiency of lysosomal acid-a-glucosidase (GAA), primarily in skeletal and cardiac muscle, and by defects in autophagy, with an age of onset ranging from infancy through adulthood. In adult onset the tipical presentation is with a limb girdle dystrophy pattern (that engaged especially the hip girdle) or dyspnea secondary to diaphragm weakness. A simple blood-based assay to measure the level of α-glucosidase activity, like dried blood spot test, is the optimal initial test and is needed a second test to confirm the disease (alpha glucosidasa activity in cultured fibroblast or muscle tissue or by genetic testing). An early diagnosis of Pompe disease will improve patient outcomes as care standards including enzyme replacement therapy can be applied and complications can be anticipated. The introduction of enzyme replacement therapy for GAA deficiency using recombinant human GAA (rhGAA) changed the course of the disease with an improvement especially in infantile forms but also in late onset Pompe disease. We describe our first case of adult onset Pompe disease in Uruguay.

Limitaciones de los estudios de genética molecular en el proceso diagnóstico de fibrosis quística / Limitations to molecular genetics studies during the cystic fibrosis diagnostic process

Introducción: la fibrosis quística (FQ) es una enfermedad hereditaria autosómica recesiva causada por mutaciones en el gen que codifica una proteína con función de canal de cloruro (CFTR). Se manifiesta como una enfermedad multiorgánica y se caracteriza por una gran heterogeneidad clínica. Existen pacientes que no manifiestan las características clínicas de la forma clásica y se describen como FQ atípica o no clásica. El diagnóstico se basa en unfenotipo clínico consistente más evidencia de disfunción del canal CFTR y/o en la identificación de dos mutaciones causantes de FQ. Ninguna de estas definiciones es suficientepor sí misma para establecer el diagnóstico. Objetivos: mostrar algunas limitaciones de los estudios de genética molecular en el proceso diagnóstico de FQ. Material y método: se consideran cinco casos clínicos de niños referidos con dato clínico de probable FQ y solicitud de estudio genético para la confirmación diagnóstica. Resultados: los estudios realizados no permiten confirmar el diagnóstico de FQ ni descartar un posible diagnóstico de FQ atípica. Conclusiones: la mayoría de las veces el diagnóstico de FQ es claro y los estudios genéticos permiten la confirmación diagnóstica, el asesoramiento genético y eventual diagnóstico prenatal. Sin embargo, el uso y la interpretación de los análisis genéticos presentan diversasdificultades relacionadas con la condición clínico-paraclínica del paciente, las limitaciones técnicas y la elección del conjunto de mutaciones a ser analizadas, especialmente en los casos de FQ atípica. Este trabajo muestra el desafío que puede implicar para el clínico interpretar un resultado molecular e integrarlo en el proceso diagnóstico de FQ.

Introduction: cystic fibrosis is an autosomal recessive hereditary disease caused by mutations of the gene whichencodes a protein with a CFTR chloride channel function. It appears as a multi-organ disease and is characterized bya great clinical heterogeneity. There are patients who do not evidence the classic clinical characteristics and aredescribed as atypical or non-classic cystic fibrosis. Diagnosis is based on a consistent clinical phenotype andevidence of dysfunction in the CFTR channel and/or in the identification of two mutations causing cystic fibrosis.None of these definitions is enough in itself to confirm diagnosis. Objectives: to show a few limitations on the molecular genetic studies in the cystic fibrosis diagnostic process. Method: five clinical cases of children referred withclinical data of probable cystic fibrosis were considered, and they were requested a genetic study to confirm diagnosis. Results: studies conducted do not enable the confirmation of cystic fibrosis diagnosis and neither do theyallow discarding a possible diagnosis of atypical cystic fibrosis. Conclusions: in most cases the diagnosis of cysticfibrosis is clear and genetic studies enable the confirmation of diagnosis, genetic counseling and the final prenataldiagnosis. However, use and interpretation of genetic analysis result in several difficulties regarding the clinical and paraclinical characteristics of patients, technical limitations and choosing the mutations to be analysed, especially in the case of atypical cystic fibrosis. The present study shows the challenge faced by clinicians when interpreting a molecular result to incorporate it into the cystic fibrosis diagnostic process.

Introdução: a fibrose cística FC é uma doença hereditária autossômica recessiva causada por mutações no gene que codifica uma proteína com função nos canais de cloretos CFTR. É uma doença com manifestações múltiplas e se caracteriza por apresentar-se com grande variedade clínica. Alguns pacientes não apresentam as características clínicas clássicas e nesses casos a doença é chamada FC atípica ou não clássica. O diagnóstico é feito através do fenótipo clínico mais consistente associado a evidencia de disfunção do canal CFTR e/ou na identificação de duas mutações causadoras da FC. Nenhuma dessas definições é suficiente para estabelecer o diagnóstico. Objetivos: mostrar algumas limitações dos estudos de genética molecular no diagnóstico de FC.Material e método: são discutidos cinco casos clínicos de crianças referidas com historia clínica de FC provável e pedido de estudo genético para confirmaçãodo diagnóstico. Resultados: os estudos realizados não permitem confirmaro diagnóstico de FC nem descartar um possível diagnóstico de FC atípica.Conclusões: na maioria dos casos o diagnóstico de FC é claro e os estudos genéticos permitem confirmar odiagnóstico, o assessoramento genético e eventual diagnóstico pré-natal. No entanto, o emprego e a interpretaçãodas análises genéticas apresentam varias dificuldades relacionadas com a condição clínica do paciente, aslimitações técnicas e a escolha do conjunto de mutações a ser estudadas, especialmente nos casos de fibrose cística atípica. Este trabalho mostra o desafio que o médico clínico enfrenta para interpretar um resultado molecular e integrá-lo ao processo de diagnóstico de FC.

Síndrome de Escobar o pterigium múltiple no letal: a propósito de un caso / Escobar's syndrome or nonlethal multiple pterygium: apropos of a case

El síndrome de Escobar o pterigium múltiple no letal es una afección poco frecuente de la cual se han reportado alrededor de 100 casos. Es una entidad de etiología genética con mecanismo de herencia autosómica recesiva cuya fisiopatología aún se desconoce. Clínicamente se caracteriza por pterigium múltiple en cuello y articulaciones, contracturas articulares, restricción del crecimiento intrauterino y posnatal, alteraciones esqueléticas y otras malformaciones de frecuencia variable. En el presente trabajo se describe un caso de síndrome de Escobar. El paciente se examinó por primera vez a los 5 meses de edad. El examen clínico permitió postular una etiología genética pero no se estableció un diagnóstico nosológico. El estudio cromosómico fue normal. El fenotipo clínico completó su definición con la edad; en este sentido, algunos elementos de incipiente manifestación, como el pterigium (pilar fundamental para el diagnóstico), se hizo más evidente -así como otras características faciales- que permitieron, al evaluarlo por tercera vez a los 10 años de edad, establecer el diagnóstico nosológico de síndrome de Escobar. La secuenciación del gene CHRNG no mostró alteraciones genéticas moleculares que puedan relacionarse con el fenotipo observado. El paciente no presenta limitaciones físicas de entidad, ni dificultades de aprendizaje o en su interacción social.

Escobar or nonlethal multiple pterygium syndrome is a rare affection with a total of approximately 100 cases reported. It is a genetic autosomal recessive disorder whose pathophysiology is still unknown. Clinically, it is characterized by multiple pterygium at neck and articulations, articulate contractures, intrauterine and postnatal growth retardation, skeletal alterations and other malformations of variable frequency. Here a patient with Escobar Syndrome is described. The patient was first examined at 5 months of age. Clinical examination suggested a genetic etiology but a definite diagnosis was not established. The cytogenetic study was normal. The clinical phenotype was better defined with age, in this sense; the pterygium (a main clinical feature for the diagnosis) was more evident, as well as other facial features which with a third evaluation at 10 years of age, allowed the establishment of the diagnosis with more certainty. Sequencing of CHRNG gene did not show genetic molecular alterations which could be related with the patient’s phenotype. The patient does not present severe physical limitations nor learning difficulties or problems in his social interaction.