For most people who have a child with Bilateral Renal Agenesis (BRA - no kidneys), it is a "fluke," a one-time occurrence that the doctors cannot explain. However, for some people, it is the result of a genetic disorder
and can happen again in subsequent children.  One of the known genetic disorders that can cause BRA is a syndrome known as BOR.  According to recent studies, BOR is believed to occur in 1 in 40,000 people. It is estimated that 2% of the profoundly deaf have BOR.

Taken from the BOR Research Project pamphlet put out by Boys Town National Research Hospital, Omaha, Nebraska, USA:

What is BOR?

BOR (Branchio-OTO-Renal) is a dominant genetic condition which can result in hearing loss, ear pits, branchial (neck) cysts or fistulas, and kidney anomalies. Individuals with BOR ususally do not have all of these symptoms, thus BOR is said to have variable expression. And although these are the most common symptoms, many others have been reported but are not common.

About 90% of BOR patients have a hearing loss. The hearing loss found in BOR is highly variable. The loss can be sensorineural, conductive or mixed.  It can be stable or progressive and the severity can range from mild to profound.

Ear pits are found in abour 80% of the BOR cases. An ear pit is a small hole immediately in front of the top of the ear. Of those persons with ear pits, some have only one while others have one in front of each ear. Some individuals have deformed outer-ear(s), middle-ear(s), and/or inner-ear(s).

About 60% of the BOR cases have branchial cysts or fistulas which are small holes located on the front, external lower third of the neck. Some of these open into the throat and may drain fluid from time to time. People with branchial cycts or fistualas usually have two (one on each side); however, some only have one. Because they often become infected, branchial cysts or
fistulas are often surgically removed.

Kidney anomalies are found in about 15% of those with BOR. Most of the anomalies have minimal clinical significance and consists of minor changes in the anatomy of the kidney or urine collection system.  Kidney function is normal in these individuals.  Because these persons have no clinical reason to view the kidney/urine collection system, these changes may be
more common than we think.  More severe kidney anomalies have been reported. These range from small, normal functioning kidneys all the way to the kidneys (one or both) being absent.

Three of the less common symptoms associated with BOR are ear tags (which look somewhat like a mole and are found immediately in front of the ear), blocked tear ducts (causing tearing because the fluid around the eye cannot drain normally), and short palate.

What Causes BOR?

BOR is a dominant genetic condition. Genes are found on the chromosomes in the nucleus of each cell. Chromosomes come in pairs (there are two chromosome number "1s", "2s", etc.) and humans have 23 pairs of chromosomes. Each of us received 23 chromosomes  (one of each pair) from each parent. Since chromosomes come in pairs, genes also come in pairs.  Genes carry the necessary information to cause a single cell, the fertilized egg, to grow into an adult human being.  Geneticists estimate
that each of us probably have several genes which do not function properly.  The scientists call this a mutation (a change in the genetic material).  Usually these mutations do not cause problems because the other gene of the
pair performs the intended function. However, in dominant genetic conditions it takes only one mutated gene to cause the syndrome.

BOR is caused by the EYA1 gene on chromosome 8.  When the family tree of a family with BOR is constructed, you will usually find the syndrome in every generation.  When  a person with BOR has children, each child has a 1 in 2 chance of receiving the gene which causes BOR.

Genetic Research on BOR

The genetics laboratory at Boys Town National Research Hospital was one of the first to determine there is a gene on chromosome 8 which causes BOR.  The gene was identified by a laboratory in France. Now that the gene has been identified, it can be studied.  The results of this study may reveal how the mutation causes BOR and why these is such a wide variation of symptoms among individuals with BOR.  With this understanding it may be possible, in the future, to develop treatments for this condition.

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