Espectro fenotípico de Síndrome de CHARGE neonatal / Phenotypic spectrum of neonatal CHARGE syndrome

INTRODUCCIÓN: El Síndrome de CHARGE (SCH), es un síndrome genético de amplia variabilidad fenotípica, de he rencia autosómica dominante, causado por variantes patogénicas en el gen CHD7. OBJETIVO: Descri bir el amplio espectro fenotípico de un SCH neonatal, heterocigoto para el gen CDH7 y la utilidad de la secuenciación en la confirmación diagnóstica, considerando los diagnósticos diferenciales. CASO CLÍNICO: recién nacida prematura de 34 semanas, con antecedentes prenatales de polihidroamnios severo, translucencia nucal aumentada y foco hiperecogénico cardiaco, con estudio de TORCH antenatal, que descartó infección congénita. Al nacer se pesquisó parálisis facial periférica, atresia de coanas, dismorfias múltiples, cardiopatía congénita y coloboma retinocoroideo bilateral. Las neuroimágenes mostraron hipoplasia de cóclea y de canales semicirculares bilaterales e hipoplasia pontocerebelosa. Los potenciales evocados auditivos mostraron hipoacusia sensorioneural profunda derecha y anacusia izquierda. Evolucionó con hipocalcemia y alteraciones en la inmunidad, confirmándose un hipoparatiroidismo e hipoplasia de timo. El cariograma fue normal y la amplificación de sondas dependiente de ligandos múltiples (MLPA) excluyó microdeleción 22q11.2. La sospecha clínica de SCH se confirmó con la detección de una variante patogénica en el gen CHD7. CONCLUSIONES: La su perposición de características clínicas del SCH con otros síndromes genéticos requiere confirmación genética molecular considerando diferencias en evolución, terapias y riesgos de recurrencia.

INTRODUCTION: CHARGE syndrome is a genetic disorder of wide phenotypic variability, of autosomal dominant in heritance, caused by pathogenic variants in the CHD7 gene. OBJECTIVE: To describe the broad pheno typic spectrum of neonatal CHARGE syndrome, heterozygous for the CHD7 gene, and the usefulness of genome sequencing in diagnostic confirmation, considering differential diagnoses. CLINICAL CASE: 34-week preterm newborn, with severe prenatal history of polyhydramnios, increased nuchal trans- lucency, and hyperechogenic cardiac focus, with a TORCH study that ruled out congenital infection. Peripheral facial paralysis, choanal atresia, multiple dysmorphisms, congenital heart disease, and bilateral retinochoroidal coloboma were observed at birth. The neuroimaging study showed hypo plasia of the cochlea and bilateral semicircular canals, and pontocerebellar hypoplasia. The auditory evoked potentials showed deep right-sided sensorineural hearing loss and left anacusis. The patient developed hypocalcemia and immunological alterations, confirming hypoparathyroidism and thy mus hypoplasia. The karyogram was normal and 22q11.2 microdeletion was excluded through mul tiplex ligation-dependent probe amplification (MPLA). A pathogenic variant in the CHD7 gene was detected that confirmed the clinical suspicion of CHARGE syndrome. CONCLUSIONS: The overlap of clinical characteristics of CHARGE syndrome requires molecular genetic confirmation, considering differences in evolution, therapies, and recurrence risks with other genetic syndromes.

Non-Homologous End Joining Repair Mechanism-Mediated Deletion of CHD7 Gene in a Patient with Typical CHARGE Syndrome

CHARGE syndrome MIM #214800 is an autosomal dominant syndrome involving multiple congenital malformations. Clinical symptoms include coloboma, heart defects, choanal atresia, retardation of growth or development, genital hypoplasia, and ear anomalies or deafness. Mutations in the chromodomain helicase DNA binding protein 7 (CHD7) gene have been found in 65-70% of CHARGE syndrome patients. Here, we describe a 16-month-old boy with typical CHARGE syndrome, who was referred for CHD7 gene analysis. Sequence analysis and multiplex ligation-dependent probe amplification were performed. A heterozygous 38,304-bp deletion encompassing exon 3 with a 4-bp insertion was identified. There were no Alu sequences adjacent to the breakpoints, and no sequence microhomology was observed at the junction. Therefore, this large deletion may have been mediated by non-homologous end joining. The mechanism of the deletion in the current case differs from the previously suggested mechanisms underlying large deletions or complex genomic rearrangements in the CHD7 gene, and this is the first report of CHD7 deletion by this mechanism worldwide.