3: Myopathy Flashcards

1
Q

Define myopathy

A

symmetrical muscle weakness

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2
Q

What are inherited myopathies

A

muscular dystrophies

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3
Q

When does duchenne muscular palsy present

A

5-years

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4
Q

When does Becker muscle dystrophy present

A

10-years, with milder symptoms

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5
Q

What is mcardles disease

A

Autosomal recessive glycogen storage disease that presents with muscle pain following exercise

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6
Q

Describe muscle weakness in myopathies (compared to neuropathies)

A
  • Proximal muscles affected

- Weakness in muscles, wasting is a very late feature

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7
Q

Describe reflexes in myopathies

A

Normal

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8
Q

What is a stereotypical story of a myopathy

A

Person struggles to get out of a chair

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9
Q

What test is raised in myopathy

A

Creatnine kinase

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10
Q

What are the inheritance patterns of myotonic dystrophies

A

Autosomal dominant

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11
Q

How many types of myotonic dystrophies are there

A

2

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12
Q

What chromosome is affected in myotonic dystrophy 1

A

Chromosome 19

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13
Q

What chromosome is affected in myotonic dystrophy 2

A

Chromosome 3

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14
Q

In myotonic dystrophy 1, what feature is present

A

Distal muscle weakness

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15
Q

In myotonic dystrophy 2, what feature is present

A

Proximal muscle weakness

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16
Q

What are features of myotonic dystrophies

A
  • Myotonic facies (long haggard appearance)
  • Frontal balding
  • Bilateral ptosis
  • Cataracts
  • Dysyarthritis
  • Myotonia = tonic muscle spasm
  • Weakness arm and legs
  • DM
  • Testicular atrophy
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17
Q

What is myasthenia gravis

A

Autoimmune condition caused by antibodies raised to postsynaptic acetylcholine receptors

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18
Q

Describe epidemiology of myasthenia gravis

A

Young Females : 20-30 years

Old men: 60-70 years

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19
Q

In women, what age are affected by myasthenia gravis

A

20-30 years

20
Q

In men, what age are affected by myasthenia gravis

A

60-70

21
Q

What causes myasthenia gravis

A

Autoantibodies against acetylcholine receptors on post-synaptic membrane

22
Q

What two conditions is myasthenia gravis associated with

A
  • Thymoma

- Thymic hyperplasia

23
Q

What exacerbates symptoms in myasthenia gravis

A

Exertion

Quinine 
B-blockers 
Penicillamines 
Lithium 
Phenytoin 
Antibiotics
24
Q

Describe diurnal variation in symptoms of myasthenia gravis

A

Symptoms worsen throughout day with repetitive use

25
Q

What muscles are affected first in myasthenia gravis

A

Extra-ocular muscles

26
Q

How do eye symptoms of myasthenia gravis present

A

Ptosis
Diplopia
Blurred vision

27
Q

What does bulbar nerve involvement cause in myasthenia gravis

A

Difficultly swallowing, slurred speech, chewing

28
Q

What muscle weakness is present in myasthenia gravis

A

Proximal muscle weakness

29
Q

How does proximal muscle weakness present

A
  • Difficultly standing from sitting

- Difficultly climbing stairs

30
Q

What is a serious complication of myasthenia gravis

A

Respiratory muscle involvement

31
Q

What are two signs of myasthenia gravis

A

Snarl sign

Peep sign

32
Q

What is snarl sign

A

When patients attempt to smile it appears as a snarl

33
Q

What is peep sign

A

When patient close their eyes. White of sclera is visible

34
Q

What type of hypersensitivity reaction is myasthenia gravis

A

Type 2 (IgG mediated)

35
Q

What is myasthenia crisis

A

Essential muscles - including diaphragm are affected

36
Q

What investigations a performed in myasthenia gravis

A

Repetitive nerve stimulation
AChR antibody testing
EMG
CT thorax - look for thymoma

37
Q

What are two management options added to all patients with myasthenia gravis

A

Pyridostigmine (acetyl choline esterase inhibitor)

Thymectomy - remove gland

38
Q

what is a myasthenia crisis

A

acute life-threatening exacerbation of myasthenia gravis with resp muscle involvement

39
Q

how is myasthenia crisis managed

A

intubation
IVIg
plasmapheresis

40
Q

what is lambort-eaton myasthenic syndrome

A

paraneoplastic syndrome caused by antibodies to pre-synaptic voltage-gated calcium channels

41
Q

what cancer is Lambert-eaton myasthenic syndrome most commonly associated with

A

small cell lung cancer

42
Q

what 3 cancers is lambert-eaton myasthenic syndrome

A

small cell lung cancer
breast
ovarian

43
Q

explain symptoms in Lambert eaton myasthenic syndrome

A
  • repeated muscle contraction leads to increase in strength.
  • Limb girdle weakness
  • Hyper-reflexia

Autonomic symptoms:

  • Dry mouth
  • ED
  • Difficultly micturating
44
Q

what investigation is ordered for Lambert eaton myasthenic syndrome

A

repetitive nerve stimulation

45
Q

how is lamber eaton myasthenic syndrome managed

A
  • treat cancer

- immunosuppressants (prednisolone, azathioprine)