FSH: Adult

H&E stain

H&E stain

H&E stain
Varied muscle fiber size: Atrophy & Hypertrophy
Regenerating (Basophilic) muscle fibers
Endomysial connective tissue: Moderately increased
Inflammation: Around smaller, intermediate sized vessels, not arteries or veins

VvG stain
Perivascular inflammation (Above)
    Around small perimysial vessels with no elastin in their wall (Above)
    Not usually around arteries or veins (Below)
  Cell types: Mononuclear, Especially CD4 & CD8

VvG stain

H&E stain

H&E stain

Acid phosphatase stain
Necrotic muscle fibers: Scattered; More common in muscles with less fibrosis

Congo red stain

ATPase, pH 4.3 stain
Small & large fibers are both types.
A few immature, type 2C, fibers are present.

(Intermediate staining; Arrow)

ATPase pH 9.4 stain, Patient 1
Large fibers are type I & II.
Small fibers are type I & II.

ATPase, pH 9.4 stain

FSH: Other features

H&E stain
FSH fibers
Basophilic muscle fibers with clustered large nuclei

MHC-1 stain

MHC-1 is upregulated
  On the rim of all muscle fibers
  In the cytoplasm of smaller, immature fibers.

Sudan black stain

Fat replaces perimysial connective tissue

FSH: Later stage

H&E stain
More marked variation in fiber size

NADH stain
Hypertrophied fibers have pale centers.
Some small fibers are darkly stained

ATPase pH 9.4 stain, Patient 2
Large fibers are type I & II.
Small fibers are often type II.

Congenital FSH

H&E stain
  Muscle fiber size: Varied
  Many small basophilic fibers
  Mononuclear inflammatory cells: Around smaller, intermediate sized perimysial vessel
Congenital FSH
H&E stain
Varied muscle fiber size.
Basophilic (immature) fibers.
No hypertrophy.
Endomysial inflammation.
Congenital FSH: ATPase
ATPase pH 9.4 stain
Smaller fibers are
  Type I & II

MHC-1 stain
MHC-1: Abnormal upregulation on muscle fiber surfaces

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