B&b Week 5: Inflammatory Myopathies

Front 1

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Back 1

??

Front 2

4 histologic features of normal muscle

Back 2

1. polygonal fibers all about the same size
2. peripherally located nuclei
3. regular internal structure of the fibers
4. little to no connective tissue in between the fibers

Front 3

Neurogenic muscular atrophy
-Early sign/1st/round
-Interlude
-Late Sign/2nd round

Back 3

Early
-Initial partial denervation leads to angular atrophic fibers

Interlude
-Collateral reinnervation from remaining axons leads to fiber type alteration and subsequent grouping

Late
-Subsequent denervation leads to grouped type atrophy

Front 4

Destructive myopathy degeneration/regeneration steps
-24 hours
-48 hours
-72 hours
-4 days
-3 weeks successful regeneration
-3 weeks unsuccesful regeneration

Back 4

-24 hours: necrotic palor

-48 hours: myoblast and macrophage invasion

-72 hours: myoblast fusion

-4 days: basophilic regenerating fibers

-3 weeks successful regeneration: regenerated fibers with central nuclei

-3 weeks unsuccesful regeneration: atrophic denervated regenerated fiber

Front 5

Inflammatory myopathy histological characteristics
-Muscle fibers
-Inflammation

Back 5

-Muscle fiber degeneration(necrosis) and regeneration

-Inflammation can be perivascular, perimysial, or endomysial. Combined with pattern of muscle atrophy this dinstigues IM's from destructive myopathies like DMD.

Front 6

Polymyositis
-Age at manifestation
-Female:Male ratio
-Muscles affected
-Serum CK
-Muscle biopsy
-Pathogenesis

Back 6

>18 years
- 2:1
- proximal, symmetrical
- elevated up to 50x
- fiber necrosis and regeneration, perimysial and endomysial infiltrates with active myofiber invasion, CD8+ T cells
-T cell mediated disorder

Front 7

Dermatomyositis
-Age at manifestation
-Female:Male ratio
-Muscles affected
-Serum CK
-Other sign
-Muscle biopsy
-Pathogenesis

Back 7

-Any age, but peaks at 5-15 and 45-65
-2:1
-Normal to elevated (50X)
-RASH distinguishes it clinically from polymyositis
-Biopsy shows fiber necrosis and regeneration. Key feature is PERIFASICULAR ATROPHY +/- perivascular and perifascular infiltrate of B and CD4+ T cells
-Antibody mediated B cell vascular disorder-->ischemic injury.

Front 8

Inclusion body myositis
-Age at manifestation
-Female:Male ratio
-Muscles affected
-Serum CK
-Muscle biopsy
-Pathogenesis

Back 8

> 50 years

- 1:3 (so older men)

- distal to proximal, asymmetrical; unlike PM or DM

-Muscle fiber necrosis and degeneration. Inclusion bodies (rimmed vacuoles) in myofibers with prominent endomysial inflammation-->the hallmark of IBM

-Inflammatory process seconday to a yet unknown primary process. However, anti inflammatories don't work thus there is a poor outcome.

Front 9

Duchenne muscular dystrophy
-Age at manifestation
-Female:Male ratio
-Muscles affected
-Serum CK
-Other sign
-Muscle biopsy
-Pathogenesis

Back 9

- Onset by 2-4; wheelchair by 12, will be dead by 30's
- boys only??
- Proximal progressive weakness; pseudohyperotrophy
- elevated CK
- complications of cardiomyopathy, respiratory insufficiency, and scoliosis
- Biopsy shows total absence of dystrophin, necrotic muscle fibers with infiltrate ONLY IN THE FIBERS (unlike IM's), lots of small regenerating fibers. In late stage DMD, there will be a lot of fibrosis (cause of the pseudohypertrophy) and atrophic fibers.
-Caused by mutations in dystrophin, usually from deletions of one or more exons. 30% of mutations are de-novo with no family history. Essentially a sarcoplasmic membrane dysfunction.