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AIP: Acute weakness > Severe myositis > Flashcards

Severe myositis Flashcards

1
Q

What happens to muscle bulk and reflexes in polymyositis?

A

they are preserved until very late

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2
Q

What is polymyositis?

A

inflammatory disorder causing symmetrical, proximal muscle weakness

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3
Q

What is thought to be the cause of polymyositis?

A

T-cell mediated cytotoxic process directed against muscle fibres

may be idiopathic or associated with connective tissue disorders

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4
Q

What serious condition is polymyositis associated with?

A

malignancy

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5
Q

How does dermatomyositis fit in with polymyositis?

A

it is a variant of the disease where skin manifestations are prominent, for example a purple (heliotrope) rash on the cheeks and eyelids

polymyositis + skin rashes

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6
Q

Which age group and gender is predominantly affected by polymyositis?

A

middle-aged

female:male 3:1

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7
Q

What are 6 clinical features of polymyositis?

A
  1. Proximal muscle weakness ± tenderness
  2. Raynaud’s
  3. Respiratory muscle weakness
  4. Interstitial lung disease e.g. fibrosing alveolitis or organising pneumonia
  5. Dysphagia
  6. Dysphonia
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8
Q

What kind of lung disease may be present in polymyositis?

A

interstitial lung disease e.g. fibrosing alveolitis or organising pneumonia

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9
Q

What are 5 important investigations to help diagnoise polymyositis?

A
  1. Elevated creatine kinase
  2. Other muscle enzymes (lactate dehydrogenase [LD], aldolase, AST and ALT) also elevated in 85-95% of patients
  3. EMG
  4. Muscle biopsy
  5. Anti-synthetase antibodies
    1. anti-Jo1 antibodies seen in pattern of disease with lung involvement, Raynaud’s and fever
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10
Q

Which type of polymyositis are anti-synthetase antibodies e.g. anti-Jo1 usually seen?

A

in the pattern of disease associated with lung involvement, fever and Raynauds

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11
Q

What is mnemonic to remember the elevated muscle enzymes in polymyositis?

A

CLAAA:

  • Creatine kinase
  • Lactate dehydrogenase
  • Aldolase
  • ALT
  • AST
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12
Q

Which muscles are affected by weakness in polymyositis?

A

bilateral, proximal (hip and shoulder girdle)

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13
Q

Over what time period does weakness develop in polymyositis?

A

usually over weeks to months

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14
Q

What are 3 types of muscle groups that become involved in polymyositis later in the disease and what can this lead to?

A
  1. Pharyngeal muscles: dysphonia/dysphagia
  2. Oesophageal muscles: dysphagia
  3. Respiratory muscles: poor ventilation with type 2 respiratory failure
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15
Q

What are 2 differentials for polymyositis/dermatomyositis?

A
  1. Steroid or statin-iduced myopathy
  2. Thyroid disease
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16
Q

What are 8 features specific to the presentation of dermatomyositis?

A
  1. Heliotrope rash - lilac discolouration of eyelid skin in addition to periorbital oedema
  2. Photosensitive
  3. Gottron’s papules which are scaly, erythematous papules over knuckles and extensor surfaces of knees and elbows
  4. Macular erythematous rash generally found on the head and neck, trunk or hands
  5. Mechanic’s hands: extremely dry, scaly hands with linar cracks on palmar and lateral aspects of fingers
  6. Periungual (nailfold) erythema (capillary dilatation)
  7. Cutaneous vasculitis which can present as rashes and lead to ulcers
  8. Calcinosis
17
Q

What are 4 extra-muscular features of polymyositis and dermatomyositis?

A
  1. Systemic upset (fever/ tiredness/ malaise/ weight loss)
  2. Joints (polyarthralgia)
  3. Pulmonary (interstitial lung disease)
  4. Cardiovascular (Raynaud’s phenomenon and myocarditis)
18
Q

What proportion of cases of poly/dermatomyositis are secondary to an underlying malignancy?

A

5-15%

19
Q

Of dermatomyositis and polymyositis, which has the stronger association with malignancy?

A

dermatomyositis

20
Q

What are the 5 types of cancers most commonly associated with polymyositis/dermatomyositis?

A
  1. Lung
  2. Oesophagus
  3. Breast
  4. Colon
  5. Ovary
21
Q

What are the 3 most important initial tests to perform on all patients in whom you suspect a diagnosis of poly/dermatomyositis?

A
  1. Muscle-derived serum elevation; creatine kinase is most sensitive indicator, level usuall paralells disease activity
  2. EMG
  3. Muscle biopsy - definitive diagnosis
22
Q

What are 2 advantages of measuring creatine kinase in suspected poly/dermatomyositis?

A
  1. Most sensitive indicator
  2. Level usually parallels disease activity, particularly in polymyositis
23
Q

What is the role of EMG when investigating poly/dermatomyositis?

A

confirms the myopathic pattern of the disorder and excludes a primary neurogenic disorder

24
Q

What do neurogenic disorders show on EMG (unlike in myositis)?

A

short duration and low amplitude polyphasic motor units on voluntary activation

25
Q

What investigation makes the definitive diagnosis of poly/dermatomyositis?

A

muscle biopsy

26
Q

What will muscle biopsy show in polymyositis?

A

endomysial inflammatory infiltrates

27
Q

What will muscle biopsy show in dermatomyositis?

A

perivascular, perimysial inflammatory infiltrate

28
Q

What must investigations look for in dermato/polymyositis, as well as to make the initial diagnosis?

A

look for underlying malignancy

29
Q

When polymyositis is associated wtih lung cancer how can it manifest?

A

para-neoplastic syndrome

30
Q

What is the mainstay of treatment of dermato/polymyositis?

A

corticosteroids - start at high dose

creatanine kinase monitored to guide rate of tapering the dose

31
Q

What is used to guide the tapering dose of corticosteroids in poly/dermatomyositis?

A

creatanine kinase

32
Q

What drugs may be needed as an add-on to corticosteroid treament in myositis?

A

additional immunosuppressants such as methotrexate or azathioprine as a steroid sparing agent

33
Q

Which drug occasionally helps with skin disease in dermatomyositis?

A

hydroxychloroquine

34
Q

What can be used to treat dermato/polymyositis in addition to pharmacological therapy?

A

physiotherapy

35
Q

What factor makes dermatomyositis more likely to be associated with cancer?

A

if they are of increased age

36
Q

What antibody are 80% of dermatomyositis patients positive for?

A

ANA (anti-nuclear antibody)

37
Q

In addition to ANA, what other type of antibodies are a proportion of patients with dermatomyositis positive for and what are 3 examples?

A

30% have antibodies against aminoacyl-tRNA synthetases (anti-synthetase antibodies) including:

  1. antibodies against histidine-tRNA ligase (also called Jo-1)
  2. antibodies to signal recognition particle (SRP)
  3. anti-Mi-2 antibodies

AIP: Acute weakness (18 decks)

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