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Pendred Syndrome
Wednesday, 17 November 2004
Wednesday, 17 November 2004
Goiter-deafness syndrome, Thyroid hormone organification defect IIb

What

Pendred Syndrome is a rare, inherited, genetic disorder characterized by hearing loss from birth and malformations of the bony parts of the ears. In addition, the thyroid gland in the neck (near the Adam’s apple) is often enlarged.

Who

Pendred syndrome occurs in both males and females, and in all ethnicities. Although the actual incidence of Pendred syndrome is not known, it is estimated to occur in about 1/10,000 to 1/100,000 live births. Pendred syndrome is also thought to account for about 5-10% of congenital hearing loss. This means that for every 100 people with congenital hearing loss, 5-10 of them may have Pendred syndrome. Pendred syndrome is an autosomal recessive type of genetic disorder. This means that the parents both have at least one altered copy of the gene causing the syndrome, and that affected child inherited two altered copies of the gene, one from each parent. Individuals with one altered copy and one normal copy do not have the disease or its symptoms, but are called “carriers”, since the altered copy can be passed on genetically to children. In a family with unaffected parents and an affected child, children of any other pregnancies have a one in four chance of inheriting the disease.

Signs and Symptoms

Individuals with Pendred Syndrome generally have congenital hearing loss, which means that there is hearing loss from birth. In some individuals, the hearing loss may occur later during infancy and childhood. The hearing loss is often severe, but can be mild to moderate in some cases. There may also be abnormalities in the formation or the structure of the ears. The ear is normally comprised of 3 parts: an outer, middle, and inner part. Pendred syndrome usually causes abnormalities in the bony part of the inner ear, which includes a bone called the temporal bone. A part of the ear called the vestibular aqueduct may also be wider then normal, which can affect the body’s balance. In addition, another part of the ear called the cochlea may not grow normally (cochlear hypoplasia). The cochlea is also important for normal hearing and balance. In some individuals, Pendred syndrome can cause the thyroid gland in the neck to become larger then normal, which is called thyroid goiter. This enlargement can occur during late childhood, adolescence, or as an adult. The thyroid gland normally produces a hormone called thyroxine by utilizing iodine in the body. Pendred syndrome disrupts thyroxine production by blocking iodine utilization. The thyroid gland may attempt to compensate for the loss of thyroxine by becoming enlarged (goiter).

Possible Causes

Genetic disorders are often caused by mutations in specific genes. Individuals with Pendred syndrome may have a mutation in a gene called SLC26A4 (or PDS for short). This gene is on chromosome 7 and normally helps form a protein called pendrin. This protein may help transport iodine to the thyroid cells to help make thyroid hormone. Other genes are likely involved in Pendred syndrome, but they have not yet been identified.

Diagnosis

Pendred syndrome is diagnosed based on the presence of clinical features, such as congenital hearing loss and the abnormalities of the bony parts of the ear. Screening for hearing loss is recommended for newborns and at least within the first month of life. Hearing loss can be formally tested in infants and young children using different methods by an audiologist. Imaging studies such as CT scans (computed tomography) are often performed to evaluate for bony abnormalities of the ears. The presence of goiter (enlarged thyroid gland) is also highly suggestive of the syndrome. A special test, called the perchorlate discharge test, can also be done to check whether the thyroid gland is working properly. In addition, blood tests can be done to check the levels of thyroid hormone in the blood.

Treatment

Although there is no cure for Pendred syndrome, a team of doctors can help treat the signs and symptoms of Pendred syndrome. This team will likely include the child’s regular physician, a geneticist, an audiologist, and an endocrinologist. The audiologist can help find out how much hearing loss there is, and can recommend hearing aids to help with hearing. If the hearing loss is very severe, a device called a cochlear implant may be used. Since hearing loss often affects speech and language development, other educational programs for hearing loss and early speech therapy may be helpful. The endocrinologist can help treat problems with the thyroid gland.

Prognosis

Individuals with Pendred syndrome generally have a good prognosis with a normal lifespan.

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

These 3 websites provide short summaries of the features found in Pendred syndrome.

http://ghr.nlm.nih.gov/condition=pendredsyndrome http://www.cafamily.org.uk/Direct/p165.html

http://www.medicinenet.com/Pendred_Syndrome/article.htm

National Institute on Deafness and other Communication Disorders
In a Q&A format, this website goes over many questions that may help you, and has a list of additional links that may be useful.

American Society for Deaf Children
Phone: 800-942-2732 (parent hotline)  This website has educational and networking resources for families and children affected by hearing loss. Under the “snapshots” section, you can brochures on different topics, like cochlear implants. They also have a support group website listed below. (http://groups.yahoo.com/group/asdc_deafchildren )

National Association of the Deaf
Phone: 301-587-1788  Under the “Info Center” link, you can find answers to common questions that people have about hearing loss, its impacts, and educational and job opportunities. They also have a group for members.

National Parent to Parent Network
This network provides support groups for families with rare diseases. Since pendred syndrome has not yet been listed, you can form a new group or contact families affected with similar syndromes.

Google Search for Pendred Syndrome

References and Sources

www.geneclinics.org/profiles/pendred/ www.medterms.com/script/main/art.asp?articlekey=9049 www.ghr.nlm.nih.gov/condition=pendredsyndrome www.genome.gov/10000666 www.geneclinics.org/servlet/access?id=8888890&key=E7lpwcE2apY9v&gry=INSERTGRY&fcn=y&fw=JDLC&filename=/glossary/profiles/deafness-overview/index.html www.orpha.net/consor/cgi-bin/OC_Exp.php?Lng=GB&Expert=705 www.ibis-birthdefects.org/start/pendreds.htm www.ncbi.nlm.nih.gov/books/bv.fcgi?call=bv.View..ShowSection&rid=gnd.section.125