Neuromuscular

IMMUNE MYOPATHIES WITH PERIMYSIAL PATHOLOGY (IMPP)

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


IMPP: General

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

Pathology
  Perimysial damage: Prominent
  Probably same as: Dermatomyositis: Adult variant

Comparison: IMPP vs. Dermatomyositis + Vascular pathology (DM-VP)
  Pathology: Both IMPP and DM-VP have
    Muscle fiber pathology that is most prominent at the edge of fascicles
    Immune myopathy
  Skin rash: 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
 Near perifascicular path

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


Normal
Absent 
Absent

Normal
Absent 
Absent


Large
Few 
Common

Absent
Common 
Absent


IMPP Muscle Pathology



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 be normal (Bottom left) or show


H&E stain

Perimysial inflammation

Acid phosphatase

Perimysial cells: Acid phosphatase positive

Acid phosphatase

Perimysial cells: Acid phosphatase positive


Esterase

Perimysial inflammation
Esterase positive macrophages

Acid phosphatase stain

CD-68 positive cells in perimysium
  and endomysium



Alkaline phosphatase stain

Alkaline phosphatase staining of perimysium


H&E stain

Perifascicular myopathy & atrophy
Regeneration & Necrosis of perifascicular fibers

Immunocytochemistry

N-CAM positive atrophic muscle fibers
 

Immunocytochemistry

MHC Class 1 positive muscle fibers
Positive fibers are perifascicular and have normal size
A similar pattern may occur in mild dermatomyositis

Return to Inflammatory myopathies
Return to Jo-1 myositis

12/14/2011