Dominant Progressive Hearing Loss
(Source: Boystown Research Registry)
Dominant progressive hearing loss (DPHL) is a form of nonsyndromic genetic deafness. Nonsyndromic means that there are no other medical or physical features that go along with it. The hearing loss in DPHL is sensorineural meaning that it results from impaired functioning of the nerves involved in hearing. This differs from the hearing loss of otosclerosis which involves the bones in the middle ear. As with presbycusis (the hearing loss associated with aging), the hearing loss is progressive, but the age of at which the hearing loss starts is earlier in DPHL.
The age of onset can be in early childhood in some families, but in others the onset may not be noticed until early or middle adulthood. Some people lose the ability to hear high tones or frequencies first, while others may lose the ability to hear the low or middle frequencies first. The onset, rate of progression, initial frequencies involved, and the ultimate severity of the loss vary among families, but are fairly consistent within families.
Some families with DPHL develop balance problems as well as the hearing loss. This type of balance problem, which is referred to as a vestibular dysfunction, results from a change in the semicircular canals. The semi-circular canals are located near the cochlea in the inner ear. Whatever causes the loss of hearing in these individuals, also affects the vestibular function. Other families with DPHL do not have any change in the vestibular system.
Of the various types of genetic hearing loss, DPHL is probably one of the more common.
However, it is not really known how many people have DPHL. Approximately, 20 million people in the United States (8.6% of the population) are considered to be deaf or hearing impaired, but this includes all types of hearing loss at all ages. While various breakdowns of the population are available by severity and age of onset, none address progressive loss. Individuals with DPHL typically would be classified as "hard of hearing" during most of the progression of their loss, although profound deafness may be the end result. Because of the varying age of onset and the changes in their hearing loss over time, individuals with DPHL do not fit easily into broad categories.
DPHL is caused by a single gene that is passed on from generation to generation. Genes carry the code for all the characteristics that we inherit. We have thousands of genes in our 23 pairs of chromosomes. Just as chromosomes come in pairs, so do genes. A dominant gene for hearing loss causes hearing loss even if the other gene in that pair codes for normal hearing. Males and females are equally likely to receive the gene and have the hearing loss. Generally, every person who has a gene for DPHL would be expected to have some hearing loss and each of their children would have a 50% chance of receiving the gene and developing hearing loss.
The variability in the age of onset, the presence or absence of vestibular dysfunction, initial frequencies that are affected, and ultimate severity of hearing loss suggest that more than one gene can cause DPHL, a fact which has been proven by recent genetic studies. In order to better understand the genetics of DPHL, researchers around the world are looking through all of the chromosomes to find the genes for DPHL. The first gene for dominant progressive hearing loss, DFNA1 or Monge´s deafness, was localized to chromosome 5 by Leon et. al. in 1992. The gene was found in a large family in Costa Rica who had a rapidly progressing, adult onset hearing loss which initially involved the low frequencies. The linkage of DPHL to this region has not been reported in any other family and has been excluded in at least 5 families.
A second gene form of DPHL, DFNA3, has been localized to chromosome 1 in an Indonesian family and in an American family by Couke et. al. in 1994. Study of these families will continue until the genes are actually found so that we can learn how the genes cause the hearing loss. By learning how the genes cause the hearing loss, researchers hope to find a way to interfere with that process and prevent the loss.
The following groups can be helpful to individuals and families adapting to progressive hearing loss. The national offices can provide information about groups in your local area.
Association of Late Deafened Adults
10310 Main Street
Fairfax, VA 22030
Self Help for the Hard of Hearing People, Inc.
7910 Woodmont Ave., Suite 1200
Bethesda, MD 20814
Leon, PE., et. al.
(1992) The gene for an inherited form of deafness maps to chromosome 5q31. Proceedings of the National Academy of Science 89: 5181-4.
Coucke, P. et. al
(1994) Linkage of autosomal dominant hearing loss to the short arm of chromosome 1 in two families. New England Journal of Medicine 331: 425-31.
By: Amy Brower
Date Originally Created: Spring of 1995.
The information presented here first appeared in publications of the Boys Town National Research Register for Hereditary Hearing Loss, the National Institute on Deafness and Other Communication Disorders (NIDCD), Hereditary Hearing Impairment Resource Registry (HHIRR), or the Boys Town Research Registry for Hereditary Hearing Loss.
The Boys Town Research Registry for Hereditary Hearing Loss
The Boys Town Research Registry for Hereditary Hearing Loss (Registry) is designed to foster a partnership between families, clinicians and researchers in the area of hereditary hearing loss/deafness through three primary functions. First, the Registry disseminates information to professionals and families about clinical and research issues related to hereditary deafness/hearing loss. Second, the Registry collects information from individuals interested in supporting and participating in research projects. This information is used to support the third function of the Registry - matching families with collaborating research projects.
For more information, contact:
Research Registry for Hereditary Hearing Loss
555 N. 30th Street
Omaha, NE 68131
800 320-1171 (V/TDD)
402 498-6331 (FAX)