Usher syndrome (USH) is the most common genetic cause of combined deafness and blindness. It is a rare disease, affecting about 400,000 individuals worldwide and 20,000 to 50,000 individuals in the United States.1,2 While there is no cure for this condition, over a century of scientific discovery has resulted in tremendous advances toward the development of treatments. Despite these advances, less than one percent of people with USH is known to researchers, putting future research and clinical trials at risk. Hearing health care professionals can play a critical role in identifying children and adults with USH.
HISTORY OF USHER SYNDROME
Usher syndrome was first described in 1858 by German ophthalmologist Albrecht von Graefe, who studied three siblings with deafness and progressive vision loss caused by retinitis pigmentosa (RP). In 1914, Scottish ophthalmologist Charles Howard Usher studied 69 families and identified an inherited recessive condition that caused deafness and progressive vision loss in a subset of these families.3 This syndrome was later named after Usher.
The early years of USH research were focused on identifying the different types of Usher syndrome as well as the prevalence and psychosocial aspects. Before genetic testing of this condition became available, children and adults were diagnosed phenotypically based on a history of early-onset hearing loss, progressive vision loss, and the absence or presence of vestibular involvement.
TYPES OF USHER SYNDROME
Three types and nine confirmed genetic subtypes of Usher syndrome have been identified to date (Table 14), distinguished by the severity of hearing loss, age of onset of hearing and vision loss, and the presence or absence of vestibular function.
In 1995, the first causative gene for Usher syndrome was identified. In subsequent years, additional discoveries located genes for five subtypes within USH1, three for USH2, and in 2001, the gene for USH3A.
Historically, a diagnosis of Usher syndrome was devastating, offering few options and resources. Many were told that they would be blind by a certain age, and that the syndrome is so rare they would probably never meet another person with USH. In addition, they had no knowledge of, or access to, researchers around the world who were working to understand Usher syndrome.
IMPORTANCE OF EARLY DIAGNOSIS
Early diagnosis of Usher syndrome is critical so that individuals and families can find support, make informed decisions about communication, and consider options for education, employment, and beyond. However, finding those with USH remains a challenge. The 2017 National Child Count of Children and Youth Who Are Deaf-Blind5 reported only 329 children with Usher syndrome in the United States. This number represents only a fraction of the thousands of children estimated to have USH.6 The Usher Syndrome Coalition maintains the largest international registry of individuals of all ages and types of Usher syndrome, yet that too has less than one percent of the total population registered.
ROLE OF HEARING CARE
Universal newborn hearing screenings have dramatically increased the number of babies identified as deaf or hard of hearing.7 Infants who fail this screening are referred to a hearing health care professional for follow-up. These professionals can play a pivotal role in recognizing the early symptoms of Usher syndrome by understanding its functional impact on a child's development and behavior. These include:
- Type 1: In addition to profound hearing loss, children with Usher type 1 experience vestibular issues that delay the development of their ability to sit upright and walk. Night blindness associated with RP may manifest quite early. Signs of night blindness may include a child appearing to be clumsy or expressing an unusual fear of dimly lit areas. For example, if the audiology booth has low lighting, the child may miss a step or need time for his or her eyes to adjust and get visually oriented to the area.
- Type 2: Children with Usher type 2 experience moderate to severe hearing loss that is often present at birth. The hearing loss is typically milder in the low frequencies and more severe in the higher ones. Children with this condition often use hearing aids and communicate aurally. Functional implications of Usher type 2 may include a perceived loss of hearing, which may actually be related to the impact of progressive vision loss on the ability to speech-read. Also, as vision loss progresses, individuals may pause and visually scan a room before entering.
- Type 3: This is the rarest form of Usher syndrome and the most difficult to diagnose because the vision and hearing loss may not express until the teen years or later. Vestibular dysfunction is variable. This type should be considered as a possible cause of late-onset vision and hearing loss, especially in individuals of Ashkenazi Jewish or Finnish heritage.
More than a century of scientific discovery has resulted in tremendous advances toward the understanding of USH and the development of treatments for this rare genetic disorder. To ensure that treatment development and clinical trials are not delayed, researchers must have access to their greatest resource—people living with Usher syndrome. As the first point of contact, hearing health care professionals can play a critical role in helping to identify infants, children, and adults with this condition. Together, we can help to find, educate, support, and connect the Usher community, one person at a time.
2. Frequency of Usher syndrome in two pediatric populations: Implications for genetic screening of deaf and hard of hearing children. Genetics in medicine : official journal of the American College of Medical Genetics. 2010;12(8):512-6. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3131500/
7. Evaluation of the Universal Newborn Hearing Screening and Intervention Program, PEDIATRICS Volume 126, Supplement 1, August 2010 S www.aappublications.org/news