Definition of Pendred syndrome

Pendred syndrome: A genetic disease characterized by congenital deafness, abnormality of the bony labyrinth in the inner ear, and goiter (enlargement of the thyroid gland). The congenital nerve deafness is severe to profound and is not progressive (does not get worse). The abnormality of the labyrinth is evident on a CT scan of the temporal bone in the skull. The goiter is not present at birth but develops in early puberty or adulthood. It is due to a defect in the making of thyroid hormone (thyroid hormone organification defect). However, there is usually a normal level of thyroid hormone (euthyroid) due to compensated hypothyroidism. Other key features of the syndrome include defects in vestibular function, malformation of the balance portion of the ear (the cochlea), swelling in front of neck due to the goiter, and mental retardation due to the congenital thyroid defect. Pendred syndrome is inherited in an autosomal recessive manner and is due to mutation in the SLC26A4 gene on chromosome 7q31 that encodes a protein called pendrin. Also known as deafness with goiter, goiter-deafness syndrome, and thyroid hormone organification defect IIb.

More information: Pendred syndrome (PDS) is the hereditary association of congenital deafness (deafness at the time of birth) and goiter (enlargement of the thyroid gland in the front of the neck) due to a defect in the making of thyroid hormone. The features of Pendred syndrome in outline are as follows:

• Inner ear: Congenital neurosensory (nerve) deafness; defect in vestibular function; and malformation of the balance portion of the ear (cochlea);
• Hormonal: Seemingly normal level of thyroid hormones (euthyroid) due to compensated hypothyroidism;
• Neck: Goitrous swelling in front of neck;
• Intelligence: Mental retardation (due to congenital thyroid defect);
• Oncology : Possible increased risk of thyroid carcinoma (thyroid carcinoma);
• Laboratory : Evidence for defect in the making of thyroid hormone (thyroid hormone organification defect); and
• Inheritance: Autosomal recessive with both seemingly normal parents carrying a copy of the Pendred syndrome (PDS) gene and each of their children having a 1 in 4 (25%) risk of inheriting both parental PDS genes and suffering from the syndrome.

Pendred syndrome was clinically recognized and concisely described in 1896 by the English general practitioner Vaughan Pendred (1869-1946). Exactly a century later, the gene for Pendred syndrome was discovered (by Coyle and Sheffield and colleagues) to be on chromosome 7q.

Pendred syndrome is also known as deafness with goiter, the goiter-deafness syndrome, and now (thanks to molecular medicine) thyroid hormone organification defect IIb.