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Genetic Causes of Hearing Loss Flashcards

1
Q

Is genetically determined hearing loss isolated or syndromic?

A

Can be either

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2
Q

What is meant by syndromic hearing loss?

A

Hearing loss associated with other abnormal clinical features

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3
Q

What % of genetically determined childhood-onset hearing loss is non-syndromic?

A

70%

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4
Q

How many genes are known to underlie non-syndromic hearing loss?

A

Over 100

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5
Q

How many syndromes that have hearing loss as a feature have been described?

A

Over 600

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6
Q

Give 7 syndromes in which hearing loss is a major feature?

A
  • Usher
  • Jervell and Lange-Nielsen
  • Pendred
  • Treacher Collins
  • Waardenburg
  • CHARGE
  • Alport
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7
Q

What are the features of Usher syndrome?

A
  • Hearing loss

- Retinal dystrophy

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8
Q

How does Usher syndrome initially present?

A

NSHL

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9
Q

What should be monitored for in Usher syndrome?

A

Visual impairment

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10
Q

What are the features of Jervell and Lange-Nielsen syndrome?

A
  • Congenital profound hearing loss with absent vestibular function
  • Long QT interval with possible syncope
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11
Q

What is the inheritance pattern of Jervell and Lange-Nielsen syndrome?

A

Autosomal recessive

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12
Q

How does Jervell and Lange-Nielsen syndrome initially present?

A

NSHL

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13
Q

What should be assessed in Jervell and Lange-Nielsen syndrome?

A

QT interval

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14
Q

How are QT abnormalities in Jervell and Lange-Nielsen syndrome treated?

A

Beta blockers or ICD (depending on cardiologists advice)

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15
Q

Why is detection of Jervell and Lange-Nielsen syndrome important?

A

Mortality is high if untreated

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16
Q

What are the features of Pendred syndrome?

A
  • Progressive high frequency hearing loss
  • Thyroid dyshormonogenesis
  • Enlarged vestibular aqueducts and incomplete partitioning of the cochlea
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17
Q

What is vestibular function like in Pendred syndrome?

A

It may be normal or affected

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18
Q

What is the inheritance pattern of Pendred syndrome?

A

Autosomal recessive

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19
Q

How does Pendred syndrome initially present?

A

NSHL

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20
Q

What should be assessed for in Pendred syndrome?

A
  • Goitre
  • Dyshormogenesis
  • Subsequent hypothyroidism
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21
Q

What are the features of Treacher Collins syndrome?

A
  • Bilateral, symmetrical facial features
  • Abnormal external ears often with meatal atresia
  • Cleft palate
  • Malar, zygomatic, and mandibular hypoplasia
  • Coloboma of lower eyelids and sparse lower eyelashes
  • Ossicular abnormalities
  • Sensorineural hearing loss
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22
Q

What is the inheritance pattern of Treacher Collins syndrome?

A

Autosomal dominant

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23
Q

How serious is Treacher Collins syndrome?

A

It can range from mild to severe

24
Q

What can complicate severe cases of Treacher Collins syndrome?

A

Airway obstruction

25
What might be required for airway obstruction in severe Treacher-Collins syndrome?
Tracheostomy
26
Why are siblings of patients with Treacher-Collins syndrome at a higher risk of having the condition themselves?
There is a risk of gonadal mosaicism in an unaffected parent
27
What are the features of Waardenburg syndrome?
- Pigmentary anomalies of hair, skin, or eyes | - Hearing loss
28
What is the inheritance pattern of Waardenburg syndrome?
Can be autosomal dominant or autosomal recessive
29
What are the features of CHARGE syndrome?
- Coloboma - Heart defects - Atresia of chonae - Retarded growth and development - Genital hypoplasia - Ear anomalies
30
What ear abnormalities can be seen in CHARGE syndrome?
- Absent semi circular canals | - VIII'th nerve hypoplasia
31
What is the inheritance pattern of CHARGE syndrome?
Autosomal dominant
32
How severe is CHARGE syndrome?
Clinical features are highly variable
33
How severe is the intellectual impairment in CHARGE syndrome?
Can vary from mild to profound
34
What aspects of development may appear delayed in CHARGE syndrome?
- Speech delay | - Gross motor delay
35
Why might a child have speech delay in CHARGE syndrome?
Secondary to deafness
36
Why might a child have gross motor delay in CHARGE syndrome?
Due to absent vestibular function
37
What are the features of Alport syndrome?
- High frequency sensorineural hearing loss | - Nephritis
38
What is the inheritance pattern of Alport syndrome?
X-linked, autosomal recessive, or autosomal dominant
39
How does Alport syndrome present?
Intermittent haematuria (microscopic at first) leading to renal failure
40
How is Alport syndrome diagnosed?
Characteristic findings on renal biopsy
41
What should be considered when a child is diagnosed with non-syndromic hearing loss?
Hearing loss associated with syndromes often is the first presenting feature, so may be incorrected diagnosed as non-syndromic
42
Why is it important to correctly diagnose syndrome hearing loss?
- Monitor for complications | - For the purposes of genetic counselling
43
What does hearing loss at birth suggest?
In the absence of a proven environmental factor, most hearing loss at birth is likely to be genetic
44
When does hearing loss at birth have a high rate of recurrence?
An isolated case of congenital hearing loss, especially if severe or profound
45
Why does an isolated case of congenital hearing loss at birth have a high risk of recurrence?
Because it is most likely to be autosomal recessive
46
What is the first step in assessing hearing loss at birth?
Detailed history and examination
47
What is the next investigation if it is not thought that hearing loss at birth is syndromic after history and examination?
Genetic testing
48
Which gene in particular is it important to analyse in non-syndromic hearing loss at birth?
GJB2 gene
49
What is the mode of inheritance of non-syndromic hearing loss?
May follow any mode of inheritance
50
What is the most common mode of inheritance of non-syndromic hearing loss?
Autosomal recessive
51
What % of cases of genetic hearing loss are autosomal recessive?
80%
52
What is the implication of most cases of non-syndromic hearing loss being autosomal recessive?
There may be no family history of deafness, but risk of recurrence
53
What is the risk of recurrence in autosomal recessive non-syndromic hearing loss?
1 in 4
54
What % of cases of non-syndromic hearing loss are autosomal dominant?
10-15%
55
What % of cases of non-syndromic hearing loss are X-linked or mitochondrially inherited?
5%

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