Muscle Diseases Flashcards
What is polymyositis?
an idiopathic, inflammatory myopathy that causes symmetrical, proximal muscle weakness
What is dermatomyositis?
clinically similar to polymyositis but with cutaneous manifestations
which groups are most commonly affected by polymyositis?
women; 45-60years
What is the pathogenic mechanism behind polymyositis?
T cell mediated process whereby macrophages and T cells surround and destroy healthy non-necrotic muscle tissue against unidentified muscle antigens
Autoantibodies in polymyositis
Specific: Anti-Jo1, Anti-SRP Non-specific: ANA and anti-cytoplasmic
Presentation of polymyositis
symmetrical proximal muscle weakness of upper and lower limbs, insidious onset often noticed when tasks become difficult i.e. climbing stairs. Dysphagia secondary to oropharyngeal and oesophageal involvement occurs in 33% and is a poor prognostic indicator
Occurs in 15-30% of polymyositis patients esp. those positive with Anti-Jo1
interstitial lung disease
Which investigations should be ordered for polymyositis? (6)
Inflammatory markers, CK, Autoantibodies, MRI, EMG, Muscle biopsy
Results of CK and inflammatory markers in polymyositis
raised inflammatory markers and CK very raised, often 10 fold
MRI results for polymyositis
oedema, inflammation and scarring of muscle
EMG results in polymyositis
abnormal in 90%
Management of polymyositis
prednisolone (40mg), immunosuppression (methotrexate or azathioprine)
Rashes associated with dermatomyositis (3)
Shawl, V-shaped rash over chest and shoulders; Gottrons papules (over the knuckles); Heliotrope purple rash around eyes
Polymyositis/Dermatomyositis have an associated risk of malignancy - TRUE/FALSE
TRUE - around 25% of patients will develop cancer within the first 5 years of diagnosis
Common cancers associated with polymyositis/dermatomyositis (6)
breast, ovarian, lung, colon, oesophageal, bladder
