Hearing loss with copy number variation: A case series

Abstract

Hereditary deafness accounts for 50– 60% of congenital deafness cases, and > 100 genetic mutations have been identified. Most are deletions, insertions, and single nucleotide variation. In recent years, copy number variations (CNVs) have also been recognized to cause hearing loss. Herein, we report three cases of hearing loss caused by CNV.

Case 1 was of an 8-year-old girl with mild sensorineural hearing loss. Hearing loss was identified at wellness checkups during her elementary school years. Genetic testing identified homozygous long deletion in the STRC gene. Case 2 was of an 11-year-old girl with moderate sensorineural hearing loss. Her hearing loss was identified before she commenced elementary school. Genetic testing detected homozygous long deletion in the OTOA gene. Case 3 was of a 10 year-old-girl, who is the sister of the girl in Case 2. She had undergone neonatal hearing screening, and moderate sensorineural hearing loss was detected with same genetic variants as those of her sister in Case 2.

STRC and OTOA genes are frequently detected genes in hearing loss cases caused by CNV. Depending on the range of deletion of CNV, it may also affect the flanking sequence. During genetic counseling, it is necessary to consider whether the contiguous gene syndrome can be diagnosed based on phenotypes and genetic testing results.