Reporte de caso clínico: síndrome CHARGE

Se conoce como síndrome CHARGE a una entidad clínica de origen genético caracterizada por la presencia de: coloboma, defectos cardiacos, atresia de coanas, retraso del crecimiento, hipogonadismo y defectos auditivos. En las dos terceras partes de los casos se debe a la mutación del gen CHD7 en el cromosoma 8. Debido a la baja incidencia y morbilidad variable asociada a esta patología, es importante realizar una revisión adecuada sobre la misma, mediante el estudio de caso diagnosticado clínicamente, con el objetivo de lograr una oportuna detección y manejo de la enfermedad. Se presenta el caso de un paciente masculino de 3 años de edad que presentó las características de dicho síndrome desde una etapa temprana en el desarrollo. El caso fue valorado de acuerdo a los nuevos criterios diagnósticos para la enfermedad, permitiendo la detección temprana y el tratamiento oportuno de las morbilidades asociadas. Se resalta el hecho de que no es fundamental tener todas las características del síndrome para hacer el diagnóstico del mismo, y que lo más importante es identificar las malformaciones que ponen en riesgo la vida del paciente al momento del nacimiento o en los primeros meses. El examen genético es sólo una prueba confirmatoria y el resultado negativo no excluye el diagnóstico.

Deleterious ZNRF3 germline variants cause neurodevelopmental disorders with mirror brain phenotypes via domain-specific effects on Wnt/β-catenin signaling

Zinc and RING finger 3 (ZNRF3) is a negative-feedback regulator of Wnt/β-catenin signaling, which plays an important role in human brain development. Although somatically frequently mutated in cancer, germline variants in ZNRF3 have not been established as causative for neurodevelopmental disorders (NDDs). We identified 12 individuals with ZNRF3 variants and various phenotypes via GeneMatcher/Decipher and evaluated genotype-phenotype correlation. We performed structural modeling and representative deleterious and control variants were assessed using in vitro transcriptional reporter assays with and without Wnt-ligand Wnt3a and/or Wnt-potentiator R-spondin (RSPO). Eight individuals harbored de novo missense variants and presented with NDD. We found missense variants associated with macrocephalic NDD to cluster in the RING ligase domain. Structural modeling predicted disruption of the ubiquitin ligase function likely compromising Wnt receptor turnover. Accordingly, the functional assays showed enhanced Wnt/β-catenin signaling for these variants in a dominant negative manner. Contrarily, an individual with microcephalic NDD harbored a missense variant in the RSPO-binding domain predicted to disrupt binding affinity to RSPO and showed attenuated Wnt/β-catenin signaling in the same assays. Additionally, four individuals harbored de novo truncating or de novo or inherited large in-frame deletion variants with non-NDD phenotypes, including heart, adrenal, or nephrotic problems. In contrast to NDD-associated missense variants, the effects on Wnt/β-catenin signaling were comparable between the truncating variant and the empty vector and between benign variants and the wild type. In summary, we provide evidence for mirror brain size phenotypes caused by distinct pathomechanisms in Wnt/β-catenin signaling through protein domain-specific deleterious ZNRF3 germline missense variants

Reporte de caso clínico: síndrome CHARGE

Se conoce como síndrome CHARGE a una entidad clínica de origen genético caracterizada por la presencia de: coloboma, defectos cardiacos, atresia de coanas, retraso del crecimiento, hipogonadismo y defectos auditivos. En las dos terceras partes de los casos se debe a la mutación del gen CHD7 en el cromosoma 8. Debido a la baja incidencia y morbilidad variable asociada a esta patología, es importante realizar una revisión adecuada sobre la misma, mediante el estudio de caso diagnosticado clínicamente, con el objetivo de lograr una oportuna detección y manejo de la enfermedad. Se presenta el caso de un paciente masculino de 3 años de edad que presentó las características de dicho síndrome desde una etapa temprana en el desarrollo. El caso fue valorado de acuerdo a los nuevos criterios diagnósticos para la enfermedad, permitiendo la detección temprana y el tratamiento oportuno de las morbilidades asociadas. Se resalta el hecho de que no es fundamental tener todas las características del síndrome para hacer el diagnóstico del mismo, y que lo más importante es identificar las malformaciones que ponen en riesgo la vida del paciente al momento del nacimiento o en los primeros meses. El examen genético es sólo una prueba confirmatoria y el resultado negativo no excluye el diagnóstico.

<i>OPA1</i> Dominant Optic Atrophy: Diagnostic Approach in the Pediatric Population

A clinical and genetic study was conducted with pediatric patients and their relatives with optic atrophy 1 (OPA1) mutations to establish whether there is a genotype–phenotype correlation among the variants detected within and between families. Eleven children with a confirmed OPA1 mutation were identified during the study period. The main initial complaint was reduced visual acuity (VA), present in eight patients of the cohort. Eight of eleven patients had a positive family history of optic atrophy. The mean visual acuity at the start of the study was 0.40 and 0.44 LogMAR in the right and left eye, respectively. At the end of the study, the mean visual acuity was unchanged. Optical coherence tomography during the first visit showed a mean retinal nerve fiber layer thickness of 81.6 microns and 80.5 microns in the right and left eye, respectively; a mean ganglion cell layer of 52.5 and 52.4 microns, respectively, and a mean central macular thickness of 229.5 and 233.5 microns, respectively. The most common visual field defect was a centrocecal scotoma, and nine out of eleven patients showed bilateral temporal disc pallor at baseline. Sequencing of OPA1 showed seven different mutations in the eleven patients, one of which, NM_130837.3: c.1406_1407del (p.Thr469LysfsTer16), has not been previously reported. Early diagnosis of dominant optic atrophy is crucial, both for avoiding unnecessary consultations and/or treatments and for appropriate genetic counseling

Whole-Exome Sequencing of 24 Spanish Families: Candidate Genes for Non-Syndromic Pediatric Keratoconus

Keratoconus is a corneal dystrophy that is one of the main causes of corneal transplantation and for which there is currently no effective treatment for all patients. The presentation of this disease in pediatric age is associated with rapid progression, a worse prognosis and, in 15–20% of cases, the need for corneal transplantation. It is a multifactorial disease with genetic variability, which makes its genetic study difficult. Discovering new therapeutic targets is necessary to improve the quality of life of patients. In this manuscript, we present the results of whole-exome sequencing (WES) of 24 pediatric families diagnosed at the University Hospital La Paz (HULP) in Madrid. The results show an oligogenic inheritance of the disease. Genes involved in the structure, function, cell adhesion, development and repair pathways of the cornea are proposed as candidate genes for the disease. Further studies are needed to confirm the involvement of the candidate genes described in this article in the development of pediatric keratoconus

Snijders Blok–Campeau Syndrome: Description of 20 Additional Individuals with Variants in <i>CHD3</i> and Literature Review

Snijders Blok–Campeau syndrome (SNIBCPS, OMIM# 618205) is an extremely infrequent disease with only approximately 60 cases reported so far. SNIBCPS belongs to the group of neurodevelopmental disorders (NDDs). Clinical features of patients with SNIBCPS include global developmental delay, intellectual disability, speech and language difficulties and behavioral disorders like autism spectrum disorder. In addition, patients with SNIBCPS exhibit typical dysmorphic features including macrocephaly, hypertelorism, sparse eyebrows, broad forehead, prominent nose and pointed chin. The severity of the neurological effects as well as the presence of other features is variable among subjects. SNIBCPS is caused likely by pathogenic and pathogenic variants in CHD3 (Chromodomain Helicase DNA Binding Protein 3), which seems to be involved in chromatin remodeling by deacetylating histones. Here, we report 20 additional patients with clinical features compatible with SNIBCPS from 17 unrelated families with confirmed likely pathogenic/pathogenic variants in CHD3. Patients were analyzed by whole exome sequencing and segregation studies were performed by Sanger sequencing. Patients in this study showed different pathogenic variants affecting several functional domains of the protein. Additionally, none of the variants described here were reported in control population databases, and most computational predictors suggest that they are deleterious. The most common clinical features of the whole cohort of patients are global developmental delay (98%) and speech disorder/delay (92%). Other frequent features (51–74%) include intellectual disability, hypotonia, hypertelorism, abnormality of vision, macrocephaly and prominent forehead, among others. This study expands the number of individuals with confirmed SNIBCPS due to pathogenic or likely pathogenic variants in CHD3. Furthermore, we add evidence of the importance of the application of massive parallel sequencing for NDD patients for whom the clinical diagnosis might be challenging and where deep phenotyping is extremely useful to accurately manage and follow up the patients