Myositis Flashcards
Define myositis?
Autoimmune connective tissue disease associated with different antibodies and immunological features, that is characterised by chronic inflammation of skeletal muscle (polymyositis), sometimes skin (dermatomyositis) and lung disease
What is the ratio of women to men affected by myositis when there is no malignancy, compared to when there is malignancy?
Women to men ratio is 2.5:1 when there is no malignancy, but is 10:1 when there is malignancy
What is the incidence of myositis?
2-10 in 1,000,000
What are the peak age onsets of myositis in children and adults?
Juvenile myositis peak age onset is 5-18 years
Adult myositis has peak age onset 50 and older
Can still affect any age
Is dermatomyositis associated with malignancy, if so how can this guide treatment of DM?
Dermatomyositis is associated with malignancy in elderly, so DM can regress if malignancy is treated
Describe the hallmark presentation of myositis in terms of clinical features and onset?
Usually painless, proximal muscle weakness with/without rash that progresses with insidious onset (3-6 months)
How can myositis affect the larynx/voice box, and what is the clinical presentation?
Muscles around larynx/voice box become tense, which causes dysphonia (abnormal voice)
Give 2 clinical features of GI involvement in myositis, and what muscles are involved?
Weakening of throat muscles in GI involvement causes dysphagia (difficulty swallowing), regurgitation
When an individual with myositis presents with serious breathing problems, what complication of myositis does this indicate?
Lung fibrosis
Where does calcinosis occur in body, in individuals with myositis?
Calcinosis in muscles, skin and other connective tissues
What is the difference between Gottron’s papules and Gottron’s sign in DM?
Gottron’s papules: scaly, erythematous palpable plaques over finger joints
Gottron’s sign: erythematous, flat, non-palpable (macular) rash over finger joints
Describe the 2 types of rashes that can present in dermatomyositis?
Erythematous rash on malar region, nasolabial folds, upper eyelid, nose bridge
Heliotrope/violaceous rash, which is red/purple discolouration on/around eyelid accompanied by eyelid swelling
What 2 conditions can be caused by joint involvement in dermatomyositis?
Polyarthralgia, arthritis
Does arthritis caused by joint involvement in dermatomyositis present in same way as RA?
DM arthritis usually affects small and medium joints symmetrically, similar to RA but less degenerative
Give 2 clinical features of heart involvement in myositis?
Myositis can cause myocarditis, which presents with rhythm disturbance and congestive heart failure
In myositis, what serum muscle enzymes are elevated and what does this indicate?
Elevated levels of CK (95% cases), lactate dehydrogenase, aspartate and alanine aminotransferases
Elevation of serum muscle enzymes suggests ongoing muscle tissue damage
What is the myositis immunoblot/line blot used to identify?
myositis-associated autoantibodies
In myositis, what will biopsy of affected muscle show?
Biopsy shows inflammatory cells (mostly lymphocytes) in perivascular and interstitial areas surrounding myofibrils
In myositis, what 3 features are shown by electromyography of affected muscle, and what 2 types of disorders do these features indicate?
Irritated myofibrils
Complex repetitive discharges
Complex potentials on muscle contraction
Occur in neurogenic and myopathic disorders
What radiographic imaging is used for myositis, and what is the feature that aids diagnosis?
MRI shows streaky/patchy infiltration of muscle
What criteria is used to diagnose myositis, what is its probability of correct diagnosis and what 6 factors are evaluated?
EULAR criteria idiopathic inflammatory myositis online tool
Probability over 50% of correct classification
Criteria evaluates age onset of first symptom, involvement of muscles, skin, GI, blood tests and biopsy results
What is the usual initial management of myositis?
Prednisolone 1 mg/kg daily
Give 3 examples of medications that can be prescribe to treat myositis other than prednisolone?
Immunosuppressants such as MTX, azathioprine, cyclosporine
Compare the age onset of PMR and polymyositis?
Polymyositis can occur at any age but PMR almost always occurs over age 50
Compare the areas affected of PMR and polymyositis?
Polymyositis affects any proximal muscle, but PMR mostly affects shoulder and hip pain
Compare the CPK levels of PMR and polymyositis?
Polymyositis has elevated CPK level due to muscle damage, but PMR has normal CPK level as there is no muscle involvement/damage
Compare the rareness and severity of PMR and polymyositis?
Polymyositis is rare and needs referral, but PMR is common and often managed by GPs
