Neuromuscular

Mi-2 antibodies: α & β

85 yo female with 1 year of progressive dysphagia, & symmetric weakness, proximal legs & arms + distal arms with 50 lb weight loss.
CK = 2,800.
Inflammatory Myopathy
  Muscle fibers
    Morphology: Varied sizes; Many small
    Internal architecture
    Cytoplasm
    Immune: MHC1 upregulated
  Inflammation
    Types
      Lymphocytes: Foci & Scattered in Endomysium, Types
      Histiocytes: Scattered in Endomysium; Few in Perimysium
    Distribution: Endomysial; Foci & Scattered
    Cell Foci contain: Small vessels that contain endothelium & thin wall
  Connective tissue
    Perimysium: Fragmented in some regions
    Endomysium: Increased; C5b9 deposition
  Vessels
    Endomysial capillaries: Large; Reduced numbers; Alkaline phosphatase +

H&E stain
Muscle fibers
  Sizes: Varied; General atrophy
Inflammation
  Scattered in endomysium & perimysium
  Lymphocyte Foci
Endomysial connective tissue
  Increased between muscle fibers

Congo red stain

H&E stain
Inflammation
  Scattered in endomysium betweem muscle fibers
Perimysial connective tissue: Fragmented

VvG stain

Congo red stain
Lymphocyte cell foci
  Often contain smaller vessel with thin wall

Congo red stain

H&E stain

CD4 stain
Lymphocyte cell foci
  Often contain CD4 cells

CD4 stain

CD8 stain
Lymphocyte cell foci
  CD8 cells
    Scattered within foci and in endomysium
    Form small clusters

CD8 stain

CD8 stain

CD20 stain
Lymphocyte cell foci
  CD20 cells
    Scattered in endomysium
    Form small clusters in perimysium

CD20 stain
Histiocytes

Acid phosphatase stain
Acid phosphatase+ histiocytes are
  Scattered in: Endomysium & Perimysium
  Associated with damaged muscle fibers

Acid phosphatase stain
Esterase+ histiocytes are
  Scattered in: Endomysium & Perimysium

Esterase stain

CD163 stain
CD163+ histiocytes are
  Scattered in: Endomysium & Perimysium

CD163 stain

HAM56 stain
HAM56+ histiocytes are
  Scattered in: Endomysium & Perimysium

HAM56 stain

HAM56 stain

MxA stain
MxA stains
  Endomysial cells
  Muscle fiber cytoplasm: Scattered very small fibers

MxA stain

MxA stain
Capillary pathology

Alkaline phosphatase stain
Endomysial Capillaries
  Increased staining by alkaline phosphatase
Muscle fibers
  Cytoplasm of scattered very small, immature muscle fibers is stained by alkaline phosphatase

Alkaline phosphatase stain
Endomysial Capillaries
  Size: Large
  Number: Reduced; Scattered muscle fibers with no adjacent capillary

UEA1 stain

C5b-9 stain
C5b-9 stains
  Endomysial connective tissue
  Cytoplasm of rare necrotic muscle fiber (Below; Arrow)

C5b-9 stain

C5b-9 stain
Endomysial Connective Tissue
  Increased between muscle fibers
  Stains for decorin

Decorin stain

VvG stain
Muscle fibers
  Sizes: Varied
  MHC1: Difffusely upregulated by muscle fibers (Below)

MHC1 stain

MHC1 stain
Muscle fibers
  Sizes: Varied
  MHC1: Difffusely upregulated by muscle fibers (Below)
Inflammation
  Many MHC1+ cells in endomysium & perimysium

MHC1 stain
Muscle Fibers

ATPase pH 9.4 stain
Muscle Fiber Types
  No grouping
  Many immature, intermediate-stained 2C fibers (Below)
  Few pale type 2A Fibers (Below)

ATPase pH 4.3 stain

LC3 stain
Muscle Fibers: LC3 aggregates
  Present in muscle fibers in some regins of muscle
  LC3 in muscle fibers: Multiple punctate aggregates scattered through cytoplasm, or clustered in some regions

LC3 stain

LC3 stain
Muscle Fiber Internal Architecture
  Coarse & Immature

NADH stain

COX stain
Muscle Fiber Internal Architecture
  No definite mitochondrial pathology
  COX stain is present in all muscle fibers
  SDH stain is increased in some small fibers, possibly related to immaturity

SDH stain
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1/21/2025