## **Core Concept**
Pendred syndrome is a genetic disorder leading to congenital bilateral sensorineural hearing loss, often associated with thyroid abnormalities. It is caused by mutations in the SLC26A4 gene, which encodes for pendrin, a protein crucial for iodide transport in the thyroid and for maintaining endolymphatic pH in the inner ear. This condition accounts for a significant proportion of hereditary hearing loss cases.

## **Why the Correct Answer is Right**
Pendred syndrome is characterized by bilateral sensorineural hearing loss, goiter (enlargement of the thyroid gland), and often, thyroid dysfunction. The SLC26A4 gene mutation affects the function of pendrin, leading to impaired iodide organification in the thyroid and altered ion transport in the inner ear. This results in the clinical manifestations of Pendred syndrome, making option **C** the correct answer due to its relevance to the syndrome's pathophysiology and clinical presentation.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because while Pendred syndrome does involve hearing loss, the specificity and combination of symptoms such as goiter and hearing loss make it more detailed than a simple hearing loss description.
- **Option B:** This option is incorrect as it does not accurately reflect the primary characteristics of Pendred syndrome, which include both hearing loss and thyroid gland abnormalities.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl for Pendred syndrome is that patients often have a positive perchlorate discharge test, indicating impaired iodide organification in the thyroid. This is a critical diagnostic clue. Additionally, imaging studies like the computed tomography (CT) scan may show inner ear abnormalities, such as enlarged vestibular aqueducts, which are highly suggestive of Pendred syndrome.

## **Correct Answer:** .