Polymyositis and dermatomyositis Flashcards
What does polymyositis result in?
Symmetrical, proximal muscle weakness
What does dermatomyositis result in?
Clinically similar symmetrical proximal muscle weakness and cutaneous manifestations
Who is affected by these conditions?
2:1 w:m
adults 20+ (45-60)
What is the pathogenesis of polymyositis?
- T-cell mediated cytotoxic process against unidentified muscle antigens
- CD8 T cells, macrophages surround, invade and destroy healthy muscle fibres
What is detected in 60-80% of patients?
autoimmune response to nuclear and cytoplasmic auto antigens
Serum autoantibodies
- Non-specific (ANA, anti-RNP)
- Specific (anti-Jo-1)
What investigations are done in polymyositis?
inflammatory markers raised
high serum CK (10X normal)
autoantibodies- ANA, anti-Jo-1, anti-SRP
MRI to gauge extent of muscle involvement
EMG 90% of patients abnormal
Muscle biopsy- inflammation, necrosis, regeneration
How does polymyositis present?
Symmetrical, proximal muscle weakness in upper and lower extremities. Insidious onset, difficulty climbing stairs.
Myalgia
Dysphagia
ILD
How is polymyositis managed?
prednisolone (initially around 40mg) and immunosuppressive drugs such as methotrexate or azathioprine.
What is the prognosis of polymyositis?
usually slowly responds to treatment
30% patients residual weakness
do less well with age
What are the cutaneous features of dermatomyositis?
V-shaped rash over chest
Gottron’s papules
Heliotrope rash
How is dermatomyositis managed?
The same ad polymyositis
What is the risk associated with dermatomyositis?
Risk of malignancy 25% of patients 5 years following diagnosis -breast -ovarian -lung -colon -oesophagus -bladder
What screening should be undergone in dermatomyositis?
Malignancy should be screened for at time of diagnosis
