7. Proximal muscle weakness
Shoulders, thighs, trunk and pelvic girdle
muscles are most affected.
Never facial and ocular muscles
Esophagus, pharynx and respiratory
muscles may involved.
May arthralgia and myalgia
21. Lab
Muscle enzyme–
Creatine Kinase
Indicator of disease activity and severity
May be normal in very early, remission or
atrophy pts.
CK rise weeks preceding clinical evidence of
muscle weakness
Other muscle enzymes: ALT, AST, LDH,
aldolase
22. Autoantibodies
ANA, anti-nuclear antibody ~80%
Anti-ENA, extractable nuclear antigen
Anti-Jo-1
• most common myositis-specific autoantibody ~30%.
• anti–tRNA synthetase syndrome: Lung iinvolvement, Raynaud's
phenomenon
Anti-SRP antibodies
• signal recognition particle (SRP) : translocation of newly
synthesized proteins into the endoplasmic reticulum.
• only in polymyositis with severe myopathy and aggressive
disease
Anti-Mi-2 antibodies
•
•
directed against a helicase involved in transcriptional activation
associated with the relatively acute onset of classic
dermatomyositis with erythroderma and the shawl sign
23.
24. EMG of PM/DM
•
Triads in 40% of pts:
polyphasic, small
amplitude, short
duration
•
Chracteristic but not
diagnostic
•
15% of pts may be
normal EMG
25. Muscle biopsy of polymyositis
•Focal and endomysial
infiltration of T cell, esp.
CD8, with small number
of macrophage
•Muscle fiber
degeneration and
atrophy
26. Muscle biopsy of dermatomyositis
Peri-vascular
infiltration of
inflammatory cells,
composed of
higher percentage
of B cell and CD4
T cells.
33. Myositis in autoimmune diseases
Common in scleroderma, SLE, MCTD,
Sjogren’s syndrome
Sometimes in RA, Adult Still’s disease,
Vasculitis syndrome. Esp. Wegner’s
granulomatosis and polyarteritis nodosa.
34. Myositis association with malignancy
Frequency of malignancy in myositis
derived from 5%-35%
Most common sites: NPC, Lung, GI, Gyn
Work-up: careful history and PE and
routine laboratory, tumor markers, image
studies
36. Management of PM/DM
Corticosteroid alone (60-100 mg/day)
Immunosuppressive agents in
conjunction with corticosteroid
therapy
Hydroxychloroquine (100-200 mg/day)
Azathioprine (2 mg/kg/d-50 mg/d)
Methotrexate (MTX 7.5-25 mg/wk)
Cyclphosphamide (50-200mg/d)
Cyclosporin A (7.5-10mg/kg/d)
37. Steroid in Myositis
prednisolone1-2 mg/kg/day or
methylprednisolone pulse therapy
90% improved after steroid therapy in
weeks to months
50-75% had complete remission
Need slowly tapering of steroid
Tends to occur when taper steroid
40. Conclusions
Workup of muscle weakness
Differential diagnosis of myopathy
Classification and diagnostic criteria of
dermatomyositis and polymyositis
Has specific autoantibodies
Can be controlled by steroid and steroidsparing agents
