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Polymyositis/Dermatomyositis (Diagnosis (Muscle enzymes: creatine kinase,…
Polymyositis/Dermatomyositis
Definition:
this is a rare condition that is unknown aetiology. It is inflammation and necrosis of the skeletal muscle fibres
Inflammation of the muscle is polymyositis
Inflammation of the skin is dermatomyositis
Can result in interstitial lung disease
Risk Factors
Genetic predisposition: those who have HLA B8/DR3 (Sjogrens)
People who have other autoimmune diseases are more likely to have polymyositis and dermatomyositis
Viral causes: coxsackie, rubella and influenza
Epidemiology
Very rare
Affects both adults and children
More common in females
Clinical Presentation (will be different for polymyositis and dermatomyositis)
Polymyositis
Can cause involvement of the respiratory systems --> respiratory failure
Patients have difficulities squatting, going upstairs or raising a chair above their head
Symmetrical progressive muscle weakness and wasting to pelvic and shoulder muscles
Dermatomyositis
Characteristic skin changes: hellotrope discolouration of eyelids, scaly erythematous plaques on the knuckles
Arthralgia, dysphagia and oesphageal muscle involvement and Raynauds!
INCREASED INCIDENCE WITH MALIGNANCY
GENERAL SYMPTOMS
Muscle pain and stiffness
Joint pain and stiffness
Problems catching breath
Skin changes
Treatment
Prednisolone until 1 month after a relapase
Clinical Relapse: use methotrexate, ciclosporin or azathioprine
Bed Rest
Hydroxychloroquine to help with the skin disease
Diagnosis
Muscle enzymes: creatine kinase, aminotransferases, lactate dehydrogenase and aldolase are all raised
ESR not normally raised
Muscle biopsy
Serum antibodies: ANA. RF and Myositis Specific antibodies (MSA) are all postive
Electromyography (EMG)
MRI can show the inflamed muscle
DIFFERENTIAL DIAGNOSIS
Myasthenia Gravis
Myopathies
Other connective tissue disorders