Branchiootorenal syndrome Health Article

Definition

Branchiootorenal (BOR) syndrome is an autosomal dominant condition characterized by ear abnormalities, hearing loss, cysts in the neck, and kidney problems.

Description

The name branciootorenal syndrome describes the body systems most commonly affected by this genetic disorder. The term "branchio" refers to the abnormalities of the neck found in individuals with this syndrome. Cysts (lump or swelling that can be filled with fluid) and fistulas (abnormal passage from the throat to the skin) in the neck occur frequently. The term "oto" refers to the ear disorders associated with the syndrome. For example, the outer ear can be unusual in appearance. Hearing loss is also common. Finally, the term "renal" stands for the kidney problems commonly seen in patients with this condition. These can be very mild or very severe, as can any of the symptoms associated with this disorder.

Dr. M. Melnick first described branchiootorenal (BOR) syndrome in 1975. Another name for BOR syndrome is Melnick-Fraser syndrome. Individuals with BOR syndrome typically have physical differences that are present at birth (congenital). These birth defects are caused by a change (mutation) in a gene.

Genetic profile

Scientists recently discovered that mutations in the EYA1 gene cause BOR syndrome. The EYA1 gene is located on chromosome 8. The exact function of the EYA1 gene is unknown, but mutations in this gene disrupt normal development, producing the physical differences common to BOR syndrome. A mutation in this gene can affect the normal development of the ear, kidney, and the branchial arches. The branchial arches are tissues that develop very early in pregnancy and are involved in the formation of the face and neck.

BOR syndrome is inherited in a dominant manner. This means that only one gene in the pair must be mutated in order for the individual to be affected. If a person has a mutation in one of their EYA1 genes, the disorder is typically present. The characteristics of the syndrome can be extremely variable in severity.

A mutation in the EYA1 gene may be inherited from a parent with BOR syndrome. A mutation can also occur by chance, in an individual without a family history of BOR syndrome. If a child inherits an abnormal gene from a parent, the signs of the disorder can be very different between the parent and the child. This is called variable expressivity. For example, a parent who has a very mild form of BOR syndrome can have a severely affected child. The reverse situation can also occur.

Once an individual has a mutation in the EYA1 gene, there is a 50/50 chance with each pregnancy that the gene will be passed on. This means that there is a 50/50 chance of having a child with BOR syndrome. Male and female children have the same risk. It does not matter if the gene is inherited from the mother or the father.

Demographics

BOR syndrome occurs in one of every 40,000 live births. BOR syndrome is seen in all ethnic groups and cultures. It also affects males and females equally. One study suggested that 2% of individuals with severe hearing loss have BOR syndrome.

Signs and symptoms

The characteristics associated with BOR syndrome are highly variable. Some individuals with BOR syndrome have many physical deformations. Other individuals with BOR syndrome have a few minor physical differences. The birth defects can occur on only one side of the face (unilateral) or be present on both sides (bilateral).

Abnormal development of the ears is the most common characteristic of BOR syndrome. The ears may be smaller than normal (microtia) and may have an unusual shape. Ear tags (excess pieces of skin) may be seen on the cheek next to the ear. Preauricular pits (small pits in the skin on the outside of the ear) are found in 75% of patients with BOR syndrome. Hearing loss is present in 85% of individuals with BOR syndrome and this loss may be mild or severe.

The most distinctive finding in individuals with BOR syndrome is the presence of cysts or fistulas in the neck region due to abnormal development of the branchial arches. These cysts and fistulas can be filled with or discharge fluid.

Approximately two-thirds of individuals with BOR syndrome also have kidney abnormalities. These abnormalities can be very mild and cause no health problems, or they can be very severe and life threatening. The kidneys can be smaller than normal (renal hypoplasia), abnormally shaped, malfunctioning, or totally absent (renal agenesis).

Other less common characteristics associated with BOR syndrome include cleft palate, facial nerve paralysis, and abnormalities of the tear ducts. The tear ducts (lacrimal ducts) may be absent or abnormal. Some patients with BOR syndrome uncontrollably develop tears while chewing (gustatory lacrimation).