Idiopathic inflammatory myopathies Flashcards
What are the 4 types?
Polymyositis
Dermatomyositis
Inclusion body myositis
Immune-mediate necrotising myopathy
What features do they all share?
Proximal skeletal muscle weakness
Evidence of immune mediated muscle inflammation
Which are associated with malignancy?
Dermatomyositis
Immune-mediate necrotising myopathy
Which is associated with statin exposure?
IMNM
What is the histopath of DM?
Perifascicular mononuclear cells > perifasicular atrophy
What is the histopath of PM?
Lymphocytes invade a myofibre
What is the histopath of IBM?
Vacuoles rimmed with basophilic granules
What is the histopath of IMNM?
Muscle fibre necrosis with sparse inflam infiltrate
What are the clinical features in DM and PM?
Symmetrical proximal muscle weakness >90%
Myalgias and muscle tenderness in 25-50%
What are some skin signs in DM?
Gottron's papules, Gottron's sign Shawl sign Heliotrope rash Periungal erythema, ragged cuticles Holster sign Facial erythema
What is anti-synthetase?
Mechanic’s hands
- Constitutional symptoms
- Myositis
- Raynaud’s
- ILD
- Non-erostive arthritis
What are the lab findings?
CK, transaminases, LDH, aldolase
How does CK correlate with weakness?
No linearly
What other investigations are indicated?
EMG - can be normal in 10%
MRI - hip to ankles
TTE, RFT, oesophageal
Age appropriate screening for malignancy
What Mx options are there for DM and PM?
High dose glucocorticoids - tapering over one year
Steroid sparing - azathioprine, methotrexate, IVIg, rituximab, PLEX
