Branchiootorenal/branchiootic syndrome

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Branchiootorenal (BOR) syndrome is a condition that disrupts the development of tissues in the neck and causes malformations of the ears and kidneys. The signs and symptoms of this condition vary widely, even among members of the same family. Branchiootic (BO) syndrome includes many of the same features as BOR syndrome, but affected individuals do not have kidney abnormalities. The two conditions are otherwise so similar that researchers often consider them together (BOR/BO syndrome or branchiootorenal spectrum disorders).

"Branchio-" refers to the second branchial arch, which is a structure in the developing embryo that gives rise to tissues in the front and side of the neck. In people with BOR/BO syndrome, abnormal development of the second branchial arch can result in the formation of masses in the neck called branchial cleft cysts. Some affected people have abnormal holes or pits called fistulae in the side of the neck just above the collarbone. Fistulae can form tunnels into the neck, exiting in the mouth near the tonsil. Branchial cleft cysts and fistulae can cause health problems if they become infected, so they are often removed surgically.

"Oto-" and "-otic" refer to the ear; most people with BOR/BO syndrome have hearing loss and other ear abnormalities. The hearing loss can be sensorineural, meaning it is caused by abnormalities in the inner ear; conductive, meaning it results from changes in the small bones in the middle ear; or mixed, meaning it is caused by a combination of inner ear and middle ear abnormalities. Some affected people have tiny holes in the skin or extra bits of tissue just in front of the ear. These are called preauricular pits and preauricular tags, respectively.

"Renal" refers to the kidneys; BOR syndrome (but not BO syndrome) causes abnormalities of kidney structure and function. These abnormalities range from mild to severe and can affect one or both kidneys. In some cases, end-stage renal disease (ESRD) develops later in life. This serious condition occurs when the kidneys become unable to filter fluids and waste products from the body effectively.

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

Mutations in three genes, EYA1, SIX1, and SIX5, have been reported in people with BOR/BO syndrome. About 40 percent of people with this condition have a mutation in the EYA1 gene. SIX1 gene mutations are a much less common cause of the disorder. SIX5 gene mutations have been found in a small number of people with BOR syndrome, although researchers question whether mutations in this gene cause the condition. Some affected individuals originally reported to have SIX5 gene mutations were later found to have EYA1 gene mutations as well, and researchers suspect that the EYA1 gene mutations may be the actual cause of the condition in these people.

The proteins produced from the EYA1, SIX1, and SIX5 genes play important roles in development before birth. The EYA1 protein interacts with several other proteins, including SIX1 and SIX5, to regulate the activity of genes involved in many aspects of embryonic development. Research suggests that these protein interactions are essential for the normal formation of many organs and tissues, including the second branchial arch, ears, and kidneys. Mutations in the EYA1, SIX1, or SIX5 gene may disrupt the proteins' ability to interact with one another and regulate gene activity. The resulting genetic changes affect the development of organs and tissues before birth, which leads to the characteristic features of BOR/BO syndrome.

Some people with BOR/BO syndrome do not have an identified mutation in any of the genes listed above. In these cases, the cause of the condition is unknown.

Inheritance and family implications

From: MedlinePlus Genetics, National Library of Medicine

BOR/BO syndrome is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder. In about 90 percent of cases, an affected person inherits the mutation from one affected parent. The remaining cases result from new mutations in the gene and occur in people with no history of the disorder in their family.

How common is it?

From: MedlinePlus Genetics, National Library of Medicine

Researchers estimate that BOR/BO syndrome affects about 1 in 40,000 people.

Which doctor should you see?

The suggested department for discussing Branchiootorenal/branchiootic syndrome is Nephrology, with a nephrologist as the relevant type of clinician. General physician / Family Medicine; paediatrician for children. Referral depends on symptoms.

Additional services that may be relevant, depending on the findings, include: Clinical Genetics.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• How is kidney function being assessed over time?
• Are any current medicines or supplements relevant to kidney safety?
• Is there an individual recommendation about fluids, diet or blood pressure?

Treatment discussions and follow-up

The material gathered for this draft does not provide a complete condition-specific treatment pathway for Branchiootorenal/branchiootic syndrome. That gap does not mean that treatment is unavailable. A clinician needs to establish the diagnosis and review current guidance before recommending medicines, procedures, rehabilitation or other support.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

The collected references do not establish a complete prevention or long-term outlook section for this entry. Missing information should not be interpreted as proof that prevention is impossible or that a particular outcome is inevitable. Ask what is known for the exact subtype, stage and personal circumstances, and which uncertainties remain.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.