Week 2 Inflammatory myopathies Flashcards
What is the clinical diagnostic criteria for inflammatory myopathies?
- proximal muscle weakness
- elevated muscle enzymes (enzymes leaked from damaged muscle cells): CK, aldolase, ALT, AST, LDH
- acute phase reactants freq. normal
- CK may be 2-100x normal - Myopathic EMG changes
- Muscle biopsy with inflammation
- Skin rash for DM
Describe polymyositis.
- insidious onset over several months, usually with systemic symptoms
- weakness of shoulder, pelvic girdle, neck muscles. 50% with pain and tenderness
- ocasional involvement of pharyngeal muscles
- pulmonary involvement: interstitial fibrosis
- cardiac involvement rare but can happen–see changes in EMG
Describe muscle biopsy results for polymyositis, Dermatomyositis, and inclusion body myositis.
- PM: classically muscle fibers in various stages of necrosis and regeneration. Endomysial, particularly CD8+ T cells. Muscles displaced with fibrous connective tissue and fat.
- DM: fiber invasion rare. Perivascular B lymphocytes (dominant) and CD4+ t cells
- perifasicular pattern of mononuclear cells - IBM: necrosis similar to PM. Perivascular infiltrates rare. Ragged red fibers, intracellular lined vacuoles, inclusion bodies, myeloid bodies
What are the findings in Dermatomyositis?
- PM findings + cutaneous changes
- Gottron’s papules: red scaly eruption of extensor surfaces of elbows/knees or mcps and digits
- heliotrophic discoloration of eyelids with or without periorbital edema
- shawl sign: rash on back of shoulders
- V sign: v line chest rash - Dermatomyositis without myositis
What are the findings in juvenile dermatomyositis?
Similar findings as adult DM but with: -vasculitis -calcification -lipodystrophy 2/3 will resolve by adulthood +/- calcinosis
What are autoantibodies seen in inflammatory myositis?
- Myositis specific autoantibodies:
- Anti Synthetases (Jo1, others):worse prognosis, pulmonary involvement may be seen. e.g. pulmonary fibrosis
- SRP (Signal Recognition particle): PM-severe muscle wkness, may have cardiac involvement
- Mi-2 (helicase components/histone complexes):dermatomyositis, milder course - myositis associated:
- Anti-Sm, Anti-RNP, Anti-Ro
- Anti-Scl70, Anti-PM-Scl, anti-U1RNP
What is antisynthetase syndrome?
- Inflammatory myositis with interstitial lung disease, Raynaud’s phenomenon, fever, mechanic’s hands (thin cracked skin on thumb and index fingers).
- associated with Usually Anti-Jo1 (anti-histidyl-tRNA synthetase)
Describe inclusion body myositis.
- up to 1/4 of inflammatory myopathies
- rare under 40, usually >50
- poor response to treatment, slower onset, 5-6 years
- proximal, distal, and can be asymmetric
- mildly elevated CPK
- pathologic findings on muscle biopsy: Sparse inflammation, mild fiber size variation, inclusion bodies, rimmed vacuoles, amyloid and filaments (EM) deposited in muscle. Often confused with PM.
What are causes of other myositis?
-Drugs: Cocaine, Heroin, alcohol, steroids,
-Infectious:
Viral: flu, parainfluenza, HIC, Coxsachie, CMV, adenovirus, others
Bacterial: pyomysitis, lyme
Fungal. Parasites: Trichinella
-Metabolic: Disorders of arbohydrate, lipid and purine metabolism
-Endocrine: Hypothyroidism, Cushing’s syndrome (or exogenous steroids)
-Rhabdomyolysis: Crush injury, seizures, exercise, alcohol
-Hereditary: Duchennes, males, x-linked. Severe . Becker’s. Similar but less severe.
What is the treatment for idiopathic inflammatory myopathy?
- corticosteroids are first line treatment
- followed by slow taper
- goal is normalization of muscle enzymes and increased strength - physical therapy
What is the prognosis for inflammatory myopathies?
- high 5 year survival >80%
- longer disease activity and treatment delay have worse outcome
- pharyngeal and lung involvement have poorer outcomes
- IBM has poorer prognosis
