Myopathies

 

Juvenile Dermatomyositis

- Autoimmune activity against endothelial cells of small vessels.

 

Pathology:

- perifascicular atrophy

- basophilia

- myofibrillar rarefaction

- decreased capillary density

- membrane attack complex activity

 

Treatment:

- ABCs (resp monitoring, PFTs, swallowing, cardiac consult)

- PT (risk for contractures)

- Corticosteroids

            - IV Solumedrol 30mg/kg/day if presumed GI malabsorption

            - Prednisone PO 2 mg/kg x 6 months

            - Vit D, dietary counselling, Ca, bone density monitoring

            - Methotrexate (PO or IM)

            - IVIG used sparingly but can be helpful

 

20% recurrence risk

 

Adult dermatomyositis (differences)

- more defined pain

- Reynaud's phenomenon

- systemic symptoms

- underlying malignancy esp. Ovarian but highest in males >60

- first line tx is corticosteroids and IVIG

- second line is azathioprine, methotrexate, cyclophosphamide, MMF

 

Polymyositis

- can be painless

- immune cells attack muscle (T-cells)

- 70% response to treatment

 

IBM (inclusion body myositis)

- inflammatory, there is a hereditary form with quad sparing

- weakness of finger and wrist flexors and ankle dorsiflexion (distal muscles, as opposed to proximal muscles in other dx)

- disease of older people, not associated with malignancy

- pathological similarities to Alzheimer's

- invasion of muscle fibers, vacuoles, amyloid inclusion bodies (fluo stains)

- overall treatment ineffective

 

Focal nodular myositis

- single muscle group

- painless, mild weakness, florrid inflammation

- usually not treated unless weak

- not usually have cause, sometimes from injections/immunizations

 

Vasculitis

- can cause muscle pain from flrrid vasculitis

 

Eosinophilic myositis

- rare, very painful

- multiple causes from peripheral eosinophilia, e.g., parasitic infections