"The children involved in the study were born with DFNB9, which accounts for between 2 and 8% of hereditary deafness. It is caused by mutations in the OTOF gene which prevent the production of functioning otoferlin protein, which can significantly reduce sound transmission from the inner ear hair cells to hearing nerves."

Just shows how much of our body functions we take for granted. Every function has a critical path that is so vulnerable. This is despite the human body having all kinds of redundancies. Our body is so resilient, yet at times, some of the mechanisms are so fragile.