Neuromuscular

Immune Myopathies with Perimysial Pathology (IMPP) 1

Clinical syndromes
  Dermatomyositis: Adult (variant) type
  Graft-vs-Host
  Myopathies with
    Anti-Jo-1 Antibodies
    Other tRNA synthetase antibodies
    High Aldolase & Normal CK
    Minocycline
Dermatomyositis vs IMPP
IMPP muscle pathology
  Dermatomyositis: Adult-onset IMPP
  Jo-1 antibody + pathology
  PL-12 antibody + pathology


IMPP: General

Clinical Features
  Immune myopathies: Similar to Jo-1 & tRNA synthetase antibody related immune myupathies

Pathology
  Perimysial damage: Prominent

COMPARISON: IMPP vs. Dermatomyositis + Vascular pathology (DM-VP)

  COMMON FEATURES: Both IMPP and DM-VP have
  Pathology
    Muscle fiber pathology: Most prominent at the edge of fascicles
    Immune myopathy with connective tissue pathology
  Clinical
    Skin rash: DM-VP & Some IMPP
    Myopathy: DM-VP & Some IMPP

  DISTINCTIVE DIFFERENCES between the syndromes
IMPP Dermatomyositis +
  Vascular pathology
CLINICAL Age range Adult Child or Adult
Skin Raynaud's
Mechanic's hands
Heliotrope rash
Interstitial lung disease Common Uncommon
Myalgias Common Occasional
ANTIBODY Myositis-associated Jo-1
tRNA synthetase
Mi-2
p140; p155
MUSCLE
  PATHOLOGY
Focal inflammation
  Location
  Type
 

Perimysium
Macrophage-like

 

Perivascular,
Mononuclear cells
Often with CD20 cells
Perimysium pathology
  Fragmentation
  Cellularity
  Without myopathy
  Alkaline phophatase staining

Common
Macrophage-like
Some patients
Some patients

Occasional
Mononuclear
Never
Unusual
Perifascicular muscle fibers
  COX staining reduced
  Necrosis & Regeneration
  Internal architecture
  Caveolin-3 aggregates

Never
Common
Regeneration
Rare

Most patients
Unusual
Vacuoles & Aggregates
Common
Capillaries: Different regions
 Near perifascicular pathology

  Ulex staining
  C5b-9 deposition
  Alkaline phophatase staining
 Amid perifascicular pathology
  Ulex staining
  C5b-9 deposition
  Alkaline phophatase staining


Normal
Absent 
Absent

Normal
Absent 
Absent


Large
Few 
Common

Absent
Common 
Absent


IMPP Muscle Pathology (Jo-1 antibody positive)


H&E stain

Perimysial fragmentation
  • The perimysium is loculated with many focal clear areas
  • Cells in the perimysium are most frequently macrophages. Features include
  • Adjacent muscle fibers may show


H&E stain

Perifascicular myopathy & atrophy
Regeneration & Necrosis of perifascicular fibers

NCAM stain

N-CAM positive atrophic muscle fibers
 



H&E stain
Perimysium with:
  Damaged structure (Irregular, Pale regions)
  Cellularity: Large cells with cytoplasm & large nuclei
Neighboring myopathology:
  Muscle fibers: Necrotic & Regenerating (Small, Basophilic)

Gomori trichrome stain

VvG stain

Perimysial Inflammation


H&E stain

Cells in perimysium

Esterase

Esterase positive macrophages

CD68 stain

CD-68 positive cells in perimysium
  and endomysium


Esterase
Perimysium: Esterase positive macrophages


Acid phosphatase

Acid phosphatase
Acid phosphatase positive cells: Predominantly in Perimysium; Scattered in endomysium

Acid phosphatase


Alkaline phosphatase stain
Alkaline phosphatase staining
  Perimysium
  Extends into endomysium
  Muscle fiber cytoplasm (Smaller, immature fibers)

Alkaline phosphatase stain


MHC-I stain

MHC Class 1 staining
Positive muscle fibers are
  Perifascicular (Above), or
  Diffuse (Right)
  Have Similar patterns in
    DM + Vascular Pathology
Perimysial cells also stain (Below)

MHC-I stain

MHC-I stain

Return to Inflammatory myopathies
Return to Jo-1 myositis

References
1. Curr Opin Rheumatol 2011;23:595-604

3/17/2014