diagnostics & etc

Dermatomyositis (Diagnostics)

CK

• usually elevated, but maybe normal

Dermatomyositis (Diagnostics)

EMG

• inc insertional activity, fibrillation potentials, positive sharp waves, short duration low amplitude motor units

Dermatomyositis (Diagnostics)

Muscle biopsy

• deposition of the complement membrane attack complex around small blood vessels 🡪 highly sensitive and specific for dermatomyositis. 

Dermatomyositis (Pharmacology)

• If assoc with malignancy, tx of cancer may improve weakness

• Corticosteroids 🡪 first line of therapy 

Polymyositis (Diagnostics)

CK

• elevated in cases of active polymyositis, marker for tx purpose

Polymyositis (Diagnostics)

EMG

•  increased insertional activity, fibrillation potentials, positive sharp waves, and short-duration low-amplitude motor units

Polymyositis (Diagnostics)

Muscle biopsy

• characteristic findings such as partial invasion of non necrotic muscle fibers with activated macrophages and CD8+ cytotoxic T cells 

Polymyositis (Pharmacology)

• Pharmacologic Mx:

  • Corticosteroids 🡪 first line of therapy 

Inclusion Body Myositis (Diagnostics)

CK

•  elevated but typically not exceeding 12 times the upper limit of normal

Inclusion Body Myositis (Diagnostics)

EMG

• increased insertional activity and short-duration polyphasic motor units

Inclusion Body Myositis (Diagnostics)

NCS

•  finding consistent with neuropathy

Inclusion Body Myositis (Diagnostics)

Functional decline

often slow

Inclusion Body Myositis (Diagnostics)

Muscle biopsy

• rimmed vacuoles, cytoplasmic inclusions, and mononuclear cell invasion in endomysial fibers

Inclusion Body Myositis (Pharmacology)

None

Dystrophinopathies (Diagnostics)

CK

• elevated >100x N for B DMD and BMD

Dystrophinopathies (Diagnostics)

AST AND ALT

• maybe elevated, work-up to prevent unnecessary liver biopsy

Dystrophinopathies (Diagnostics)

Blood test

• Dystrophin gene testing mutation

Dystrophinopathies (Diagnostics)

Muscle biopsy

•  if (-) gene mutation, but presence of clinical findings of dystrophinopathy

Dystrophinopathies (Diagnostics)

Immunocytochemistry & immunoblotting

• determine the presence, quantity, & molecular size of dystrophin

Dystrophinopathies (Diagnostics)

EMG

no longer indcated

Duchenne Muscular Dystrophy (Pharmacology)

• Corticosteroids 🡪 improves strength and slow functional decline

• Observe preservation of ambulation up to 3 years with prednisone or deflazacort

• Timing of corticosteroid initiation impt. 🡪 d/t inc. risk of obesity, behavior changes, immune suppression, cataracts, and bone demineralization

Becker Muscular Dystrophy (Diagnostic)

None

Becker Muscular Dystrophy (Pharmaology)

None