Pendred syndrome is a genetic condition impacting hearing, balance, and the thyroid gland. It is characterized by hearing loss that begins early in life, along with the potential development of an enlarged thyroid gland, known as a goiter. The disorder arises from a specific gene mutation that affects the function of the inner ear and thyroid.
Genetic Origins of Pendred Syndrome
Pendred syndrome is caused by mutations in the SLC26A4 gene, which provides instructions for a protein called pendrin. Pendrin functions as a transporter, moving ions across cell membranes. This process is necessary for maintaining the correct fluid balance in the inner ear and for proper thyroid gland function. When the SLC26A4 gene is mutated, the resulting pendrin protein is malformed or nonfunctional, affecting structures for hearing and balance in the inner ear and impairing the thyroid’s ability to process iodide.
Pendred syndrome is inherited in an autosomal recessive pattern. This means a child must inherit two copies of the mutated gene, one from each parent, who are carriers and show no signs of the syndrome.
Key Symptoms and Characteristics
The primary symptom of Pendred syndrome is hearing loss, present at birth or by age three. This hearing impairment is sensorineural, originating from an issue within the inner ear, and is bilateral, affecting both ears. The severity ranges from moderate to profound and often worsens progressively. For some, hearing loss can occur suddenly, sometimes following a minor head injury.
A related anatomical feature is the presence of enlarged vestibular aqueducts (EVA). The vestibular aqueduct is a narrow, bony canal connecting the inner ear to the inside of the skull, and EVA is linked to the risk of sudden hearing decline after head trauma.
The syndrome can also affect the body’s balance system. Because the genetic issue affects the entire inner ear, some individuals experience vestibular weakness, which can manifest as unsteadiness or dizziness.
Another characteristic is the potential development of a goiter, a visible enlargement of the thyroid gland in the neck. A goiter appears later than the hearing loss, often during late childhood or adulthood. While the thyroid gland may function normally despite the enlargement, it can sometimes become underactive (hypothyroidism), causing symptoms like fatigue and weight gain.
The Diagnostic Pathway
The diagnostic process often begins when a newborn fails a hearing screening or a young child shows signs of hearing loss. An audiologist conducts hearing tests to determine the type and severity of the impairment.
Genetic testing provides a definitive diagnosis. A blood sample is analyzed for mutations in the SLC26A4 gene, and finding two mutated copies confirms Pendred syndrome.
Imaging studies are also used. A computed tomography (CT) scan or magnetic resonance imaging (MRI) of the temporal bone can reveal inner ear anomalies, such as enlarged vestibular aqueducts (EVA).
An endocrinologist may assess the thyroid. Blood tests measure hormone levels to check for hypothyroidism, and an ultrasound can evaluate the thyroid’s size and structure if a goiter is present.
Managing Health and Wellbeing
There is no cure for Pendred syndrome, so management focuses on addressing specific symptoms. For hearing loss, early intervention is recommended. Options include:
- Hearing aids for mild to moderate loss.
- Cochlear implants for severe to profound loss.
- Sign language as a communication tool.
Regular thyroid monitoring by an endocrinologist is another component of care. If hypothyroidism develops, it is managed with daily thyroid hormone replacement therapy to restore normal levels.
Lifestyle adjustments are advised to protect remaining hearing. Individuals should avoid contact sports with a high risk of head injury and wear protective headgear during activities like cycling to minimize the risk of sudden hearing loss from trauma. Physical therapy can also help improve stability for those with balance problems.