(RxWiki News) People who have inherited a form of hearing loss appear to have inherited an increased sensitivity in their sense of touch as well, establishing a genetic link between the two senses.
The genetic mutation that causes DFNA2 hearing loss, a form of progressive deafness, also allows a person with the condition to feel low frequency vibrations that are typically too slow for healthy people to perceive.
"An unusual symptom may sometimes be linked to a seemingly unrelated condition."
Authors Thomas Jentsch and Gary Lewin of the Max Delbrück Center for Molecular Medicine Berlin-Buch in Germany worked with researchers in Spain and the Netherlands to test families whose members have DFNA2.
A series of touch experiments revealed a connection between the two senses that the scientists suspected existed when they discovered that a protein molecule existed both in the ear and on the sensory cells of the skin.
The protein molecule, called KCNQ4, plays a part in the way vibrations detected by the fine, tiny hairs in the inner ear are transmitted to the brain through electric signals.
But the genetic mutation that causes DFNA2 hearing loss destroys KCNQ4. When the scientists found KCNQ4 in skin cells as well, they thought the same genetic mutation might affect people's sense of touch as well.
People with this form of hearing loss, usually detected in childhood, cannot hear higher frequency sounds as well as those without the mutation. As they age, the condition worsens until they begin to lose hearing in moderate and lower frequencies as well.
Just as sound is comprised of vibrations in the air, humans' sense of touch is defined by the vibrations that occur on the skin when it touches different textures and surfaces.
The discovery of a genetic mutation that affects both hearing loss and a person's sense of touch helps scientists better understand the connections between different symptoms in patients.
The clinical study appeared in Nature Neuroscience online in November.