Muscle fiber necrosis
  Other changes
Immune changes
  Cell types

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
Varied fiber size: Type 1 & Type 2 fibers are small and large.

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

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

BCIM: Inflammation around vessels in perimysium

H&E stain

GT stain
Perivascular inflammation with myopathic changes, including varied fiber size and increased endomysial connective tissue,

Mononuclear cell inflammation typically surrounds intermediate-sized perimysial vessels with no elastin fibrils in their wall.



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.

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

CD31 stain
CD31+ endothelial cells are present in small vessels within the perivascular inflammatory focus and in the lumen of the intermediate-sized vessel

Esterase stain
Endothelial cells in intermediate-sized vessels are enlarged & stain for esterase (arrows)

BCIM: Other inflammatory cells

CD4 stain

CD20 stain
CD4 positive mononuclear cells in
  endomysial connective tissue

CD20 positive B-cells in perimysium & endomysium

CD4 stain

CD4 positive mononuclear cells present in endomysium & perimysium

CD20 stain

CD20 positive B-cells present in focal regions
Serial sections: B-cell foci are present in some but not all (arrow) regions of CD4 cellularity

BCIM: Complement Deposition (C5b-9; MAC)

C5b-9 stain

C5b-9 stain
BCIM muscle: CD5b-9 components of complement
  are deposited in endomysial connective tissue
Control muscle: No CD5b-9 components of complement
  are deposited in muscle

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