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Branchiootorenal syndrome 2(BOR2)

MedGen UID:
Concept ID:
Disease or Syndrome
Synonym: BOR2
Gene (location): SIX5 (19q13.32)
Monarch Initiative: MONDO:0012575
OMIM®: 610896

Disease characteristics

Excerpted from the GeneReview: Branchiootorenal Spectrum Disorder
Branchiootorenal spectrum disorder (BORSD) is characterized by malformations of the outer, middle, and inner ear associated with conductive, sensorineural, or mixed hearing impairment, branchial fistulae and cysts, and renal malformations ranging from mild renal hypoplasia to bilateral renal agenesis. Some individuals progress to end-stage renal disease (ESRD) later in life. Extreme variability can be observed in the presence, severity, and type of branchial arch, otologic, audiologic, and renal abnormality from right side to left side in an affected individual and also among individuals in the same family. [from GeneReviews]
Richard JH Smith   view full author information

Additional description

From MedlinePlus Genetics
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.  https://medlineplus.gov/genetics/condition/branchiootorenal-branchiootic-syndrome

Clinical features

From HPO
Renal insufficiency
MedGen UID:
Concept ID:
Disease or Syndrome
A reduction in the level of performance of the kidneys in areas of function comprising the concentration of urine, removal of wastes, the maintenance of electrolyte balance, homeostasis of blood pressure, and calcium metabolism.
Renal dysplasia
MedGen UID:
Concept ID:
Congenital Abnormality
The presence of developmental dysplasia of the kidney.
Hearing impairment
MedGen UID:
Concept ID:
Disease or Syndrome
A decreased magnitude of the sensory perception of sound.
Hemifacial hypoplasia
MedGen UID:
Concept ID:
Disease or Syndrome
Unilateral underdevelopment of the facial tissues, including muscles and bones.
Preauricular skin tag
MedGen UID:
Concept ID:
A rudimentary tag of skin often containing ear tissue including a core of cartilage and located just anterior to the auricle (outer part of the ear).

Term Hierarchy

CClinical test,  RResearch test,  OOMIM,  GGeneReviews,  VClinVar  

Professional guidelines


Masuda M, Kanno A, Nara K, Mutai H, Morisada N, Iijima K, Morimoto N, Nakano A, Sugiuchi T, Okamoto Y, Masuda S, Katsunuma S, Ogawa K, Matsunaga T
Sci Rep 2022 Jan 19;12(1):969. doi: 10.1038/s41598-022-04885-w. PMID: 35046468Free PMC Article
Unzaki A, Morisada N, Nozu K, Ye MJ, Ito S, Matsunaga T, Ishikura K, Ina S, Nagatani K, Okamoto T, Inaba Y, Ito N, Igarashi T, Kanda S, Ito K, Omune K, Iwaki T, Ueno K, Yahata M, Ohtsuka Y, Nishi E, Takahashi N, Ishikawa T, Goto S, Okamoto N, Iijima K
J Hum Genet 2018 May;63(5):647-656. Epub 2018 Mar 2 doi: 10.1038/s10038-018-0429-8. PMID: 29500469
Milunsky JM, Maher TM, Zhao G, Wang Z, Mulliken JB, Chitayat D, Clemens M, Stalker HJ, Bauer M, Burch M, Chénier S, Cunningham ML, Drack AV, Janssens S, Karlea A, Klatt R, Kini U, Klein O, Lachmeijer AM, Megarbane A, Mendelsohn NJ, Meschino WS, Mortier GR, Parkash S, Ray CR, Roberts A, Roberts A, Reardon W, Schnur RE, Smith R, Splitt M, Tezcan K, Whiteford ML, Wong DA, Zori R, Lin AE
Am J Med Genet A 2011 Jan;155A(1):22-32. doi: 10.1002/ajmg.a.33783. PMID: 21204207

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