inflammatory myopathies

Question 1

polymyositis defintion

Answer 1

autoimmune inflammatory myopathy which causes symmetrical muscle weakness

Question 2

dermatomyositis definition

Answer 2

exact same disease as polymyositis but with cutaneous features

Question 3

who is both polymyositis and dermatomyositis more common in

Answer 3

2x more common in woman in their 40-60s

Question 4

pathophysiology

Answer 4

T cell mediated cytotoxic process directed against unknown muscle antigens, CD8 T cells and macrophages invade and destroy healthy muscle fibres

Question 5

presentation of polymyositis

Answer 5

• symmetrical proximal muscle weakness of a gradual onset
• patients usually complain of difficulty doing specific tasks such as crushing their hair or climbing stairs
• affects the lower limbs more severely than upper limbs

Question 6

presentation of dermatomyositis

Answer 6

• same as polymyositis but with cutaneous features
• heliotrope eyelids= purple rash on eyelids
• gottrons papules= purple plaques on knuckles
• shawl sign= purple rah over back and chest

Question 7

other features of polymyositis and dermatomyositis

Answer 7

• myalgia but the pain is usually mild
• lungs: interstitial lung disease
• oesophagus: dysphagia is a poor prognostic sign
• cardiac: myocarditis
• weight loss

Question 8

why should weight loss be taken seriously in both polymyositis and dermatomyositis

Answer 8

9% risk of malignant in polymyositis and 15% risk of malignancy in dermatomyositis, the risk of malignancy is greater in males over 40 years old

Question 9

which malignant cancers usually occur in dermatomyositis and polymyositis

Answer 9

ovarian, breast, stomach, lung, bladder

Question 10

definitive investigation which is gold standard

Answer 10

muscle biopsy shows perivascular inflammation and muscle necrosis

Question 11

other investigations

Answer 11

• creatinine kinase is 10x normal limit
• raised inflammatory markers
• anti-jo-1 antibody
• MRI
• Electromyography: EMG

Question 12

antibody in polymysotis and dermatomyositis

Answer 12

anti-jo-1

Question 13

inclusion body myositis

Answer 13

occurs in men over 50 and is not an autoimmune disease so is NOT associated with any antibody

Question 14

inclusion body myositis presentation

Answer 14

• more insidious onset over many years

- often asymmetrical causing distal muscle weakness

Question 15

investigations of inclusion body myositis

Answer 15

creatinine kinase is a little elevated but nothing off that in polymyositis and deramtomyositsi

Question 16

treatment of inclusion body myositis

Answer 16

THERE IS NONE!!!

Question 17

treatment of polymyositis and dermatomyositis

Answer 17

• 40mg of prednisolone initially and over-time reduce dose of steroid and combine with methotrexate or azathioprine
• if these fail then IV immunoglobulin or Rituximab