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Hearing And Balance > Genetic Causes of Hearing Loss > Flashcards

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
Q

What might be required for airway obstruction in severe Treacher-Collins syndrome?

A

Tracheostomy

26
Q

Why are siblings of patients with Treacher-Collins syndrome at a higher risk of having the condition themselves?

A

There is a risk of gonadal mosaicism in an unaffected parent

27
Q

What are the features of Waardenburg syndrome?

A
  • Pigmentary anomalies of hair, skin, or eyes

- Hearing loss

28
Q

What is the inheritance pattern of Waardenburg syndrome?

A

Can be autosomal dominant or autosomal recessive

29
Q

What are the features of CHARGE syndrome?

A
  • Coloboma
  • Heart defects
  • Atresia of chonae
  • Retarded growth and development
  • Genital hypoplasia
  • Ear anomalies
30
Q

What ear abnormalities can be seen in CHARGE syndrome?

A
  • Absent semi circular canals

- VIII’th nerve hypoplasia

31
Q

What is the inheritance pattern of CHARGE syndrome?

A

Autosomal dominant

32
Q

How severe is CHARGE syndrome?

A

Clinical features are highly variable

33
Q

How severe is the intellectual impairment in CHARGE syndrome?

A

Can vary from mild to profound

34
Q

What aspects of development may appear delayed in CHARGE syndrome?

A
  • Speech delay

- Gross motor delay

35
Q

Why might a child have speech delay in CHARGE syndrome?

A

Secondary to deafness

36
Q

Why might a child have gross motor delay in CHARGE syndrome?

A

Due to absent vestibular function

37
Q

What are the features of Alport syndrome?

A
  • High frequency sensorineural hearing loss

- Nephritis

38
Q

What is the inheritance pattern of Alport syndrome?

A

X-linked, autosomal recessive, or autosomal dominant

39
Q

How does Alport syndrome present?

A

Intermittent haematuria (microscopic at first) leading to renal failure

40
Q

How is Alport syndrome diagnosed?

A

Characteristic findings on renal biopsy

41
Q

What should be considered when a child is diagnosed with non-syndromic hearing loss?

A

Hearing loss associated with syndromes often is the first presenting feature, so may be incorrected diagnosed as non-syndromic

42
Q

Why is it important to correctly diagnose syndrome hearing loss?

A
  • Monitor for complications

- For the purposes of genetic counselling

43
Q

What does hearing loss at birth suggest?

A

In the absence of a proven environmental factor, most hearing loss at birth is likely to be genetic

44
Q

When does hearing loss at birth have a high rate of recurrence?

A

An isolated case of congenital hearing loss, especially if severe or profound

45
Q

Why does an isolated case of congenital hearing loss at birth have a high risk of recurrence?

A

Because it is most likely to be autosomal recessive

46
Q

What is the first step in assessing hearing loss at birth?

A

Detailed history and examination

47
Q

What is the next investigation if it is not thought that hearing loss at birth is syndromic after history and examination?

A

Genetic testing

48
Q

Which gene in particular is it important to analyse in non-syndromic hearing loss at birth?

A

GJB2 gene

49
Q

What is the mode of inheritance of non-syndromic hearing loss?

A

May follow any mode of inheritance

50
Q

What is the most common mode of inheritance of non-syndromic hearing loss?

A

Autosomal recessive

51
Q

What % of cases of genetic hearing loss are autosomal recessive?

A

80%

52
Q

What is the implication of most cases of non-syndromic hearing loss being autosomal recessive?

A

There may be no family history of deafness, but risk of recurrence

53
Q

What is the risk of recurrence in autosomal recessive non-syndromic hearing loss?

A

1 in 4

54
Q

What % of cases of non-syndromic hearing loss are autosomal dominant?

A

10-15%

55
Q

What % of cases of non-syndromic hearing loss are X-linked or mitochondrially inherited?

A

5%

Hearing And Balance (2 decks)

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