Novel Cases of Non-Syndromic Hearing Impairment Caused by Pathogenic Variants in Genes Encoding Mitochondrial Aminoacyl-tRNA Synthetases.

Dysfunction of some mitochondrial aminoacyl-tRNA synthetases (encoded by the KARS1, HARS2, LARS2 and NARS2 genes) results in a great variety of phenotypes ranging from non-syndromic hearing impairment (NSHI) to very complex syndromes, with a predominance of neurological signs. The diversity of roles that are played by these moonlighting enzymes and the fact that most pathogenic variants are missense and affect different domains of these proteins in diverse compound heterozygous combinations make it difficult to establish genotype-phenotype correlations. We used a targeted gene-sequencing panel to investigate the presence of pathogenic variants in those four genes in cohorts of 175 Spanish and 18 Colombian familial cases with non-DFNB1 autosomal recessive NSHI. Disease-associated variants were found in five cases. Five mutations were novel as follows: c.766C>T in KARS1, c.475C>T, c.728A>C and c.1012G>A in HARS2, and c.795A>G in LARS2. We provide audiograms from patients at different ages to document the evolution of the hearing loss, which is mostly prelingual and progresses from moderate/severe to profound, the middle frequencies being more severely affected. No additional clinical sign was observed in any affected subject. Our results confirm the involvement of KARS1 in DFNB89 NSHI, for which until now there was limited evidence.

Clinical and Genetic Characterization of RDH12-Retinal Dystrophy in a South American Cohort.

PURPOSE: To characterize the largest cohort of individuals with retinol dehydrogenase 12 (RDH12)-retinal dystrophy to date, and the first one from South America. DESIGN: Retrospective multicenter international study. SUBJECTS: Seventy-eight patients (66 families) with an inherited retinal dystrophy and biallelic variants in RDH12. METHODS: Review of clinical notes, ophthalmic images, and molecular diagnosis. MAIN OUTCOME MEASURES: Visual function, retinal imaging, and characteristics were evaluated and correlated. RESULTS: Thirty-seven individuals self-identified as Latino (51%) and 34 as White (47%). Sixty-nine individuals (88%) had Leber congenital amaurosis (LCA)/early-onset severe retinal dystrophy. Macular and midperipheral atrophy were seen in all patients from 3 years of age. A novel retinal finding was a hyperautofluorescent ring in 2 young children with LCA. Thirty-nine patients (50%) had subsequent visits, with mean follow-up of 6.8 ± 7.3 (range, 0-29) years. Eight variants (21%) were previously unreported, and the most frequent variant was c.295C>A, p.Leu99Ile, present in 52 alleles of 32 probands. Individuals with LCA homozygous for p.Leu99Ile (31%) had a later age of onset, a slower rate of best-corrected visual acuity decrease, the largest percentage of patients with mild visual impairment, and were predicted to reach legal blindness at an older age than the rest of the cohort. CONCLUSIONS: By describing the largest molecularly confirmed cohort to date, improved understanding of disease progression was possible. Our detailed characterization aims to support research and the development of novel therapies that may have the potential to reduce or prevent vision loss in individuals with RDH12-associated retinal dystrophy. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures.

Phenotypic characterization of retinitis pigmentosa associated with deafness / Caracterización fenotípica de la retinitis pigmentaria asociada a sordera

Introduction: There are several syndromes that associate retinitis pigmentosa with deafness or hearing loss. The most frequent is Usher syndrome, a genetic disorder of autosomal recessive inheritance, which, in some cases, is accompanied by vestibular dysfunction. However, there are cases of families that despite having retinitis pigmentosa associated with deafness, cannot be classified as Usher or other syndromes due to additional findings. Objective: To reassess the phenotypes of 103 families previously diagnosed as possible Usher syndrome and/or retinitis pigmentosa associated with deafness. Materials and methods: We conducted a descriptive and retrospective study by reviewing the medical records of 103 families with a probable clinical diagnosis of Usher syndrome and/or retinitis pigmentosa associated with deafness. Families whose clinical diagnosis did not correspond to the typical Usher syndrome were selected and evaluated ophthalmologically and audiologically. Demographic and clinical variables were analyzed. Results: We selected and then reevaluated 14 families and 55 individuals as they did not correspond to a clinical diagnosis of Usher syndrome; 13.6% of the families initially considered to have typical Usher syndrome were later diagnosed with retinitis pigmentosa associated with deafness, another ocular symptom associated with hearing loss, retinitis pigmentosa, or isolated hearing loss in the same family. Conclusions: Family studies are essential in cases where the symptoms do not match the typical Usher' syndrome. In the cases of retinitis pigmentosa associated with deafness, a correct clinical diagnosis allows for focusing on the molecular analyses to establish a differential diagnosis. The need for nomenclature guidelines on these atypical findings is relevant to aid physicians and researchers in the best approach to these cases.

Introducción. El síndrome de Usher es una alteración genética caracterizada por la asociación de retinitis pigmentaria y sordera. Sin embargo, hay casos con familias en las cuales, a pesar de presentarse dicha asociación, no se puede diagnosticar un síndrome de Usher ni ninguno otro. Objetivo. Reevaluar fenotípicamente a 103 familias con diagnóstico previo de posible síndrome de Usher o retinitis pigmentaria asociada con sordera. Materiales y métodos. Se revisaron las historias clínicas de 103 familias con un posible diagnóstico clínico de síndrome de Usher o retinitis pigmentaria asociada con sordera. Se seleccionaron las familias cuyo diagnóstico clínico no correspondía a un síndrome de Usher típico. Los afectados fueron valorados oftalmológica y audiológicamente. Se analizaron variables demográficas y clínicas. Resultados. Se reevaluaron 14 familias cuyo diagnóstico clínico no correspondía al de síndrome de Usher. De las familias con diagnóstico inicial de síndrome de Usher típico, el 13,6 % recibieron uno posterior de "retinitis pigmentaria asociada con sordera", de "otro síntoma ocular asociado con hipoacusia", o en forma aislada en una misma familia, de "retinitis pigmentaria" o "hipoacusia". Conclusiones. Es fundamental el estudio familiar en los casos en que la clínica no concuerda con el diagnóstico de síndrome de Usher típico. En los pacientes con retinitis pigmentaria asociada con sordera, el diagnóstico clínico acertado permite enfocar los análisis moleculares y, así, establecer un diagnóstico diferencial. Es necesario elaborar guías de nomenclatura en los casos con estos hallazgos atípicos para orientar a médicos e investigadores en cuanto a su correcto manejo.

Reducing the Clinical and Public Health Burden of Familial Hypercholesterolemia: A Global Call to Action.

Importance: Familial hypercholesterolemia (FH) is an underdiagnosed and undertreated genetic disorder that leads to premature morbidity and mortality due to atherosclerotic cardiovascular disease. Familial hypercholesterolemia affects 1 in 200 to 250 people around the world of every race and ethnicity. The lack of general awareness of FH among the public and medical community has resulted in only 10% of the FH population being diagnosed and adequately treated. The World Health Organization recognized FH as a public health priority in 1998 during a consultation meeting in Geneva, Switzerland. The World Health Organization report highlighted 11 recommendations to address FH worldwide, from diagnosis and treatment to family screening and education. Research since the 1998 report has increased understanding and awareness of FH, particularly in specialty areas, such as cardiology and lipidology. However, in the past 20 years, there has been little progress in implementing the 11 recommendations to prevent premature atherosclerotic cardiovascular disease in an entire generation of families with FH. Observations: In 2018, the Familial Hypercholesterolemia Foundation and the World Heart Federation convened the international FH community to update the 11 recommendations. Two meetings were held: one at the 2018 FH Foundation Global Summit and the other during the 2018 World Congress of Cardiology and Cardiovascular Health. Each meeting served as a platform for the FH community to examine the original recommendations, assess the gaps, and provide commentary on the revised recommendations. The Global Call to Action on Familial Hypercholesterolemia thus represents individuals with FH, advocacy leaders, scientific experts, policy makers, and the original authors of the 1998 World Health Organization report. Attendees from 40 countries brought perspectives on FH from low-, middle-, and high-income regions. Tables listing country-specific government support for FH care, existing country-specific and international FH scientific statements and guidelines, country-specific and international FH registries, and known FH advocacy organizations around the world were created. Conclusions and Relevance: By adopting the 9 updated public policy recommendations created for this document, covering awareness; advocacy; screening, testing, and diagnosis; treatment; family-based care; registries; research; and cost and value, individual countries have the opportunity to prevent atherosclerotic heart disease in their citizens carrying a gene associated with FH and, likely, all those with severe hypercholesterolemia as well.

Genetic association with intravitreal ranibizumab response for neovascular age-related macular degeneration in Hispanic population.

BACKGROUND/PURPOSE: Age-related macular degeneration (AMD) is the leading cause of visual impairment in patients over 55 years. Currently, the most common therapies for neovascular AMD (nAMD) are intravitreal antiangiogenics. Studies suggest that genetic factors influence on antiangiogenics therapy outcomes. The purpose of this work was to establish the association between complement factor H (CFH) (Y402H), age-related maculopathy susceptibility 2 (ARMS2) (A69S), and high-temperature requirement factor A1 (HTRA1) (rs11200638) polymorphisms and the response to treatment with ranibizumab in patients with nAMD. METHODS: A cross-sectional study with 61 eyes with nAMD treated with ranibizumab was performed. Association between polymorphisms from CFH, ARMS2, and HTRA1 with the response to treatment was established. RESULTS: The mean age of patients was 76.6 (51-91) years. Only 37.7% of patients had a functional response and 26.2% had an anatomic response. TT polymorphism Y402H from CFH gene was associated with an increased likelihood of functional response to treatment. Otherwise, there was not a statistically significant association between anatomic and functional response to gene polymorphisms rs11200638 from HTRA1 and rs10490924 from ARMS 2. CONCLUSIONS: This study suggests that the response to intravitreal antiangiogenic therapy with ranibizumab was not associated to main polymorphisms from genes HTRA1 and ARMS2. However, it was found that the response to treatment differed according to CFH genotype, suggesting that further investigations are needed to establish if patients with the CC and TC genotype may need to be monitored more closely for disease recurrence than the TT genotype.

Detection of hearing loss in newborns: Definition of a screening strategy in Bogotá, Colombia.

OBJECTIVE: To describe the results from the hearing screening protocol adopted in a Hospital in Colombia emphasizing the importance of performing screening on an outpatient basis, when the newborn is more than 24 h old. METHODS: A prospective study at Hospital Universitario San Ignacio in Bogota, Colombia was carried out, from May 1st, 2016 to Nov 30th, 2017, the study sample included 2.088 newborns examined using transient otoacoustic emissions. RESULTS: We obtained written consent from the parents of 1.523 newborns and 24 individuals (1.6%) failed the first stage of the screening, nine cases unilateral and 15 bilateral. A total of nine neonates (0,6%) failed the second screening test, six cases unilateral and three bilateral. Four (0,3%) did not return to the second test. Our false altered screening rate was 0.7%. CONCLUSIONS: In a developing country with limited human and economic resources, in which newborn early discharge is the norm, a newborn hearing screening program linked to infants' check-ups, that uses otoacoustic emissions after 48 h of life, seems a feasible option compare to the standard US protocol aiming to conduct hearing screening prior to discharge.

Mutational analysis of the LDLR gene in a cohort of Colombian families with familial hypercholesterolemia.

BACKGROUND AND AIMS: Familial hypercholesterolemia (FH) is characterized by elevated serum cholesterol levels due to high low-density lipoprotein (LDL) cholesterol levels. FH is an autosomal dominant genetic disorder and one of the most common dominant hereditary diseases in the world. However, the frequency of mutations in Colombia is unknown. The purpose of this preliminary study was to identify mutations in the LDL receptor (LDLR) gene in a Colombian population with FH. METHODS: The study included 24 families with clinical diagnosis of sure/probable FH. The 18 exons of the LDLR were sequenced by Sanger method. RESULTS: Among 18 variants identified, 3 were known pathogenic mutations and were identified in nine individuals in five unrelated families. Five affected individuals were heterozygous for one mutation each. They were the p.W4X in two, the p.D139G in two and the p.G396D in one. Two affected individuals were homozygous for p.G396D. The variant c.1187-1G > T, which has uncertain significance in FH pathogenesis, was present in all the individuals with the p.D139G mutation. CONCLUSIONS: In total, 18 variants were identified, of which 14 correspond to known nonpathogenic variants. Three pathogenic variants were identified in the LDLR. No pathological mutations were identified in the LDLR in 79% of the study population.

Caracterización fenotípica de la retinitis pigmentaria asociada a sordera / Phenotypic characterization of retinitis pigmentosa associated with deafness

Introducción. El síndrome de Usher es una alteración genética caracterizada por la asociación de retinitis pigmentaria y sordera. Sin embargo, hay casos con familias en las cuales, a pesar de presentarse dicha asociación, no se puede diagnosticar un síndrome de Usher ni ninguno otro. Objetivo. Reevaluar fenotípicamente a 103 familias con diagnóstico previo de posible síndrome de Usher o retinitis pigmentaria asociada con sordera. Materiales y métodos. Se revisaron las historias clínicas de 103 familias con un posible diagnóstico clínico de síndrome de Usher o retinitis pigmentaria asociada con sordera. Se seleccionaron las familias cuyo diagnóstico clínico no correspondía a un síndrome de Usher típico. Los afectados fueron valorados oftalmológica y audiológicamente. Se analizaron variables demográficas y clínicas. Resultados. Se reevaluaron 14 familias cuyo diagnóstico clínico no correspondía al de síndrome de Usher. De las familias con diagnóstico inicial de síndrome de Usher típico, el 13,6 % recibieron uno posterior de "retinitis pigmentaria asociada con sordera" de "otro síntoma ocular asociado con hipoacusia',' o en forma aislada en una misma familia, de "retinitis pigmentaria" o "hipoacusia'.' Conclusiones. Es fundamental el estudio familiar en los casos en que la clínica no concuerda con el diagnóstico de síndrome de Usher típico. En los pacientes con retinitis pigmentaria asociada con sordera, el diagnóstico clínico acertado permite enfocar los análisis moleculares y, así, establecer un diagnóstico diferencial. Es necesario elaborar guías de nomenclatura en los casos con estos hallazgos atípicos para orientar a médicos e investigadores en cuanto a su correcto manejo.

Introduction: There are several syndromes that associate retinitis pigmentosa with deafness or hearing loss. The most frequent is Usher syndrome, a genetic disorder of autosomal recessive inheritance, which, in some cases, is accompanied by vestibular dysfunction. However, there are cases of families that despite having retinitis pigmentosa associated with deafness, cannot be classified as Usher or other syndromes due to additional findings. Objective: To reassess the phenotypes of 103 families previously diagnosed as possible Usher syndrome and/or retinitis pigmentosa associated with deafness. Materials and methods: We conducted a descriptive and retrospective study by reviewing the medical records of 103 families with a probable clinical diagnosis of Usher syndrome and/or retinitis pigmentosa associated with deafness. Families whose clinical diagnosis did not correspond to the typical Usher syndrome were selected and evaluated ophthalmologically and audiologically. Demographic and clinical variables were analyzed. Results: We selected and then reevaluated 14 families and 55 individuals as they did not correspond to a clinical diagnosis of Usher syndrome; 13.6% of the families initially considered to have typical Usher syndrome were later diagnosed with retinitis pigmentosa associated with deafness, another ocular symptom associated with hearing loss, retinitis pigmentosa, or isolated hearing loss in the same family. Conclusions: Family studies are essential in cases where the symptoms do not match the typical Usher' syndrome. In the cases of retinitis pigmentosa associated with deafness, a correct clinical diagnosis allows for focusing on the molecular analyses to establish a differential diagnosis. The need for nomenclature guidelines on these atypical findings is relevant to aid physicians and researchers in the best approach to these cases.

[Phenotypic and molecular characterization of a Colombian family with phenylketonuria].

INTRODUCTION: Phenylketonuria is a metabolic disorder characterized by severe neurological involvement and behavioral disorder, whose early diagnosis enables an effective treatment to avoid disease sequelae, thus changing the prognosis. Objective: To characterize a family with phenylketonuria in Colombia at clinical, biochemical and molecular levels. Materials and methods: The population consisted of seven individuals of a consanguineous family with four children with suggestive symptoms of phenylketonuria. After signing an informed consent, blood and urine samples were taken for colorimetric tests and high performance liquid and thin layer chromatographies. DNA extraction and sequencing of the 13 exons of the PAH gene were performed in all subjects. We designed primers for each exon with the Primer 3 software using automatic sequencing equipment Abiprism 3100 Avant. Sequences were analyzed using the SeqScape, v2.0, software. Results: We described the clinical and molecular characteristics of a Colombian family with phenylketonuria and confirmed the presence of the mutation c.398_401delATCA. We established a genotype-phenotype correlation, highlighting the interesting clinical variability found among the affected patients despite having the same mutation in all of them. Conclusions: Early recognition of this disease is very important to prevent its neurological and psychological sequelae, given that patients reach old age without diagnosis or proper management.

[Mutational frequencies in usherin(USH2A gene) in 26 Colombian individuals with Usher syndrome type II]. / Frecuencia de mutaciones en el gen de la usherina (USH2A) en 26 individuos colombianos con síndrome de Usher, tipo II.

INTRODUCTION: Usher syndrome is a disorder characterized by progressive retinitis pigmentosa, prelingual sensory hearing loss and vestibular dysfunction. It is the most frequent cause of deaf-blindness in humans. Three clinical types and twelve genetic subtypes have been characterized. Type II is the most common, and among these cases, nearly 80% have mutations in the USH2A gene. OBJECTIVE: The aim of the study was to establish the mutational frequencies for the short isoform of USH2A gene in Usher syndrome type II. MATERIALS AND METHODS: Twenty-six Colombian individuals with Usher syndrome type II were included. SSCP analysis for 20 exons of the short isoform was performed and abnormal patterns were sequenced. Sequencing of exon 13 of the USH2A gene was performed for all the individuals because the most frequent mutation is located in this exon. RESULTS: The most frequent mutation was c.2299delG, identified in the 27% (n=8) of the sample. The second mutation, p.R334W, showed a frequency of 15%. A new variant identified in the 5'UTR region, g.129G>T, was present in 1 individual (4%). Four polymorphisms were identified; one of them is a new deletion in exon 20, first reported in this study. CONCLUSIONS: Mutations in the usherin short isoform were identified in 38% of a sample of 26 USH2 cases. Molecular diagnosis was established in 7 of the 26.

Caracterización fenotípica y molecular de una familia colombiana con fenilcetonuria / Phenotypic and molecular characterization of a Colombian family with phenylketonuria

Introducción. La fenilcetonuria es un trastorno metabólico caracterizado por un compromiso neurológico grave y por alteraciones del comportamiento. Su diagnóstico temprano permite establecer un tratamiento efectivo que evita las secuelas y modifica el pronóstico. Objetivo. Caracterizar a una familia con fenilcetonuria en Colombia, a nivel clínico, bioquímico y molecular. Materiales y métodos. Se estudió una población de siete individuos de una familia consanguínea en la que cuatro hijos presentaban signos clínicos sugestivos de fenilcetonuria. Una vez firmado el consentimiento informado, se tomaron muestras de sangre y orina para las pruebas colorimétricas, la cromatografía de capa fina y la cromatografía líquida de alta eficacia. Se extrajo el ADN y se secuenciaron los 13 exones del gen PAH de todos los sujetos estudiados. Se diseñaron iniciadores para cada exón con el programa Primer 3; la secuenciación automática se hizo con el equipo Abiprism 3100 Avant y, el análisis de las secuencias, con el programa SeqScape v2.0. Resultados. Se describieron las características clínicas y moleculares de una familia colombiana con fenilcetonuria en la que se identificó la mutación c.398_401delATCA; se presentó una correlación fenotipo-genotipo con una interesante variabilidad clínica entre los afectados, a pesar de tener la misma mutación. Conclusiones. Es importante el reconocimiento temprano de esta enfermedad para evitar sus secuelas neurológicas y psicológicas, pues los pacientes llegan a edades avanzadas sin diagnóstico ni tratamiento adecuados.

Introduction: Phenylketonuria is a metabolic disorder characterized by severe neurological involvement and behavioral disorder, whose early diagnosis enables an effective treatment to avoid disease sequelae, thus changing the prognosis. Objective: To characterize a family with phenylketonuria in Colombia at clinical, biochemical and molecular levels. Materials and methods: The population consisted of seven individuals of a consanguineous family with four children with suggestive symptoms of phenylketonuria. After signing an informed consent, blood and urine samples were taken for colorimetric tests and high performance liquid and thin layer chromatographies. DNA extraction and sequencing of the 13 exons of the PAH gene were performed in all subjects. We designed primers for each exon with the Primer 3 software using automatic sequencing equipment Abiprism 3100 Avant. Sequences were analyzed using the SeqScape, v2.0, software. Results: We described the clinical and molecular characteristics of a Colombian family with phenylketonuria and confirmed the presence of the mutation c.398_401delATCA. We established a genotype-phenotype correlation, highlighting the interesting clinical variability found among the affected patients despite having the same mutation in all of them. Conclusions: Early recognition of this disease is very important to prevent its neurological and psychological sequelae, given that patients reach old age without diagnosis or proper management.

Diagnóstico prénatal: retrospectiva / Diagnóstico prénatal: retrospectiva / Prenatal diagnosis: retrospective

O Diagnóstico Pré-Natal (DPN) é um conjunto de técnicas destinado a investigar a saúde fetal ainda no período de vida intrauterina. é dirigido principalmente a casais com risco aumentado de gerar uma criança com uma anomalia genética ou congenita. Seu objetivo fundamental pressupõe a identificação de anomalias cromossômicas, malformações, doenças metabólicas mendelianas e outras alterações circunstancialmente adquiridas durante a gestação e com repercussões sobre o feto (1-4). O DPN tem sido usado como um método formal de diagnóstico por mais de 45 anos, passando por diferentes fases no seu desenvolvimento. A história do DPN está relacionada com a introdução e o aprimoramento de novas técnicas laboratoriais e diagnósticas. O primeiro passo para o conhecimento do compartimento feto-placentário foi dado por Bevis, em 1952, quando realizou uma amniocentese com fins propedeuticos: o estudo da doença hemolítica fetal. Nos seguintes anos, vários pesquisadores demostraram que é possível determinar o sexo fetal mediante o estudo da cromatina sexual em células de líquido amniótico (5- 8). O desenvolvimento das técnicas cito-genéticas (9) levou a Fuchs e Philips (10) a demonstrar a viabilidade de se cultivar células obtidas no Líquido Amniótico (LA) para posterior análise do cariótipo fetal. Desse modo, obtiveramse os primeiros cariótipos fetais a partir de células de LA entre 1965 e 1967 (11-13). Valenti (14) e Nadler (15) descreveram o primeiro DPN de uma anomalia cromossômica: a trissomia do cromossomo 21. No mesmo ano, diagnosticouse uma anomalia por erro inato do metabolismo (galactosemia) mediante a análise do LA (15). Quatro anos depois, altas dosagens de alfafetoproteína (AFP) no soro materno foram correlacionadas com o aumento da probabilidade de ocorrencia de erros no fechamento do tubo neural (16).

El Diagnóstico Prenatal (DPN) es un conjunto de técnicas destinadas a establecer un diagnóstico fetal aún en el periodo de vida intra-uterina. Está dirigido principalmente a parejas con mayor riesgo de presentar un embarazo de un hijo con una anomalía genética o congénita. Su objetivo fundamental es lograr la identificación de anomalías cromosómicas, malformaciones, enfermedades metabólicas, mendelianas y otras alteraciones eventualmente adquiridas durante la gestación y con repercusiones sobre el feto. El DPN ha sido usado como un método formal de diagnóstico desde hace más de 45 años, pasando por las diferentes fases de su evolución. Esta revisión describe estas fases abordando las realizaciones científicas que permitieron su implementación y mejoramiento continuo.

Prenatal diagnosis is a set of techniques intended to establish a fetal diagnosis even in the period of intrauterine life. It is aimed primarily at couples with higher risk of having a genetic or congenital abnormal pregnancy. Its basic aim is to ensure the identification of chromosomal anomalies, malformations, metabolic and Mendelian diseases, and other alterations eventually acquired during pregnancy which have an impact on the fetus.Prenatal diagnosis has been used as a formal diagnosis method for more than 45 years, going through the various stages of its evolution. This text revises these phases by addressing the scientific and technological developments that have led to its implementation and continuous improvement.

Frecuencia de mutaciones en el gen de la usherina (USH2A) en 26 individuos colombianos con síndrome de Usher, tipo II / Mutational frequencies in usherin (USH2A gene) in 26 Colombian individuals with Usher syndrome type II

Introducción. El síndrome de Usher se caracteriza por hipoacusia neurosensorial congénita, retinitis pigmentaria y disfunción vestibular. Es la causa más frecuente de sordo-ceguera en el mundo. Se divide en tres tipos clínicos y doce subtipos genéticos. El tipo II es la forma más común y cerca de 80 % de los casos corresponden al subtipo 2 del síndrome de Usher. Objetivo. Establecer la frecuencia de mutaciones en la isoforma corta del gen USH2A en individuos colombianos con síndrome de Usher, tipo II. Materiales y métodos. Se estudiaron 26 individuos colombianos con diagnóstico clínico de síndrome de Usher, tipo II. Se hizo análisis de SSCP para los 20 exones que codifican para la isoforma corta y se secuenciaron los patrones anormales. Además, se secuenció el exón 13 en todos los individuos, ya que allí se encuentra la mutación más frecuente de este gen. Resultados. La mutación más frecuente es la c.2299delG, correspondiente al 27 % de la población. La segunda mutación identificada es la p.R334W, con una frecuencia de 15 %. Se identificó un nuevo cambio, el g.129G>T,en la región 5’UTR del gen, correspondiente al 4 % de la población. Se identificaron cuatro cambios polimórficos, uno de ellos es una deleción nueva identificada en el exón 20. Conclusiones. Se logró establecer que, al menos, 38 % de la población analizada con síndrome de Usher, tipo II, presenta alguna mutación en la isoforma corta del gen de la usherina. El diagnóstico molecular se logró establecer en el 23 %.

Introduction. Usher syndrome is a disorder characterized by progressive retinitis pigmentosa, prelingual sensory hearing loss and vestibular dysfunction. It is the most frequent cause of deaf-blindness in humans. Three clinical types and twelve genetic subtypes have been characterized. Type II is the most common, and among these cases, nearly 80% have mutations in the USH2A gene. Objective. The aim of the study was to establish the mutational frequencies for the short isoform of USH2A gene in Usher syndrome type II. Materials and methods. Twenty-six Colombian individuals with Usher syndrome type II were included. SSCP analysis for 20 exons of the short isoform was performed and abnormal patterns were sequenced. Sequencing of exon 13 of the USH2A gene was performed for all the individuals because the most frequent mutation is located in this exon. Results. The most frequent mutation was c.2299delG, identified in the 27% (n=8) of the sample. The second mutation, p.R334W, showed a frequency of 15%. A new variant identified in the 5’UTR region, g.129G>T, was present in 1 individual (4%). Four polymorphisms were identified; one of them is a new deletion in exon 20, first reported in this study. Conclusions. Mutations in the usherin short isoform were identified in 38% of a sample of 26 USH2 cases. Molecular diagnosis was established in 7 of the 26.