Branchio-oto-renal (BOR) syndrome is a rare disorder inherited as an autosomal dominant genetic trait. This disorder is characterized by pits or ear tags in front of the outer ear, abnormal passages from the throat to the outside surface of the neck (branchial fistulas), branchial cysts, hearing loss and/or kidney (renal) abnormalities.
Most people with branchio-oto-renal syndrome have some type of hearing loss. The hearing loss may be due to nerve damage (sensory), blockage of sound waves (conductive), or both. The degree of hearing loss varies from mild to profound, and can differ between the two ears. The deafness can be stable or progressive. Other abnormalities related to the ear may be: pits or outgrowths of cartilage (tags) in front of the outer ear; a cupped or small outer ear; and/or a narrow or upward slanted outer ear canal.
An abnormal passage from the throat to the outside surface of the neck (branchial fistula), and/or an opening, cyst, or mass in the tonsil area is often present.
Many people with branchio-oto-renal syndrome do not experience kidney problems. Among those who do, the abnormalities range from mild to very severe. In milder cases, the kidney may be unusually shaped. In more severe cases, there may be duplication of the collecting system of the kidneys and/or absence or failure of one or both of the kidneys to form.
Other abnormalities that have been found in association with branchio-oto-renal syndrome are: narrowing of the tear duct in the eyes interfering with the normal flow of tears; a long narrow face; cleft palate; paralysis of certain muscles in the face; and/or a deep overbite.
Branchio-oto-renal syndrome is inherited through an autosomal dominant disorder. Dominant genetic disorders occur when only a single copy of an abnormal gene is necessary for the appearance of the disease. The abnormal gene can be inherited from either parent, or can be the result of a new mutation (gene change) in the affected individual. The risk of passing the abnormal gene from affected parent to offspring is 50% for each pregnancy regardless of the sex of the resulting child.
The BOR gene is located on the long arm of chromosome 8 (8q13.3). Chromosomes, which are present in the nucleus of human cells, carry the genetic information for each individual. Human body cells normally have 46 chromosomes. Pairs of human chromosomes are numbered from 1 through 22 and the sex chromosomes are designated X and Y. Males have one X and one Y chromosome and females have two X chromosomes. Each chromosome has a short arm designated “p” and a long arm designated “q”. Chromosomes are further sub-divided into many bands that are numbered. For example, “chromosome 8q13.3” refers to the area between bands 13 and 14 on the long arm of chromosome 8. The numbered bands specify the location of the thousands of genes that are present on each chromosome.
Genetic diseases are determined by the combination of genes for a particular trait that are on the chromosomes received from the father and the mother.
Branchio-oto-renal syndrome affects males and females in equal numbers. It is estimated that 1 in 40,000 people are afflicted with this disorder. BOR syndrome is found in approximately 2 to 3 percent of children with profound deafness.
The diagnosis is made when at least two of five features (branchial defects, hearing loss, pits or tags in front of the outer ear (preauricular pits), abnormalities of the part of the ear that projects from the head (pinna), and renal malformations) are present in an individual with two or more affected family members, or three features are present in an individual with no affected family members.
Evaluation of hearing function (audiologic assessment), and imaging (CT or computerized tomography) of the temporal bone to identify the middle and inner ear defects, should be performed. Renal abnormality (anomaly) is investigated by urinalysis, renal function tests, and imaging studies such as renal ultrasonography and CT.
The child with hearing impairment should undergo appropriate rehabilitation measures with annual hearing testing (audiometry). Medical attention should be sought promptly for any episode of inflammation of the middle ear (otitis media).
Patients with branchio-oto-renal syndrome may benefit from hearing aids. When structural defects of the ear are present, surgery may be beneficial.
Branchial cleft deformities have the potential to become easily infected and may require surgical treatment. Also, a physician specializing in kidney problems (nephrologist) should closely monitor any renal impairment. Surgical repair may be undertaken for correctable defects. Severe kidney problems may warrant dialysis or kidney transplantation.
Genetic counseling may be of benefit for patients and their families. Other treatment is symptomatic and supportive.
Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government website.
For information about clinical trials being conducted at the National Institutes of Health (NIH) Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:
Tollfree: (800) 411-1222
TTY: (866) 411-1010
For information about clinical trials sponsored by private sources, contact:
The National Institute on Deafness and Other Communication Disorders (NIDCD) of the National Institutes of Health is sponsoring a study involving clinical and genetic analysis of inner ear malformations. This study will try to identify and understand the genetic factors that may lead to inner ear malformations that cause hearing loss. For information, contact the NIH Patient Recruitment and Public Liaison Office at (800) 411-1222 or email@example.com (TTY: 866-411-1010).
Boys Town National Research Hospital in Omaha, NB, maintains a Research Registry for Hereditary Hearing Loss. For information about current studies, visit that institution’s Web site at www.boystownhospital.org or call (800) 835-1468 (voice or TDD).
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FROM THE INTERNET
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