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Townes-Brocks Syndrome
Wednesday, 09 March 2005
Wednesday, 09 March 2005
Renal-Ear-Anal-Radial (REAR) Syndrome

What

Townes-Brocks syndrome is a very rare, hereditary disorder characterized by multiple malformations. It is also sometimes referred to as renal-ear-anal-radial (REAR) syndrome. The main abnormalities affect the ears (structure and hearing function), hands, anus, and kidneys. Most patients with this syndrome have normal intelligence, although mental retardation has been seen in a few affected people.

Who

This disorder occurs in both males and females, and 65 cases worldwide were published between its description in 1972 and 1999. It is usually inherited from a parent, but the diagnosed person can also be the first and only member of the family to have the condition. In the latter case, the person is said to have a new mutation or break in the specific gene associated with this condition. When inherited, it is transmitted in an autosomal dominant fashion. This means that a parent with the condition passes on the broken gene carrying the disorder to 50% of his or her children. If the child gets the broken gene, he or she will have the syndrome, although the severity is variable from person to person, even within the same family. Parents have no control over whether or not they pass on the broken gene, and it is no one’s fault.

Signs and Symptoms

Many of the features of the syndrome are easily recognized. Ear structure abnormalities include small size, abnormal folding, cupped appearance, or presence of skin tags or pits. Hand structure abnormalities include extra fingers (polydactyly), split fingers (bifurcation), fingers that are not separated (syndactyly), or hands that curve to the side (ulnar deviation). Foot structure abnormalities include short or overlapping toes, toes with syndactyly, and small or absent third toe. Anal anomalies include lack of an anal opening (imperforate anus). This is often associated with an abnormal connection between the intestines and the vagina or urethra (rectovaginal or rectourethral fistulae). In these situations, stool mixes with urine or is passed from the vagina. Other anal anomalies include a tight anal opening (anal stenosis), abnormal position where the anus is too close to the genitals (anteriorly placed), and excessive skin around the anus. Male patients with this syndrome may also have a skin line extending from the genitals to the rectum (midline perineal raphe), a scrotum that is split into two halves (bifid), and an abnormally placed urinary opening of the penis (hypospadias). Language development problems and behavior difficulties are the main signs of hearing loss. A wide variety of symptoms can occur if the kidneys are involved, including fluid retention, lack of making urine, and poor growth. Other abnormalities that may be rarely associated with this syndrome are mental retardation and heart defects (difficulty feeding, breathing problems, blue lips and skin, and poor growth).

Possible Causes

The condition is caused by abnormalities in a gene named SALL1, located on chromosome 16. This gene is important for normal development of the organs affected by the syndrome.

Diagnosis

The diagnosis is suggested by the presence of two or more of the following: 1) anal abnormalities (imperforate anus, anteriorly placed anus, anal stenosis), 2) hand abnormalities (polydactyly, bifid thumb, thumb with an extra bone and joint termed a triphalangeal thumb), 3) external ear abnormalities (small size, “lop” ear, skin pits or tags), 4) a relative with the syndrome. Hearing defects are generally diagnosed by newborn hearing screen, or later, by hearing tests. A special imaging study called a CT scan can diagnose inner ear abnormalities contributing to hearing loss. Kidney and urinary tract problems are diagnosed and monitored by blood, urine, and imaging tests. Heart abnormalities can be detected by clinical examination and echocardiography (an ultrasound of the heart). Genetic testing to look for the specific, abnormal gene can be done to further assist in making the diagnosis. Prenatal diagnosis may be possible by chorionic villus sampling or amniocentesis if a fetus is known to be at risk.

Treatment

The treatment is primarily surgical to correct the malformations of the anus, hands, feet, and ears. Some urinary tract abnormalities can also be surgically repaired. Genital abnormalities can often be surgically corrected, and it is important that male children with this syndrome not be circumcised at birth so that the foreskin can be used for reconstruction. Heart defects can generally be surgically corrected. Hearing loss may be managed with hearing aids, or surgically with a cochlear implant. These children may benefit from learning sign language, depending on their degree of hearing loss. If serious kidney problems are present, dialysis may be necessary to replace the normal kidney functions while awaiting a kidney transplant.

Prognosis

The prognosis is generally very good for these children. Those with mental retardation may need special education assistance, in addition to assisted living as adults. Those with hearing loss can generally adapt very well to this disability and still live full lives. The serious problems for children with this syndrome relate to the potential heart and kidney defects, which could lead to a shortened life span. However, there are many treatment options to support patients in these circumstances.

Connect with other parents

In the spirit of community and support, Madisons Foundation offers the unique service of connecting parents of children with rare diseases. If you would like to be connected to other parents of children with this disease, please fill out this brief form.

Weblinks

Alexander Graham Bell Association for the Deaf and Hard of Hearing:
A useful resource and support system to promote successful living with hearing loss. Provides many publications, conferences, extensive information and resources.

American Society for Deaf Children:
A parent-helping-parent organization which provides information, encouragement, and support for families of deaf or hard of hearing children. Sponsors conventions and fundraisers. One year free membership for families of newly diagnosed deaf or hard of hearing children. Many links to other organizations for those with hearing loss. Provides valuable information regarding important issues like sign language use with babies, cochlear implants, communication, and suggested reading for parents.

International Center for Disease Support community for people affected by Townes-Brocks Syndrome:
An online chat group to connect people with this syndrome.

Google Search for Townes-Brocks Syndrome

References and Sources

Gene Reviews: www.geneclinics.org OMIM: www.ncbi.nlm.nih.gov Doray, B; Langer, B; Stoll, C (1999): Two cases of Townes-Brocks syndrome. Genet. Counsel. 10: 359-367 Kohlhase, J (2000): SALL1 Mutations in Townes-Brocks Syndrome and Related Disorders. Hum. Mutat. 16(6): 460-466 Kohlhase, J, et al (1999): Molecular Analysis of SALL1 Mutations in Townes-Brocks Syndrome. Am. J. Hum. Genet. 64:435-445 . Malhotra, P (2004): Townes-Brocks Syndrome. Indian Pediatrics. 41:743. Powell, CM; Michaelis RC (1999): Townes-Brocks Syndrome. J. Med. Genet. 36:89-93