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Pendred syndrome is an autosomal recessive genetic disorder characterized by:

1. Bilateral sensorineural hearing loss (SNHL)
2. Enlarged vestibular aqueduct (EVA) and/or inner ear malformations (e.g., Mondini malformation)
3. Thyroid dysfunction, usually presenting as goiter (with or without hypothyroidism) </aside>

It is one of the most common syndromic forms of congenital deafness.

Pathophysiology

• Gene involved: SLC26A4 (PDS) located on chromosome 7q31
• Encodes pendrin, an anion transporter involved in:
  • Iodide transport in the thyroid
  • Bicarbonate/chloride exchange in the inner ear and kidney
• Defective pendrin leads to:
  • Abnormal endolymphatic fluid homeostasis → EVA and SNHL
  • Impaired iodide organification → dyshormonogenetic goiter

Clinical Features

Ear and Hearing

• Congenital or early-onset bilateral SNHL
• Typically progressive and fluctuating
• May have sudden hearing loss after minor head trauma or barotrauma
• Hearing loss is often severe to profound
• Associated inner ear malformations:
  • EVA (most common)
  • Incomplete partition type II (Mondini deformity)

Thyroid

• Goiter (usually develops in late childhood or adolescence)
• May have euthyroid or hypothyroid function
• Rarely leads to overt hypothyroidism in childhood
• Positive perchlorate discharge test (iodide organification defect)