Deaf Blindness - Usher Syndrome
I discovered it is a relatively rare genetic disorder but the most common cause of deaf blindness. I had never heard of it so I did a little reading. Usher syndrome, named for the researcher who first isolated the genes, is caused when both the mother and father carry a defective gene, but even then there is only a 1 in 4 chance that the offspring will have it. There is also a 50% chance, that even if they don’t the children don’t have Usher syndrome they will be carriers which means it can be passed on to subsequent generations.
Usher syndrome is most often the result of consanguinity – that is two people closely related, having children. Both parents must have the abnormal gene for the syndrome to occur. If only one parent has the defective gene the syndrome does not occur but they themselves could be a carrier. Interestingly there are some clusters of the syndrome – one of them is Usher III in Birmingham Alabama (where my daughter lives!) and Finland. Usher’s only happens in about 0.01% of the population in the USA, however the incidence is double that in Germany and slightly less than the USA in Norway.
There are three types of Usher’s Syndrome. All syndromes involve deafness but not everyone will develop blindness. While there are varying degrees and time frames to develop symptoms, of the three types Usher’s 1 is the worst. The child is deaf at birth and loses their vision over the next 10 years. Usher’s II the child is hard of hearing at birth, which usually remains stable, and loses their vision later. Usher’s III the person usually become deaf by adulthood and develop blindness later in life.
Ushers syndrome is, at present incurable although gene therapy does look promising. The hearing loss is sensorineural and this can be ‘treated’ with a Cochlear implant. People with Usher who have received a Cochlear Implant find they get similar results to those of us who were deafened due to some other cause. This is a great benefit because it allows them to continue to communicate with the people around them.
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