Muscle Disease: Polymyositis and Dermatosyitis Flashcards
what is polymyositis
idiopathic inflammatory syndrome that causes symmetrical proximal muscle weakness
what is dermatomyositis
clinically similar to polymyositis but also has cutaneous symptoms
epidemiology
both more common in women as they are autoimmune
peak incidence of 40-50
what group of patients have an increased risk of malignancy
all patients
particuarly men over the age of 50 with dermatomyositis
what type of cancers is it linked to
ovarian, breast, stomach, lung, bladder and colon
pathology
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
what do features on a muscle biopsy show
necrosis and regeneration of muscle fibres are accompanied by focal chronic inflammation and fibrosis
presentation
symmetrical, proximal muscle weakness
some patients have myalgia
what is the onset like
insidious
how is it often described by patients
difficulty with particular activities eg brushing hair
what are the cuteanous features seen in dermatomyositis
gottrons sign
helitrope rash
shawl sign
gottrons sign
helitrope rash
shawl sign
lung involvement
ILD
repiratory muscle weakness
what predisposes one to ILD
anti Jo 1 antibody
oesophageal
dysphagia secondary to oropharyngeal and oesophgeal involvement in 1/3 patients
dysphonia
what type of sign is oesophageal involvement
poor progostic
cardiac features
myocarditis
consitutional symptoms
fever, weight loss
what feature is often present in the hands
Raynaud’s
history
presenting symptoms
drugs - steroids or statins
FH
social history - alcohol and illicit drugs
what features are important in the FH
- FH of neuromuscular disease, exposure to myotoxic drugs and endocrinopathy absent
importance of patient having taken steroids or statin
- 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
examination
confrontational testing
isotonic testing
what is isotonic testing
measuring of muscle stamina over time
investigations
muscle enzymes
blood tests
inflammatory markers raised
what do muscle enzymes show
serum CK raised
autoantibodies
ANA and anti Jo 1
EMG
findings abnormal in most patients
passing a low electrical current through the muscle to see if it conducts
what is the definitive test
muscle biopsy
MRI
can localise the extent of muscle involvement
show muscle inflammation, oedema, fibrosis and calcification
management
glucocorticoids (prednisolone) combined with IS drugs eg methotrexate/azathioprine
biologic drugs can also be used
what may need to be prescribed with the steroid
- Side effect of peptic ulceration – prescribe PPI when necessary, e.g. omeprazole
prognosis
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
what is inclusion body myositis
inflammatory muscle disease characterised by slow weakening and wasting of proximal and distal muscles
how does the pathogenesis of inclusion body myositis differ to that of poly and dermato myositis
it is autoimmune and destructive, the other two are not destructive
what is includsion body myositis often misdiagnosed as
polymyositis
who does inclusion body myositis occur in
OVER 50 (PM: 40-60)
more common in men
is the muscle weakness in inclusion body myositis symmetrical?
no asymmetrical, symmetrical in PM
diagnostic test for inclusion body myositis
muscle biopsy - inclusion bodies
CK levels in inclusion body myositis
raised but not as much as in PM
inclusion body myositis prognosis
poor response to therapy
which muscles are frequently involved in inclusion body myositis, and how does this present
quadriceps - frequent falling
what is the classical type of facial weakness occurring in inclusion body myositis
facial weakness sparing extra ocular muscles
are fine motor tasks affected more in PM or inclusion body myositis
inclusion body myositis
what happens to reflexes in inclusion body myositis
lose patellar reflexes
