Pendred syndrome

Pendred syndrome is a disorder typically associated with hearing loss and a thyroid condition called goiter. A goiter is an enlargement of the thyroid gland, which is a butterfly-shaped organ at the base of the neck that produces hormones. If a goiter develops in a person with Pendred syndrome, it usually forms between late childhood and early adulthood. In most cases, this enlargement does not cause the thyroid gland to malfunction.

In most people with Pendred syndrome, severe to profound hearing loss caused by changes in the inner ear (sensorineural hearing loss) is evident at birth. In other cases, hearing loss does not develop until later in infancy or early childhood.

Other abnormalities of the inner ear are also common in Pendred syndrome. Some affected individuals have problems with balance caused by dysfunction of the part of the inner ear that helps maintain the body's balance and orientation (the vestibular system). Additionally, a structure called the vestibular aqueduct is unusually large in people with Pendred syndrome. The vestibular aqueduct is a bony canal that connects the inner ear with the brain cavity. An enlarged vestibular aqueduct (EVA) is a characteristic feature of Pendred syndrome, but it is not the cause of hearing loss in people with this condition.

Pendred syndrome is a common form of syndromic deafness (hearing loss that occurs with signs and symptoms affecting other parts of the body). This condition likely accounts for about 10 percent of all hereditary hearing loss. The exact incidence of Pendred syndrome is unknown.

Mutations in the SLC26A4 gene cause about half of all familial cases of Pendred syndrome. The SLC26A4 gene provides instructions for making a protein called pendrin. This protein transports negatively charged particles (ions), including chloride, iodide, and bicarbonate, into and out of cells. Although the function of pendrin is not fully understood, this protein is important for the normal functions of the thyroid and inner ear. Mutations in the SLC26A4 gene alter the structure or function of pendrin, which disrupts ion transport. Impaired pendrin activity in the thyroid and inner ear is responsible for the characteristic signs and symptoms of Pendred syndrome.

In some cases, the cause of Pendred syndrome is unknown. Researchers are looking for additional genetic changes that may underlie the condition.

Read more about the SLC26A4 gene.

This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.