Pendred syndrome is a rare genetic disorder that causes early hearing loss in children. It affects multiple body systems and is present from birth or develops in early childhood. The syndrome is named after Vaughan Pendred, the physician who first described individuals with the disorder in 1896. This condition is one of the more common forms of syndromic genetic deafness, potentially accounting for 7.5% to 15% of congenital hearing loss cases.
Key Features of Pendred Syndrome
Individuals with Pendred syndrome experience hearing loss, often by age three. This hearing impairment is sensorineural, involving problems with the inner ear’s hearing structures, and often affects both ears. The severity of hearing loss varies, ranging from mild to profound, and it commonly worsens over time, sometimes leading to total deafness. Fluctuations in hearing ability are also common.
Another feature of Pendred syndrome is the development of a goiter, an enlargement of the thyroid gland. While a goiter may be present in the first decade of life, it becomes more common by the end of the second decade. Despite the presence of a goiter, thyroid hormone levels in affected individuals are often normal, though mild hypothyroidism (underactive thyroid) can occur.
The syndrome is also linked to a specific inner ear malformation known as Mondini dysplasia. This involves an abnormal partitioning of the cochlea, which may have a reduced number of turns. Additionally, a dilated endolymphatic duct and sac with a widened vestibular aqueduct are commonly observed. These inner ear anomalies can contribute to balance issues, with many patients experiencing such problems.
The Genetic Cause
Pendred syndrome results from mutations within the SLC26A4 gene, which is located on chromosome 7. The SLC26A4 gene provides instructions for making a protein called pendrin.
Pendrin plays a role in transporting ions, which is important for the proper function of the inner ear and the thyroid gland. When mutations occur in the SLC26A4 gene, the production or function of pendrin is disrupted, leading to the symptoms of Pendred syndrome.
The inheritance pattern for Pendred syndrome is autosomal recessive. This means that an individual must inherit two copies of the mutated SLC26A4 gene, one from each parent, to develop the condition. Parents who carry one copy of the mutated gene are unaffected themselves but can pass the gene to their children.
Diagnosis and Management Strategies
Diagnosing Pendred syndrome involves identifying its characteristic features. Genetic testing for SLC26A4 gene mutations confirms the diagnosis. Imaging studies of the inner ear, such as CT or MRI scans, detect specific malformations like Mondini dysplasia and a widened vestibular aqueduct. Thyroid function tests also assess thyroid activity and identify hypothyroidism.
While there is currently no cure for Pendred syndrome, management focuses on addressing symptoms and improving the quality of life. Hearing interventions are a primary component of care, often including hearing aids to amplify sound. For those with more profound hearing loss, cochlear implants can be considered. Learning sign language may also be beneficial for communication as hearing loss progresses.
Thyroid function is regularly monitored, and if hypothyroidism develops, hormone replacement therapy may be prescribed to maintain thyroid hormone levels. A multidisciplinary team approach, involving audiologists, endocrinologists, and other specialists, provides comprehensive care. This coordinated effort helps manage hearing, thyroid health, and any balance issues.