Neuromuscular

NXP-2 Antibody: Myopathy Patterns

NXP-2 Myopathology Patterns: 3 types
  Regional Necrosis
    Regional Ischemic Immune Myopathy (RIIM)
      Other RIIM pathology
  Perifascicular Myopathy
    Dermatomyositis with Vascular Pathology (DM-VP)
  Minimal Myopathy with Capillary Pathology (MMCP)

Regional Ischemic Immune Myopathy (RIIM): NXP-2 Antobody-associated

Clusters of Necrotic & Regenerating Muscle Fibers
  Necrosis: Fibers in each cluster are in similar stages of necrosis or regeneration
  Anatomy: Clusters of damaged muscle fibers may not be at the very edge of fascicles
Perimysial Connective Tissue
  Wide
  Fragmented
  No immune cells

H & E stain

Congo red stain
Necrotic Muscle Fibers: Small cluster
  Necrotic fibers often have moderately dark, featureless cytoplasm with no visible myonuclei

C5b-9 complement stain
Necrotic Muscle Fibers
  Muscle fiber features
    C5b-9 staining of muscle fiber cytoplasm: diffuse
    NADH staining of cytoplasm is absent
  Anatomy
    Necrotic fibers are in clusters

NADH stain

NADH stain
Neighboring clusters: Necrotic (Left) & Regenerating (Right) Muscle fibers

Esterase stain

VvG stain
Neighboring clusters: Necrotic (Left) & Regenerating (Right) Muscle fibers

ATPase pH 9.4 stain

Alkaline phospohatase stain
Neighboring clusters: Necrotic (Above) & Regenerating (Below) Muscle fibers

ATPase pH 9.4 stain

Acid phosphatase stain

VvG stain
Clusters of Necrotic & Regenerating Muscle fibers: Distant from vascular bundle (Lower right)
Vessels
  Artery, Large (Left): Normal structure
  Artery, Small (Center): Abnormal wall structure
    Fibril (Elastin) layer: Incomplete (White arrow)
    Connective tissue inside fibril layer
  Vein (Right; White arrow)     Pale wall inside fibril layer
    No visible lumen

VvG stain

Minimal Myopathy with Capillary Pathology: NXP-2 Antibody-associated

Features
  Muscle
    Fiber morphology: Lipid droplets present in some fibers
    Fiber sizes: Varied
    MHC Class I stain: Increased on muscle fiber surfaces
  Capillaries
    C5b-9 staining
    Sizes: Mildly large

H&E stain
NXP-2: Minimal myopathy
  Muscle fibers
    Sizes: Moderate variation
    No necrosis or immaturity
  Endomysial connective tissue: Normal

H&E stain

Gomori trichrome stain
NXP-2: Minimal myopathy
  Muscle fibers
    Sizes: Moderate variation
    Smaller fibers are dark on PAS stain
    No necrosis or immaturity
  Endomysial connective tissue: Normal

PAS stain

H&E stain
NXP-2: Minimal myopathy
  Muscle fibers
    Sizes: Moderate variation
    No necrosis or immaturity
  Endomysial connective tissue: Normal

Gomori trichrome stain
NXP-2: Minimal myopathy
  Muscle fibers
    Sizes: Moderate variation
    No necrosis or immaturity
  Endomysial connective tissue: Normal
  Endomysial capillaries: Normal to Slightly large (Arrow)

Gomori trichrome stain

Congo red stain
NXP-2: Minimal myopathy
  Muscle fibers
    Sizes: Moderate variation
    No necrosis or immaturity
  Endomysial connective tissue: Normal
  Endomysial capillaries: Normal to Slightly large (Arrow)

Congo red stain

ATPase pH 9.4 stain
NXP-2: Minimal myopathy
  Muscle fibers
    Lipid droplets in type 2 (Dark) fibers
    Type 2 fiber predominance

ATPase pH 4.3 stain
NXP-2: Minimal myopathy
  Muscle fibers
    Type 2 fiber predominance

Sudan black stain
NXP-2: Minimal myopathy
  Muscle fibers
    Lipid droplets more prominent in type 2 (Pale) fibers

Sudan black stain

Sudan black stain

MHC Class I stain
NXP-2: Minimal myopathy
  Muscle fibers: MHC I abnormally expressed on the surface of most fibers

MHC Class I stain
NXP-2: Minimal myopathy
  Muscle fibers: MHC I abnormally expressed on the surface of most fibers

MHC Class I stain

Esterase stain
NXP-2: Minimal myopathy
  Esterase stains some endomysial capillaries

Acid phosphatase stain
NXP-2: Minimal myopathy
  No prominent staining of endomysial capillaries with Acid or Alkaline phosphatase

Alkaline phosphatase stain

NADH stain
NXP-2: Minimal myopathy
  NADH stains some endomysial capillaries

UEA I stain
NXP-2: Minimal myopathy
  UEA I normally stains endomysial capillaries
  Some small muscle fibers have no adjacent capillary (Arrows)

UEA I stain

Decorin stain
NXP-2: Minimal myopathy
  Endomysial capillaries are midly large

Decorin stain
NXP-2: Minimal myopathy
  Endomysial capillaries are midly large (Arrow)

Decorin stain

C5b-9 stain
NXP-2: Minimal myopathy
  C5b-9 is stained on many endomysial capillaries

C5b-9 stain

C5b-9 stain
NXP-2: Minimal myopathy
  C5b-9 is stained on many endomysial capillaries
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11/28/2022