Zdeněk Čada1, Dana Šafka Brožková2, Zuzana Balatková3, Pavlína Plevová4, Dagmar Rašková5, Jana Laštůvková6, Rudolf Černý7, Veronika Bandúrová3, Vladimír Koucký3, Silvie Hrubá3, Martin Komarc8, Ján Jenčík2, Simona Poisson Marková2, Jan Plzák3, Jan Kluh3, Pavel Seeman2. 1. Department of Otorhinolaryngology and Head and Neck Surgery, 1st Faculty of Medicine, Charles University, Faculty Hospital Motol, Postgraduate Medical School, V Úvalu 84, Praha 5, 15006, Prague, Czech Republic. zdenek.cada@fnmotol.cz. 2. DNA Laboratory, Department of Paediatric Neurology, 2nd Faculty of Medicine, Charles University and Motol University Hospital, Prague, Czech Republic. 3. Department of Otorhinolaryngology and Head and Neck Surgery, 1st Faculty of Medicine, Charles University, Faculty Hospital Motol, Postgraduate Medical School, V Úvalu 84, Praha 5, 15006, Prague, Czech Republic. 4. Department of Medical Genetics, University Hospital Ostrava, Ostrava, Czech Republic. 5. Centre for Medical Genetics and Reproductive Medicine, Gennet, Prague, Czech Republic. 6. Department of Medical Genetics, Masaryk Hospital, Regional Health Corporation, Ústí nad Labem, Czech Republic. 7. Department of Neurology, 2nd Faculty of Medicine, Charles University and Motol University Hospital, Prague, Czech Republic. 8. Department of Anthropomotorics and Methodology, Faculty of Physical Education and Sport, Charles University, Prague, Czech Republic.
Abstract
INTRODUCTION: Hearing loss is the most frequent sensory disorder and is genetically extremely heterogeneous. By far the most frequent cause of nonsyndromic autosomal recessive hearing loss (AR-NSHL) are biallelic pathogenic mutations in the GJB2 gene causing DFNB1. The worldwide search for the second most common type of AR-NSHL took almost two decades. Recently reported alterations (mostly deletions) of the STRC gene, also named DFNB16, seem to be the second most frequent cause of AR-NSHL. Genetic testing of STRC is very challenging due to the highly homologous pseudogene. Anecdotal evidence from single patients shows that STRC mutations have their typical audiological findings and patients usually have moderate hearing loss. The aim of this study is to discover if audiological findings in patients with biallelic pathogenic mutations affecting STRC have the characteristic features and shape of audiological curves and if there are genotype/phenotype correlations in relation to various types of STRC mutations. METHODS: Eleven hearing loss patients with pathogenic mutations on both alleles of the STRC gene were detected during routine genetic examination of AR-NSHL patients. Audiological examination consisted of pure tone audiometry, stapedial reflexes, tympanometry and otoacoustic emission tests. RESULTS: The threshold of pure tone average (PTA) was 46 dB and otoacoustic emissions were not detectable in these DFNB16 patients. All patients were without vestibular irritation or asymmetry. CONCLUSION: Moderate sensorineural hearing loss is typical for DFNB16-associated hearing loss and there are no significant differences in audiological phenotypes among different types of mutations affecting STRC.
INTRODUCTION:Hearing loss is the most frequent sensory disorder and is genetically extremely heterogeneous. By far the most frequent cause of nonsyndromic autosomal recessive hearing loss (AR-NSHL) are biallelic pathogenic mutations in the GJB2 gene causing DFNB1. The worldwide search for the second most common type of AR-NSHL took almost two decades. Recently reported alterations (mostly deletions) of the STRC gene, also named DFNB16, seem to be the second most frequent cause of AR-NSHL. Genetic testing of STRC is very challenging due to the highly homologous pseudogene. Anecdotal evidence from single patients shows that STRC mutations have their typical audiological findings and patients usually have moderate hearing loss. The aim of this study is to discover if audiological findings in patients with biallelic pathogenic mutations affecting STRC have the characteristic features and shape of audiological curves and if there are genotype/phenotype correlations in relation to various types of STRC mutations. METHODS: Eleven hearing losspatients with pathogenic mutations on both alleles of the STRC gene were detected during routine genetic examination of AR-NSHL patients. Audiological examination consisted of pure tone audiometry, stapedial reflexes, tympanometry and otoacoustic emission tests. RESULTS: The threshold of pure tone average (PTA) was 46 dB and otoacoustic emissions were not detectable in these DFNB16patients. All patients were without vestibular irritation or asymmetry. CONCLUSION: Moderate sensorineural hearing loss is typical for DFNB16-associated hearing loss and there are no significant differences in audiological phenotypes among different types of mutations affecting STRC.
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