Muscle fiber necrosis
  Other changes
Immune changes
  Cell types
  Vessels in cell foci

BCIM: Lymphocytic inflammation around vessels in perimysium

Perivascular inflammation
  Cell type: Lymphocytic
  Location: Perimysium
Myopathic changes
  Fiber size: Varied
  Endomysial connective tissue: Variably increased

H&E stain

GT stain

Perivascular lymphocyte inflammation in perimysium
  Surrounds & contains intermediate-sized vessels: No elastin fibrils in their wall.

Endothelial cells in vessel: Large; May be Esterase+


BCIM: Cell types in perivascular inflammation

H&E stain
Small dark cells with little cytoplasm surround an intermediate sized vessel

CD20 stain
CD20+ B-cells are a prominent component of some perivascular inflammatory foci.

CD4 stain

CD20 stain
CD4 T-lymphocytes in
  endomysial connective tissue

CD20 B-lymphocytes in
  perimysium extending into endomysium

CD4 stain
CD4 T-lymphocytes
  Present in perimysium, extending into endomysium

CD20 stain
CD20 B-lymphocytes
  Present in subset of inflammatory foci
Serial sections: B-cell foci are present in some but not all (arrow) regions of CD4 cellularity

CD3 stain
A minority of the perivascular cells stain for CD3 (T-cells)

CD68 stain
CD68+ macrophages are scattered through the infiltrate and in neighboring connective tissue

Acid phosphatase stain
Acid phosphatease positive histiocytic cells are scattered through the perivascular infiltrate

Inflammatory foci contain vessels

CD31 stain
CD31+ endothelial cells are present in
  Small vessels within perivascular inflammatory foci
  Lumen of intermediate-sized vessel
Vessels stain for ATPase (Below)

ATPase pH 4.3 stain

Esterase stain
Intermediate-sized vessels in inflammatory foci
  Endothelial cells are large (Below) & stain for esterase (Above, arrows)

VvG stain

BCIM: Complement Deposition (C5b-9; MAC)

C5b-9 stain

C5b-9 stain
BCIM muscle: C5b-9 components of complement
  are deposited in endomysial connective tissue
Control muscle: No C5b-9 components of complement
  are deposited in muscle

C5b-9 deposits: Endomysium & Necrotic muscle fiber cytoplasm

C5b-9 stain

Brachio-Cervial Inflammatory Myopathy: Myopathic changes

Muscle fiber necrosis

H&E stain
Muscle fibers in varied stages of necrosis & regeneration

H&E stain
Early necrosis: Dark muscle fiber with loss of cytoplasmic structure

H&E stain
Later stage of necrosis: Muscle fiber invaded by cells with large nuclei and abundant foamy cytoplasm

H&E stain
Later stage of necrosis: Collapsed muscle fiber largely replaced by cells

CD68 stain
Muscle fiber necrosis with CD68+ histiocytic cellularity invading fiber

CD68 stain
Segmental muscle fiber necrosis with CD68+ histiocytic cellularity

CD68 stain
Muscle fiber necrosis with CD68+ histiocytic cellularity replacing part of a fiber

BCIM: Varied muscle fiber size

ATPase pH 9.4 stain
Varied fiber size: Type 1 & Type 2 fibers are small and large.

ATPase pH 4.3 stain
Many muscle fibers are type 2C with varying degrees of intermediate staining.

MHC Class I
  Upregulation on muscle fibers, especially surface
  Expressed on cells in inflammatory foci

MHC Class I stain

BCIM: Regeneration

H&E stain

ATPase pH4.3 stain
Basophilic regenerating muscle fiber Numerous Type 2C immature or regenerating muscle fibers

H&E stain

Basophilic regenerating muscle fiber: Contains bluish cytoplasm & large nuclei

BCIM: Myopathic changes with varied muscle fiber size

H&E stain

H&E stain
Chronic myopathy
Varied fiber size: Small muscle fibers are rounded
Scattered muscle fibers with internal nuclei
Increased endomysial connective tissue, mild
Muscle fiber damage: Necrosis (Right) & Focal invasion (Below)

BCIM: Focal invasion of muscle fibers by mononuclear cells

Acid phosphatase stain

CD4 stain
Focal invasion of muscle fibers

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