Neuromuscular

Benign Acute Childhood Myositis (BACM)


H&E stain
Necrosis: Regional, Early stage
  Large cluster of necrotic fibers (Arrows) with
    Cytoplasm: Dark or Very Pale
    Internal architecture & Myonuclei: Lost
  Perimysium near region of clustered necrosis
    Fragmented & Pale connective tissue
    Wide

VvG stain
Necrosis: Regional, Early stage
  Large cluster of necrotic fibers (Arrow) with
    Cytoplasm: Dark or Very Pale
    Internal architecture & Myonuclei: Lost
  Perimysium near region of clustered necrosis
    Fragmented & Pale connective tissue
    Wide

Gomori trichrome stain
Necrosis: Regional, Early stage
  Large region containing very pale necrotic fibers (Arrows)

NADH stain
Necrosis: Regional, Early stage
  Scattered fibers in region of necrosis have intermediate staining
Perimysial vein (Arrow): Pale staining wall

ATPase pH 4.3 stain
Necrosis: Regional, Early stage
  Histiocytes (Acid phosphatase +): Scattered in perimysium & endomysium
    In this early stage, and likely due to an ischemic nature of the process, there is no invasion of muscle fibers by histiocytes

Acid phosphatase stain
Necrosis: Regional, Early stage
  Perimysium: Only minor staining
  Muscle fibers: No staining around fibers in region of necrosis

Alkaline phosphatase stain
Necrosis: Regional, Early stage

COX stain
Mitochondrial stains: Many muscle fibers in region of necrosis stain pale for SDH and COX

SDH stain
Necrosis: Regional, Early stage
  Muscle fibers outside region of necrosis have increased MHC1 on their surfaces

MHC I stain

C5b-9 stain
Necrosis: Regional, Early stage
C5b-9
  Region of clustered necrosis (Above): Stains cytoplasm of many muscle fibers
    Necrotic muscle fibers
      Are mostly located near avascular perimysium
    Endomysial capillaries: Many stained for C5b-9
    Perimysial connective tissue: Diffusely stained for C5b-9
  Region with only scattered muscle fiber necrosis (Below)
    C5b-9 stains many endomysial capillaries
    Perimysial connective tissue: Some areas stained for C5b-9

C5b-9 stain

Gomori trichrome stain
Perimysial Vessels
  Surrounded by damaged perimysium populated by increased cellularity (probably histiocytes).

H&E stain

VvG stain
Perimysial Vessels
  Vessel walls are abnormal with loss of fibrils.

VvG stain

H&E stain
Necrotic muscle fibers
  Early necrotic fibers: Have "Dark" necrosis with dark stained featureless cytoplasm and no myonuclei
  Some non-necrotic fibers (Bottom Right) have retained sarcoplasmic reticulum staining in cytoplasm
  Later necrotic fibers: Pale, fragmented cytoplasm with no associated histiocytes

Gomori trichrome stain
Necrosis, Later stage
  Many Pale-stained fibers (Arrow) with: Fragmented cytoplasm; No associated histiocytes
  Scattered "Dark" Necrotic Fibers are also present

Gomori trichrome stain
Return to: BACM
See: RIIM
Return to: Neuromuscular Home Page

11/10/2022