dermatomyositis / polymyositis Flashcards
define myositis
Myositis is an autoimmune condition that causes muscle inflammation.
what is polymyositis
a condition of chronic inflammation of muscles.
what is dermatomyositis
connective tissue disorder where there is chronic inflammation of the skin & muscles.
causes of myositis
- underlying cancer
- a viral infection
- idiopathic
risk factors for myositis
- HLA genes
- female
pathophysiology of myositis
It is thought to be a T-cell-mediated cytotoxic process directed against muscle fibres.
signs and symptoms of myositis
- Proximal bilateral muscle weakness (difficulty standing from a chair, climbing stairs, or lifting overhead)
- Muscle pain
- Gottron lesions (scaly erythematous patches) on the knuckles, elbows, and knees)
- Heliotrope rash (purple rash on the face and eyelids)
- Periorbital oedema (swelling around the eyes)
- Photosensitive erythematous rash on the back, shoulders, and neck
difference between derma and poly myositis
Poly occurs without skin features.
Derma associated with skin features
diagnostic investigation for myositis
muscle fibre biopsy necrosis
other investigations for myositis
- Clinical features
- Elevated creatine kinase
- Autoantibodies
- High ALT, AST, LDH
- Electromyography (EMG)
- MRI
- Muscle biopsy
what is creatine kinase
This is an enzyme found in muscle cells and an increased amount is found in myositis.
what autoantibodies found in myositis
Anti-Jo-1 (polymyositis, but also in in dermatomyositis)
Anti-MI-2/ANAs only dermatomyosities
first line treatment for myositis
Corticosteroids - prednisolone
other treatment options for myositis
- immunosuppressants (azathioprine)
- IV immunoglobulins
- Biological therapy (infliximab, etanercept)
- physiotherapy/exercise to increase strength and function
