In developed countries like the United States, four out of every 100,000 babies are born with an inherited condition called Usher syndrome. Symptoms include hearing loss or deafness, a vision disorder called retinitis pigmentosa (RP) and problems with balance.
Hearing health professionals believe Usher syndrome is responsible for three to six percent of all childhood deafness and 50 percent of deafness and blindness in adults. Because it is a recessive genetic disorder, children must receive the same mutated gene from each parent in order to inherit the syndrome. When both parents are carriers of the same mutated gene, they have a one-in-four chance of having a child with Usher syndrome.
Scientists have identified three types of the disorder, all with varying degrees of severity. Children born with Type 1 Usher syndrome are profoundly deaf at birth and have severe balance problems. They are typically slow to sit, often don’t walk on their own before 18 months of age and develop vision problems before the age of 10.
Because children born with Type 2 Usher syndrome have moderate to severe hearing loss, they typically don’t experience the same balance problems as those with Type 1. Vision problems tend to develop more slowly and they are also better candidates for hearing aids.
Children born with Type 3 Usher syndrome have normal hearing at birth and near normal balance. Their vision and hearing deteriorate gradually, with most individuals requiring hearing aids as teenagers or young adults and becoming legally blind by mid-adulthood.
Since Usher syndrome involves hearing, vision and balance, physicians evaluate all three senses to reach a diagnosis. Typically, hearing is tested with an audiogram, an electroretinogram (ERG) evaluates vision, and an electronystagmogram (ENG) measures involuntary eye movements that may indicate a problem with balance. Other tests may also be ordered depending upon the patient’s symptoms and medical history.
Although Usher syndrome isn’t currently curable, scientists Michelle Hastings of Chicago Medical School and Jennifer Lentz of the Louisiana State University Health Science Center have recently partly restored hearing to young mice with an injection containing a laboratory-created fragment of RNA designed to interfere with the effects of the faulty gene. The National Institutes of Health have given the scientists a $1.3 million grant for four more years of studies to perfect the effects and timing of the shots to improve or treat the hearing loss.
Usher syndrome isn’t curable; however healthcare professionals agree that early identification is instrumental in understanding and managing the disorder. Some children benefit from hearing aids or cochlear implants while others, depending upon the characteristics of their disorder, may benefit from enrolling in special education classes to learn sign language and how to read Braille.