Immune Myopathies: MDA5 antibody-associated
Myopathologic features
1,2
Perimysium
Macrophages: Scattered perimysial & endomysial; Some perivascular
Muscle fibers
Necrosis & Regeneration: Few fibers; Scattered
MHC Class I: Upregulated in some patients
LC3 aggregates
NOS2, HSP70, NCAM in sarcoplasm, especially in perifascicular fibers near inflammation
Interferon-related molecules: RIG-I; ISG15
Capillaries
Normal or Mildly reduced numbers
![](../pics/biopsy/inflammation/mda5/mda5help.jpg)
H&E stain
|
Fiber size: Varied
Necrosis & Regeneration: Scattered
![](../pics/biopsy/inflammation/mda5/mda5hehp.jpg)
H&E stain
|
![](../pics/biopsy/inflammation/mda5/mda5gthp.jpg)
Gomori trichrome stain
|
Aggregates: Central; Irregular shapes
![](../pics/biopsy/inflammation/mda5/mda5acp.jpg)
Acid phosphatase stain
|
Necrosis & Regeneration: Cells
Scattered in endomysium
Replacing necrotic muscle fibers
![](../pics/biopsy/inflammation/mda5/mda5est.jpg)
Esterase stain
|
![](../pics/biopsy/inflammation/mda5/mda5atp43.jpg)
ATPase pH 4.3 stain
|
Type 2 muscle fiber predominance
![](../pics/biopsy/inflammation/mda5/mda5nadh.jpg)
NADH stain
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Internal architecture: Linearized in type 2 muscle fibers
![](../pics/biopsy/inflammation/mda5/mda5lc3b.jpg)
LC3 stain
|
Aggregates: Punctate; Clustered
![](../pics/biopsy/inflammation/mda5/mda5lc3a.jpg)
LC3 stain
|
![](../pics/biopsy/inflammation/mda5/mda5mhc1lp.jpg)
MHC Class I stain
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MHC Class I: Upregulated on all muscle fibers
![](../pics/biopsy/inflammation/mda5/mda5mhc1hp.jpg)
MHC Class I stain
|
![](../pics/biopsy/inflammation/mda5/mda5ulex.jpg)
Ulex stain
|
Capillaries: Corkscrew shape
Return to
Inflammatory myopathies
Return to
IMPP
Return to
Pathology index
Return to
MDA5
References
1.
Curr Opin Rheumatol 2011;23:595-604
2.
Am J Pathol 2016;186:691-700
9/24/2019