Myositis Flashcards
What are the 2 types of myositis?
Polymyositis
Dermatomyositis
What is myositis (Polymyositis and dermatomyositis)?
Autoimmune condition causing muscle inflammation
How do Polymyositis and dermatomyositis both typically present?
Gradual onset, symmetrical proximal muscle weakness
Sometimes can have muscle pain (not always)
What is meant by Polymyositis and dermatomyositis both causing proximal muscle weakness?
Weaknesss of the tops of the arms and tops of the legs (shoulders and thighs)
What can trigger Polymyositis or dermatomyositis?
Underlying cancer (so then called paraneoplastic syndromes)
Viral infections (HIV or coxsackie virus)
HLA genes(risk factors)
How does dermatomyositis present differently to polymyositis?
Dermatomyositis has skin changes
What skin changes can be seen in dermatomyositis?
Gottron lesions
Heliotrope rash
Periorbital oedema
Photosensitive erythematous rash
What are gottron lesions in dermatomyositis?
Scaly erythematous patches on the knuckles elbows and knees
What is a heliotrope rash seen in dermatomyositis?
Purple rash on face and eyelids
Where on the body is a photosensitive erythematous rash typically seen with dermatomyositis?
Back
Shoulders
Neck
What investigations are done to diagnose polymyositis or dermatomyositis?
Creatine kinase levels
Electromyography
MRI
MUSCLE BIOPSY (ONLY DEFINITIVE WAY TO DIAGNOSE)
Autoantibodies
What autoantibodies are commonly raised with polymyositis?
Anti-jo-1 antibodies
What investigation will be raised with Polymyositis/dermatomyositis but normal with Polymyalgia rheumatica?
CK levels (Creatine kinase)
What are some causes of raised creatine kinase that is not Polymyositis or dermatomyositis?
Rhabdomyolysis
AKI
MI
Statins
Strenuous exercise
Why may a patient with polymyositis or dermatomyositis present with struggling to get out of chair, shortness of breath, difficulty swallowing and voice changes?
Weakness of diaphragmatic muscles for SOB
Weakness of oesophageal muscles and vocal cords
What is the pathophysiology of dermatomyositis?
Causes vasculitis which leads to ischaemic infarction and atrophy at the periphery of fascicles in the muscle (perifasicular atrophy)
What is the pathophysiology of polymyositis?
Fibre necrosis occurs due to endomysial cellular infiltration of the muscle
What does it seem is linked to Polymyositis and dermatomyositis?
Risk of malignancy
What is the treatment for polymyositis and dermatomyositis?
Prompt (Prednisolone) corticosteroids (1mg/kg up to 60mg)
Then slowly ween off steroids once under control (if not under control on steroids give methotrexate or azathioprine)
What do you do treatment wise if a pateitn relapses with polymyositis or dermatomyositis?
1st relapse: return to Prednisolone dose that kept them in remission
2nd relapse/corticossteroids never worked: switch to methotrexate or azathioprine
What medication can you give to treat the rash in dermatomyositis?
Hydroxychloroquine
What is a side effect of hydrorxychloroquine?
N+V
Diarrhoea
Ophthamotoxic = bullseye maculopathy
QT prolongation
What are some causes of proximal muscle weakness?
Dermatomyositis
Polymyositis
Myasthenia gravis
Thyroid disease
Steroids
Statins
Osteomalacia
Hyperparathyroidism
Cushings
When treating a patietn with long term corticosteroids, what other medications might you want to give?
Bisphosphonates like allendronic acid or zolendronic. Acid
PPIs (omeprazole)
What must you do before giving a patient azithioprine?
Measure TPMT levels
What must be done before giving a patient Azathioprine?
Measure TPMT levels
