Transcript Inflammatory Myopathies

Inflammatory Myopathies
Katie DePlatchett, M.D.
AM Report
May 26, 2010
Infammatory Myopathies
 Polymyositis
 Dermatomyositis
 Inclusion body myositis
 Overlap myositis – related to connective tissue
disorder
 Cancer-associated myositis
 myositis with clinical paraneoplastic features and
without an overlap autoantibody
Polymyositis
 Symmetric proximal muscle weakness
 Elevated serum muscle enzymes*
 CK, CK-MB, AST, ALT, LD, Aldolase
 Myopathic changes on EMG
 Muscle biopsy
 cellular infiltrate is predominantly within the fascicle with
inflammatory cells invading individual muscle fibers
 cell–mediated, increased numbers of cytotoxic CD8+ T cells,
which appear to recognize an antigen on the muscle fiber surface
Polymyositis - histopathology
Dermatomyositis
 Symmetric proximal muscle weakness
 Elevated serum muscle enzymes
 Myopathic changes on EMG
 Muscle biopsy
 humorally–mediated disorder (CD4 cells), cellular infiltrate,
located principally in perifascicular regions, focused around
blood vessels
 Rash
Dermatomyositis - histology
Dermatomyositis – skin findings
 Gottron’s sign
 Heliotrope rash
 Shaw sign & V sign
 Mechanic’s hands
 Psoriasiform changes in scalp
What about auto-antibodies???
 ANA present in up to 80% of
 myositis-specific autoantibodies:
 anti-Jo-1, highly specific, associated w/ ILD
 anti-SRP antibodies
 antibodies to Mi-2, (a nuclear helicase)
 Not diagnostic but affects prognosis
Inclusion body myositis
 insidious onset
 more prominent distal muscle weakness &
atrophy (wrists, fingers, anterior tibial)
 Asymmetric muscle involvement
 On average, serum muscle enzyme levels are
lower in IBM than in PM
 presence of typical inclusion bodies on muscle
biopsy
Overlap Myositis
 Myopathy associated with the other connective
tissue diseases
 scleroderma, systemic lupus erythematosus, mixed
connective tissue disease
varies from clinically insignificant to typically
severe PM or DM in which myopathy dominates
the clinical picture
 anti-Ro, anti-La, anti-Sm, or antiribonucleoprotein (RNP) antibodies.

Differential Diagnosis
 Drug induced: statins, colchicine,
hydroxychloroquine, steroids, etoh, cocaine
 HIV
 ALS
 Myasthenia gravis
 Muscular dystrophies
 Inherited metabolic myopathies
 Amyloid & Sarcoid myopathies
Work-up
 Serology: CK, CK-MB, AST, ALT, adolase, ANA,
anti-Jo1, anti-SRP, anti-Sm, anti-Ro
 Utox, HIV
 Muscle biopsy
 +/- EMGs
 Age appropriate cancer screening for those with
dermatomyositis
Treatment
 Steroids, PT/rehab
 Minimal data of long-term follow-up of pts
 PM: 50% were refractory to steroids
 DM, 87% responded to steroids but 92% flared when
therapy was tapered.
 Overlap myositis: 89 to 100% responded to steroids,
depended on specific antibodies.
 Methotrexate or Azathioprine
Prognosis
 Determinants of prognosis:
 the specific type of myositis
 disease severity
 delay in diagnosis
 Certain autoantibody profile
 PM: least likely to respond to steroids
 Overlap myositis: most likely to respond to
steroids.