Idiopathic Inflammatory Myopathies

Idiopathic Inflammatory Myopathies Major forms: Polymyositis Dermatomyositis Inclusion Body Myositis

Classification of Idiopathic Inflammatory Myopathies Polymyositis and Dermatomyositis Polymyositis, primary, adult Dermatomyositis, primary, adult Myositis with malignancy Juvenile dermatomyositis Myositis in connective tissue diseases Inclusion body myositis Other: Granulomatous, Eosinophilic, Localized, Proliferative, Orbital

Idiopathic Inflammatory Myopathies Incidence PM/DM: 0.1-1 cases/100K/yr Less than frequency of scleroderma which is less than for lupus Prevalence: 3-10 cases/100,000 Children: DM>PM>IBM Adult<50: PM>DM>IBM Using clinical definition of PM Adult>50: IBM>PM>DM Malignancy: DM>PM>IBM Peak: PM/DM 45 - 64 yrs; IBM older Juvenile peak approx 10 y PM/DM F>M; IBM M>F

Presentation of Idiopathic Inflammatory Myopathies Proximal muscle weakness Most common presenting muscle-related complaint Elevated muscle enzymes CK, aldolase, AST/ALT Myalgia Dermatologic findings of DM Gottron’s, Heliotrope, Other Other extramuscular features ILD, Arthritis, Dysphagia Most patients come to medical attention due to weakness consistent with myopathy. Most have elevated enzymes at presentation, but usually not the presenting feature. Similarly, Myalgia is less often the main symptom, but present in 50%. For some patients, skin manifestations are the presenting feature and may predominate. Some patients present with extramuscular manifestations.

Traditional PM/DM Criteria for Diagnosis: Weakness Symmetric proximal muscle weakness Enzymes Muscle enzymes elevated Electromyography Myopathy with normal nerve conduction Muscle Biopsy Inflammation Skin changes of DM Gottron’s papules, heliotrope, other

Traditional PM/DM Criteria for Diagnosis: Any 4 = Definite Any 3 = Probable Any 2 = Possible Exclusions: Family History Slow progression Other myopathies Weakness Enzymes EMG Muscle Biopsy Skin changes

Additional Diagnostic Considerations Magnetic Resonance Imaging Autoantibodies Evidence of inflammatory/rheumatic disease

Muscle Weakness in IIM Proximal, Symmetrical, Upper & lower Pelvic, shoulder girdles, neck flexors Dysphagia Respiratory involvement Subacute onset Muscle weakness vs Fatigue The muscle weakness of myositis is typical of myopathies. It generally involves skeletal muscle, more proximal than distal. Dysphagia can occur due to involvement of muscles of swallowing. Dysphagia and respiratory muscle involvement are risk factors for complications.

Muscle Weakness in IIM Signs of concern: Potential for Complication Dysphagia Respiratory Muscle Weakness Severe Weakness Can lead to aspiration pneumonia or respiratory failure.

Manual Muscle Testing Manual resistance against active contraction Rating scale of 1-5 Subjectivity Pain, Fatigue and Effort can confound

Activities to Assess Strength Timed stands from chair (arms folded) Squatting Sit from supine Stand on heels and toes Getting onto exam table. Timed 50-foot walk Lifting head off exam table

Laboratory Assessment of Muscle Injury Creatine Kinase Aldolase LDH AST/ALT Troponin Myoglobin Levels of enzymes and markers can vary with disease activity and thus can be used for assessing disease activity as well as for diagnosis. CK is most sensitive. The other markers are often used when CK is normal or not reflective of disease activity, or to support the significance of the CK result.

ELECTROMYOGRAPHY in Inflammatory Myopathy Myopathic Potentials Low Amplitude Short Duration Polyphasic Increased Spontaneous Activity Fibrillations, Positive Sharp Waves Increased Insertional Activity Normal Nerve Conduction

Electromyography Normal Polyphasic Myopathic Goetz: Textbook of Clinical Neurology, 2nd ed., Copyright © 2003 Elsevier Polyphasic Myopathic

Electromyography Resting Interference pattern Goetz: Textbook of Clinical Neurology, 2nd ed., © 2003 Elsevier