Idiopathic Inflammatory Myopathies Flashcards
What are IMMs?
Autoimmune disorder where there is inflammation within the muscles
Polymyositis- chronic inflammation of muscles
Dermatomyositis- inflammation of skin and muscles
What are the symptoms of polymyositis?
Proximal muscle weakness No pain Muscle wasting Acute/insidious onset Weight loss Fever
Difficulty squatting and climbing stairs
What are symptoms of dermatomyositis?
Gottrons lesions
-scaly erythematous patches on knuckles/elbows/knees
Heliotropic rash
Photosensitive rash on back/shoulders/neck
Periorbital oedema
Sc calcinosis
PLUS polymyositis symptoms
What investigations are needed?
Bloods
-Serum CK >1000 due to muscle damage
ANA- most +ve
RF- 50% +ve
Myositis specific antibodies
- Anti- Jo1= polymyositis
- Anti-Mi 2= dermatomyositis
- ANA= dermatomyositis
EMG
MRI for abnormal muscle
Muscle biopsy- fibre necrosis with inflammatory infiltrate
How is it diagnosed?
The following must be present
- Clinical presentation
- Elevated CK
- Autoantibodies
- Supportive EMG
What is the management?
Steroids e.g. prednisolone Other therapies if steroid response is poor -DMARDs e.g. azathioprine -IV immunoglobulins -Biological therapy e.g. infliximab
Must screen for appropriate cancers as increased risk
If untreated polymyositis can affect resp muscles causing resp failure
What is inclusion body myositis?
Affects white males>50
Insidious onset of proximal and distal muscle wasting- can be asymmetrical
Muscle biopsy shows inflammatory infiltrate and vacuoles containing beta amyloid
Rarely responses to steroids etc.