Pesquisa audiológica y molecular para pérdida auditiva por mutación 35delG en el gen de la conexina 26 e infección congénita por citomegalovirus / Audiologic and molecular screening for hearing loss by 35delG mutation in connexin 26 gene and congenital cytomegalovirus infection

Las pérdidas auditivas pueden ser atribuidas a factores genéticos o ambientales. Las mutaciones en el gen de la proteína Cx26 (conexina 26) son responsables de un 30-80% de los casos de pérdida auditiva profunda no sindrómica. La variante 35delG es la prevalente en la población caucásica. Entre los factores ambientales, el citomegalovirus (CMV) es la principal causa de infección congénita. Objetivos. Determinar la prevalencia de infección congénita por CMV y la frecuencia de la mutación 35delG en recién nacidos. Identifcar aquellos con riesgo de pérdida de audición con el fn de realizar un seguimiento audiológico para detectar precozmente las hipoacusias. Material y métodos. Se analizaron 1020 muestras de sangre seca, en papel, de recién nacidos, por PCR convencional y en tiempo real. Se efectuaron las otoemisiones acústicas antes del alta hospitalaria a todos los niños. El seguimiento audiológico se realizó tanto a los portadores de 35delG como a los que tuvieron infección congénita por CMV. Resultados. De los pacientes estudiados, 15 fueron heterocigotas para la mutación 35delG. No se detectaron homocigotas. Seis de las muestras fueron positivas para CMV (resultados confirmados en orina); de ellos, solo un neonato fue sintomático. A todos estos niños se les realizaron las evaluaciones audiológicas; presentaron hipoacusia tres niños con infección congénita por CMV y dos portadores de la mutación 35delG. Conclusión. Se detectó un 1,3% de portadores de la mutación 35delG y una frecuencia de infección congénita por CMV del 0,6%. El seguimiento audiológico de estas dos poblaciones permitió la detección de hipoacusias tardías.

Introduction. Hearing loss may be attributed to genetic and environmental factors. Mutations in the gene of the CX26 protein (connexin 26), are responsible for 30-80% of all cases of non-syndromic profound hearing loss. The 35delG is the most frequent variant in the caucasian population. As to environmental factors, the cytomegalovirus (CMV) is the main cause of congenital infection. Objetives. To determine the prevalence of congenital CMV infection and the frequency of the 35delG mutation in newborns. To identify those at risk of suffering hearing loss in order to do an audiologic follow-up of detected cases. Materials y methods. One thousand and twenty samples of dry blood spots corresponding to newborns were tested using conventional and real time PCR. Audiologic screening was performed to all newborns before hospital discharge. Results. Fifteen out of 1020 subjects were heterozygous for the mutation. No homozygous patients were found. Six out of the samples tested positive for CMV (confrmed by a urine sample), out of which only one newborn was symptomatic. The auditory brainstem response was recorded in all these children. Hearing loss was found in three children with congenital CMV infection and two with 35delG mutation. Conclusion. The frecuency of 35delG mutation carriers in our population was 1.3% and the CMV congenital infection prevalence was 0.6%. Audiologic monitoring of these two populations allowed detection of hearing loss of late onset.

[Audiologic and molecular screening for hearing loss by 35delG mutation in connexin 26 gene and congenital cytomegalovirus infection]. / Pesquisa audiológica y molecular para pérdida auditiva por mutación 35delG en el gen de la conexina 26 e infección congénita por citomegalovirus.

INTRODUCTION: Hearing loss may be attributed to genetic and environmental factors. Mutations in the gene of the CX26 protein (connexin 26), are responsible for 30-80% of all cases of non-syndromic profound hearing loss. The 35delG is the most frequent variant in the caucasian population. As to environmental factors, the cytomegalovirus (CMV) is the main cause of congenital infection. OBJECTIVES: To determine the prevalence of congenital CMV infection and the frequency of the 35delG mutation in newborns. To identify those at risk of suffering hearing loss in order to do an audiologic follow-up of detected cases. MATERIALS AND METHODS: One thousand and twenty samples of dry blood spots corresponding to newborns were tested using conventional and real time PCR. Audiologic screening was performed to all newborns before hospital discharge. RESULTS: Fifteen out of 1020 subjects were heterozygous for the mutation. No homozygous patients were found. Six out of the samples tested positive for CMV (confirmed by a urine sample), out of which only one newborn was symptomatic. The auditory brainstem response was recorded in all these children. Hearing loss was found in three children with congenital CMV infection and two with 35delG mutation. CONCLUSION: The frecuency of 35delG mutation carriers in our population was 1.3% and the CMV congenital infection prevalence was 0.6%. Audiologic monitoring of these two populations allowed detection of hearing loss of late onset.