Muscle Disease: Polymyositis and Dermatosyitis

Question 1

what is polymyositis

Answer 1

idiopathic inflammatory syndrome that causes symmetrical proximal muscle weakness

Question 2

what is dermatomyositis

Answer 2

clinically similar to polymyositis but also has cutaneous symptoms

Question 3

epidemiology

Answer 3

both more common in women as they are autoimmune

peak incidence of 40-50

Question 4

what group of patients have an increased risk of malignancy

Answer 4

all patients

particuarly men over the age of 50 with dermatomyositis

Question 5

what type of cancers is it linked to

Answer 5

ovarian, breast, stomach, lung, bladder and colon

Question 6

pathology

Answer 6

T cell mediated cytotoxic proces that is directed against unidentified muscle antigens

CD8 T cells surround non necrotic muscle fibres and eventually invade and destroy them

Question 7

what do features on a muscle biopsy show

Answer 7

necrosis and regeneration of muscle fibres are accompanied by focal chronic inflammation and fibrosis

Question 8

presentation

Answer 8

symmetrical, proximal muscle weakness

some patients have myalgia

Question 9

what is the onset like

Answer 9

insidious

Question 10

how is it often described by patients

Answer 10

difficulty with particular activities eg brushing hair

Question 11

what are the cuteanous features seen in dermatomyositis

Answer 11

gottrons sign

helitrope rash

shawl sign

Question 12

Answer 12

gottrons sign

Question 13

Answer 13

helitrope rash

Question 14

Answer 14

shawl sign

Question 15

lung involvement

Answer 15

ILD

repiratory muscle weakness

Question 16

what predisposes one to ILD

Answer 16

anti Jo 1 antibody

Question 17

oesophageal

Answer 17

dysphagia secondary to oropharyngeal and oesophgeal involvement in 1/3 patients

dysphonia

Question 18

what type of sign is oesophageal involvement

Answer 18

poor progostic

Question 19

cardiac features

Answer 19

myocarditis

Question 20

consitutional symptoms

Answer 20

fever, weight loss

Question 21

what feature is often present in the hands

Answer 21

Raynaud’s

Question 22

history

Answer 22

presenting symptoms

drugs - steroids or statins

FH

social history - alcohol and illicit drugs

Question 23

what features are important in the FH

Answer 23

• FH of neuromuscular disease, exposure to myotoxic drugs and endocrinopathy absent

Question 24

importance of patient having taken steroids or statin

Answer 24

• Statins are associated with inflammatory myopathies (e.g. polymyositis and dermatomyositis). Present as raised CK and proximal muscle weakness following statin use, symptoms persist after discontinuation of the drug
• Steroids can cause proximal myopathy as they alter protein metabolism, reducing protein synthesis
• Must rule out these causes

Question 25

examination

Answer 25

confrontational testing isotonic testing

Question 26

what is isotonic testing

Answer 26

measuring of muscle stamina over time

Question 27

investigations

Answer 27

muscle enzymes blood tests inflammatory markers raised

Question 28

what do muscle enzymes show

Answer 28

serum CK raised

Question 29

autoantibodies

Answer 29

ANA and anti Jo 1

Question 30

EMG

Answer 30

findings abnormal in most patients passing a low electrical current through the muscle to see if it conducts

Question 31

what is the definitive test

Answer 31

muscle biopsy

Question 32

MRI

Answer 32

can localise the extent of muscle involvement show muscle inflammation, oedema, fibrosis and calcification

Question 33

management

Answer 33

glucocorticoids (**prednisolone**) combined with IS drugs eg methotrexate/azathioprine biologic drugs can also be used

Question 34

what may need to be prescribed with the steroid

Answer 34

* Side effect of peptic ulceration – prescribe PPI when necessary, e.g. omeprazole

Question 35

prognosis

Answer 35

usually responds slowly to treatment around 30% patients left with some residual weakness older patients and those who present later tend to do less well

Question 36

what is inclusion body myositis

Answer 36

inflammatory muscle disease characterised by slow weakening and wasting of proximal and distal muscles

Question 37

how does the pathogenesis of inclusion body myositis differ to that of poly and dermato myositis

Answer 37

it is autoimmune and destructive, the other two are not destructive

Question 38

what is includsion body myositis often misdiagnosed as

Answer 38

polymyositis

Question 39

who does inclusion body myositis occur in

Answer 39

OVER 50 (PM: 40-60) more common in men

Question 40

is the muscle weakness in inclusion body myositis symmetrical?

Answer 40

no asymmetrical, symmetrical in PM

Question 41

diagnostic test for inclusion body myositis

Answer 41

muscle biopsy - inclusion bodies

Question 42

CK levels in inclusion body myositis

Answer 42

raised but not as much as in PM

Question 43

inclusion body myositis prognosis

Answer 43

poor response to therapy

Question 44

which muscles are frequently involved in inclusion body myositis, and how does this present

Answer 44

quadriceps - frequent falling

Question 45

what is the classical type of facial weakness occurring in inclusion body myositis

Answer 45

facial weakness sparing extra ocular muscles

Question 46

are fine motor tasks affected more in PM or inclusion body myositis

Answer 46

inclusion body myositis

Question 47

what happens to reflexes in inclusion body myositis

Answer 47

lose patellar reflexes