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Background
- Idiopathic inflammatory myopathy causing symmetric proximal muscle weakness, elevated CK, and characteristic EMG findings
Clinical Features
- Symmetrical proximal muscle weakness with insidious onset
- Generally painless (though 30% have myalgia)
- Difficulty with kneeling, climbing stairs, combing hair, or rising from a seated position
- Weak neck extensors causing difficulty of holding head up
- Associated arthralgias
Differential Diagnosis
- Neuromuscular weakness
- Upper motor neuron:
- Lower motor neuron:
- Spinal and bulbar muscular atrophy (Kennedy's syndrome)
- Spinal cord disease:
- Peripheral nerve disease:
- Neuromuscular junction disease:
- Muscle disease:
- Non-neuromuscular weakness
- Can't miss diagnoses:
- Emergent Diagnoses:
- Other causes of weakness and paralysis
Evaluation
Workup
- CBC
- ESR
- CRP
- CK: Most sensitive muscle enzyme
- Urinalysis
- Consider:
- LDH
- AST/ALT
- Aldolase
- RF
- ANA
- Anti-Jo-1
- Myositis antibody panel
Diagnosis
- Typically requires muscle biopsy
Management
- Prednisone 1mg/kg/day for 4-8 weeks until CK returns to reference range
- Other treatments that rheum may prescribe:
- Methotrexate as second line for poor response to corticosteroids
- Other agents with less evidence: IVIG, TNF Inhibitors
- Assess for interstitial lung disease
- CXR, consider CT chest
- Pulmonary function tests (PFTs)
- Screen for associated malignancy, especially:[1]
- Ovarian
- Lung
- Pancreatic
- Stomach
- Colorectal
- Lymphoma
- Bladder
Disposition
- Rheumatology or neurology consultation either in ED or as outpatient depending on severity of symptoms
See Also
References
- ↑ Hill CL et al. Frequency of specific cancer types in dermatomyositis and polymyositis: a population-based study. Lancet. 2001 Jan 13;357(9250):96-100.