Myositis

Question 1

Define myositis?

Answer 1

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

Question 2

What is the ratio of women to men affected by myositis when there is no malignancy, compared to when there is malignancy?

Answer 2

Women to men ratio is 2.5:1 when there is no malignancy, but is 10:1 when there is malignancy

Question 3

What is the incidence of myositis?

Answer 3

2-10 in 1,000,000

Question 4

What are the peak age onsets of myositis in children and adults?

Answer 4

Juvenile myositis peak age onset is 5-18 years

Adult myositis has peak age onset 50 and older

Can still affect any age

Question 5

Is dermatomyositis associated with malignancy, if so how can this guide treatment of DM?

Answer 5

Dermatomyositis is associated with malignancy in elderly, so DM can regress if malignancy is treated

Question 6

Describe the hallmark presentation of myositis in terms of clinical features and onset?

Answer 6

Usually painless, proximal muscle weakness with/without rash that progresses with insidious onset (3-6 months)

Question 7

How can myositis affect the larynx/voice box, and what is the clinical presentation?

Answer 7

Muscles around larynx/voice box become tense, which causes dysphonia (abnormal voice)

Question 8

Give 2 clinical features of GI involvement in myositis, and what muscles are involved?

Answer 8

Weakening of throat muscles in GI involvement causes dysphagia (difficulty swallowing), regurgitation

Question 9

When an individual with myositis presents with serious breathing problems, what complication of myositis does this indicate?

Answer 9

Lung fibrosis

Question 10

Where does calcinosis occur in body, in individuals with myositis?

Answer 10

Calcinosis in muscles, skin and other connective tissues

Question 11

What is the difference between Gottron’s papules and Gottron’s sign in DM?

Answer 11

Gottron’s papules: scaly, erythematous palpable plaques over finger joints

Gottron’s sign: erythematous, flat, non-palpable (macular) rash over finger joints

Question 12

Describe the 2 types of rashes that can present in dermatomyositis?

Answer 12

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

Question 13

What 2 conditions can be caused by joint involvement in dermatomyositis?

Answer 13

Polyarthralgia, arthritis

Question 14

Does arthritis caused by joint involvement in dermatomyositis present in same way as RA?

Answer 14

DM arthritis usually affects small and medium joints symmetrically, similar to RA but less degenerative

Question 15

Give 2 clinical features of heart involvement in myositis?

Answer 15

Myositis can cause myocarditis, which presents with rhythm disturbance and congestive heart failure

Question 16

In myositis, what serum muscle enzymes are elevated and what does this indicate?

Answer 16

Elevated levels of CK (95% cases), lactate dehydrogenase, aspartate and alanine aminotransferases

Elevation of serum muscle enzymes suggests ongoing muscle tissue damage

Question 17

What is the myositis immunoblot/line blot used to identify?

Answer 17

myositis-associated autoantibodies

Question 18

In myositis, what will biopsy of affected muscle show?

Answer 18

Biopsy shows inflammatory cells (mostly lymphocytes) in perivascular and interstitial areas surrounding myofibrils

Question 19

In myositis, what 3 features are shown by electromyography of affected muscle, and what 2 types of disorders do these features indicate?

Answer 19

Irritated myofibrils

Complex repetitive discharges

Complex potentials on muscle contraction

Occur in neurogenic and myopathic disorders

Question 20

What radiographic imaging is used for myositis, and what is the feature that aids diagnosis?

Answer 20

MRI shows streaky/patchy infiltration of muscle

Question 21

What criteria is used to diagnose myositis, what is its probability of correct diagnosis and what 6 factors are evaluated?

Answer 21

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

Question 22

What is the usual initial management of myositis?

Answer 22

Prednisolone 1 mg/kg daily

Question 23

Give 3 examples of medications that can be prescribe to treat myositis other than prednisolone?

Answer 23

Immunosuppressants such as MTX, azathioprine, cyclosporine

Question 24

Compare the age onset of PMR and polymyositis?

Answer 24

Polymyositis can occur at any age but PMR almost always occurs over age 50

Question 25

Compare the areas affected of PMR and polymyositis?

Answer 25

Polymyositis affects any proximal muscle, but PMR mostly affects shoulder and hip pain

Question 26

Compare the CPK levels of PMR and polymyositis?

Answer 26

Polymyositis has elevated CPK level due to muscle damage, but PMR has normal CPK level as there is no muscle involvement/damage

Question 27

Compare the rareness and severity of PMR and polymyositis?

Answer 27

Polymyositis is rare and needs referral, but PMR is common and often managed by GPs