Polymyositis and dermatomyositis Flashcards
What are Polymyositis and dermatomyositis?
Autoimmune disorders where there is inflammation in the muscles (myositis).
Polymyositis is a condition of chronic inflammation of muscles.
Dermatomyositis is a connective tissue disorder where there is chronic inflammation of the skin and muscles.
Causes of raised CK
Rhabdomyolysis
Polymyositis and dermatomyositis
AKI
MI
Statins
Strenuous exercise
What are polymyositis and dermatomyositis associated with?
Can be caused by an underlying malignancy (paraneoplastic syndromes)
Most common associated cancers:
- Lung
- Breast
- Ovarian
- Gastric
Presentation of polymyositis and dermatomyositis
Muscle pain, fatigue and weakness
- Bilateral, typically the proximal muscles
- Mostly the shoulder and pelvic girdle
- Develops over weeks
Dermatomyositis also has skin features (not seen in poly):
- Gottron lesions (scaly erythematous patches) on the knuckles, elbows and knees
- Photosensitive erythematous rash on the back, shoulders and neck
- Purple rash on the face and eyelids
- Periorbital oedema (swelling around the eyes)
- Subcutaneous calcinosis (calcium deposits in the subcutaneous tissue)
What autoantibodies are associated with the conditions of polymyositis and dermatomyositis?
Anti-Jo-1 antibodies: polymyositis (but often present in dermatomyositis)
Anti-Mi-2 antibodies: dermatomyositis.
Anti-nuclear antibodies: dermatomyositis.
Diagnosis and investigations of polymyositis and dermatomyositis
CK - elevated
Autoantibodies e.g. Anti-Jo-1, Anti-Mi-2
EMG
Muscle biopsy can be used for definitive diagnosis
Management of polymyositis and dermatomyositis
Refer to rheumatology for management
First line is corticosteroids
- Other options are immunosuppressants (e.g. azathioprine), IVIG, biologics
Assess for underlying cancer in new cases
Physio to improve muscle strength
