Polymyositis,dermatomyositis & Inclusion Body Myositis Flashcards
What are the similarities between polymyositis and dermatomyositis?
Idiopathic
Cause symmetrical proximal muscle weakness
Cause muscle inflammation
Result in abnormal EMG findings
What are the characteristics of polymyositis?
Rare disease occurs in adults Sometimes associated with malignancy Symmetric weakness Proximal muscle involvement Associated with autoimmune disease Diagnosis of exclusion
What are some medications that can cause symptoms similar to polymyositis?
Statins
D-Penicillamine
Zidovudine
What are the characteristics of dermatomyositis?
Rare disease
Affects more women than men
Bimodal incidence in childhood and adulthood
Present earlier than polymyositis due to rash
Associated with malignancy
What are the signs and symptoms of dermatomyositis?
Heliotrope rash- on upper eye lids Gottron’s sign- MCP & IP joints V-sign- poikilodermia on chest Shawl sign- v sign on upper back Mechanics hands- dry cracked hands Dilated capillary loops at cuticles Psoriatic scalp rash Holster sign-poikiloderma on proximal thigh
What are the cancers most commonly associated with dermatomyositis?
Ovarian Colon Melanoma Breast Non-Hodgkins lymphoma Nasopharyngeal
How to diagnose polymyositis and dermatomyositis ?
Increased muscle enzymes: CPK ( elevated in 95%, value above 1000), AST,ALT
EMG changes showing irritability
Muscle biopsy- gold standard for diagnosis
ANA-80% of the time
What is the presentation of muscle biopsy in dermatomyositis?
Perifasicular atrophy and inflammatory infiltrates
What is the presentation of the biopsy in polymyositis ?
Scattered inflammation with lymphocytic invasion
What are the autoantibodies found with polymyositis and dermatomyositis ?
Anti-Jo-1- Likely associated with ILD
Anti-SRP
Anti-Mi-2
What are the characteristics of inclusion body myositis (IBM)?
Affects more men than women Most often caucasians over 50 Cause asymmetric weakness Distal muscles affected earlier in the disease Facial muscle involvement is common Onset over years
How to diagnose IBM?
Biopsy: vacuoles rimmed by mitochondria, lymphocytic infiltrates and filamentous inclusions
CPK elevation mild or absent
No autoantibodies
How to treat dermatomyositis and polymyositis ?
Glucocorticoids
Immunosupressants
Immunomodulators
What is the glucocorticoids regimen?
High dose prednisone is number 1 Initiale ASAP Continue high dose for 3-4 weeks Taper over 1 year Treatment should be based off clinical improvement not CPK improvement Watch for steroid myopathy
What is the immunosuppressant regimen?
Indicated in inadequate response to steroids, rapidly progressive disease
Azathioprine
Methotrexate
