Inflammatory Myopathies

Question 1

What is polymyositis?

Answer 1

idiopathic inflammatory myopathy characterised by muscle fibre necrosis, degeneration and regeneration and inflammatory cell infiltrate

Question 2

What is the pathophysiology of polymyositis?

Answer 2

T-cell–mediated cytotoxic process directed against unidentified muscle antigens. CD8 T cells, along with macrophages, initially surround healthy nonnecrotic muscle fibers and eventually invade and destroy them

Question 3

What antibodies are present in polymyositis

Answer 3

ANA
anti-RNP
anti-Jo-1
anti-SRP

Question 4

What is the common population that is affected by polymyositis? male or female?

Answer 4

female x2

40-50 years

Question 5

What is the presentation of polymyositis?

Answer 5

painless progressive muscle weakness
usually symmetrical and proximal
Dysphagia secondary to oropharyngeal and esophageal involvement - poor prognostic sign.
Interstitial lung disease (anti-Jo)

Question 6

What is dermatomyositis?

Answer 6

the same as polymyositis but with a characteristic helitrope rash, V shaped rash on chest, and gottrons papules on fingers

Question 7

What are the investigations for P and D?

Answer 7

raised inflammatory markers
raised CK
Autoantibodies include ANA, anti-Jo-1 and anti-SRP, anti-RNP
MRI - shows muscle involvement
Electromyographic (EMG)
Muscle biopsy - shows fibrosis, inflammation etc

Question 8

What is the management for P and D?

Answer 8

40mg prednioslone and methotrexate

Question 9

Is there an increase in malignancy for P and D?

Answer 9

YES