✅ Model Answer:
• Diagnosis: Pendred syndrome (SLC26A4 mutation) — enlarged vestibular aqueduct (EVA), Mondini malformation on CT, goiter with positive perchlorate discharge test, progressive fluctuating SNHL. Mother with hearing loss suggests autosomal recessive inheritance.
• Any other test: Positive Perchlorate discharge test, Genetic testing for SLC26A4 mutations, thyroid ultrasound, renal function (associated anomalies), ophthalmology exam, audiometry (already done).
• What to do next: Avoid contact sports (risk of hearing fluctuation/drop). Hearing aids if needed. Monitor hearing closely (serial audiometry). Consider cochlear implant if severe-progressive.
• Follow-up plan: Serial audiometry every 6 months (can drop suddenly). Endocrine follow-up for goiter (thyroid function). Genetic counseling. Avoid aminoglycosides and head trauma.

✅ Model Answer:
• Pendred syndrome is an autosomal recessive disorder caused by mutations in the SLC26A4 gene (encodes pendrin protein).
• Classic triad:
- Sensorineural hearing loss: Usually bilateral, progressive, can be fluctuating (may worsen with minor head trauma)
- Enlarged vestibular aqueduct (EVA): Found on CT temporal bone (most common inner ear anomaly)
- Goiter: Euthyroid goiter (thyroid enlargement with normal function) — due to organification defect
• Other features:
- Mondini malformation (incomplete partition of the cochlea)
- Positive perchlorate discharge test
- Associated with vestibular dysfunction (dizziness, imbalance)

✅ Model Answer:
• SLC26A4 gene: Located on chromosome 7q31, encodes pendrin — a chloride-iodide transporter protein.
• Function:
- In the inner ear: Pendrin transports chloride and bicarbonate in the endolymphatic sac → maintains fluid homeostasis and endolymph volume. Mutation leads to EVA and SNHL.
- In the thyroid: Pendrin transports iodide into the thyroid colloid → essential for thyroid hormone synthesis. Mutation leads to organification defect → goiter.
• Inheritance: Autosomal recessive.
• Mutations: More than 200 mutations identified (frameshift, missense, splice-site).

✅ Model Answer:
• Perchlorate discharge test: A test used to detect thyroid organification defects.
• Procedure:
- Radioactive iodine (¹²³I or ¹³¹I) is given orally.
- Baseline thyroid uptake measured (usually 1 hour).
- Potassium perchlorate is given (blocks further iodine uptake).
- Measurement: Thyroid uptake is measured again 1 hour later.
• Interpretation:
- Positive: If radioactive iodine is discharged (>10-15% drop) — indicates inability to organify iodide (pendrin dysfunction).
- Negative: Normal organification.
• In Pendred syndrome: Usually positive (thyroid cannot trap and organify iodide efficiently).
• Clinical significance: Helps distinguish Pendred from other causes of goiter with hearing loss.

✅ Model Answer:
• Type: Sensorineural hearing loss (SNHL) — usually bilateral, symmetric.
• Severity: Variable — can range from mild to profound.
• Progression: Progressive — hearing can worsen over time (usually first 2-3 decades).
• Fluctuation: Fluctuating — hearing may vary with minor head trauma, barotrauma, or even spontaneously.
• Onset: Usually congenital or early childhood (often diagnosed by age 4-10 years).
• Key feature: Sudden hearing drops — can occur after minor head injury (e.g., falls, sports).
• Imaging: CT temporal bone shows Enlarged Vestibular Aqueduct (EVA) (most common) ± Mondini malformation.
• Management: Hearing aids initially; cochlear implants if severe-progressive.

✅ Model Answer:
• Avoid contact sports:
- Football, soccer, basketball, wrestling, boxing (risk of head trauma)
- Head trauma (even minor) can cause sudden hearing deterioration in EVA
• Activities to avoid:
- Scuba diving, sky diving (pressure changes)
- Activities with rapid acceleration/deceleration (e.g., roller coasters)
- Hyperbaric oxygen therapy (if needed, consult ENT)
• Allowed activities:
- Swimming (with ear protection if needed), running, cycling (with helmet), non-contact sports
• Rationale: Enlarged vestibular aqueduct (EVA) is associated with increased risk of hearing loss from minor trauma due to changes in CSF or endolymph pressure.
• Counseling: Educate parents and child about activity restrictions and emergency plan if hearing drops suddenly.

✅ Model Answer:
• Complications:
- Progressive hearing loss: May lead to severe-profound SNHL (need for cochlear implant)
- Sudden hearing drops: After minor head trauma (can be irreversible)
- Vestibular dysfunction: Dizziness, vertigo, imbalance (due to EVA and inner ear anomalies)
- Goiter: Usually euthyroid, but can become hypothyroid (5-10% of cases)
- Thyroid disease: May develop hypothyroidism or thyroid nodules (rare)
- Mondini malformation: Associated with increased risk of meningitis (CSF leak)
- Speech/language delay: If hearing loss is not managed early
- Psychological: Anxiety about hearing fluctuations, social/emotional impact

✅ Model Answer:
• Prognosis:
- Variable: Depends on severity of hearing loss and progression
- Hearing: May progress to severe-profound (30-40% require cochlear implant)
- Thyroid: Usually euthyroid (goiter) but may develop hypothyroidism later
- Life expectancy: Normal (non-life-threatening)
• Long-term management:
- Audiology: Serial audiometry every 6 months (monitor for sudden drops)
- ENT: Regular ear exams, discuss cochlear implant candidacy if needed
- Endocrinology: Annual thyroid function, goiter monitoring
- Activity restrictions: Avoid contact sports, head trauma
- Genetic counseling: Autosomal recessive (25% recurrence risk for siblings)
- Hearing aids/CI: Early intervention to optimize speech and language
- Emergency plan: If sudden hearing loss occurs → immediate audiogram + ENT consult (steroids if new-onset SNHL)