Immune Myopathies with Perimysial Pathology (IMPP): PL-12 antibody associated

Also see
  Dermatomyositis: Adult, IMPP type
  Jo-1 muscle pathology

H&E stain

Perimysial cellularity
  • Cells in the perimysium are histiocytic (Above; Arrow). Features include
    • Large nuclei
    • Prominent cytoplasm
    • Staining for Acid Phosphatase, Esterase and CD-68
  • Fiber size (Below)
    • Perifascicular fibers: May be small
    • Other fibers: Varied sizes, Intermediate or Normal

Acid phosphatase stain

Perimysial cells: Acid phosphatase positive

Acid phosphatase

CD4 stain
CD4+ cells: Perimysial, & Scattered endomysial

MHC Class I
Perifascicular muscle fibers: Express MHC Class I

MHC Class I

C5b-9 deposition on Perimysium

C5b-9 stain

Varied fiber size: Some small fibers are type 2C

ATPase pH 4.3 stain

Return to Inflammatory myopathies
Return to IMPP

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