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Gastrocnemius-Myalgia Symdrome

Muscle fibers   Perimysial   Capillaries Vessels Perimysial connective tissue

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Muscle Fiber Pathology

H&E stain

Muscle Fibers
  Minimal damage
  Sizes
    Moderate Atrophy
    Mild variation
Perimysial Vessel
  Associated inflammation
  Pale walls

H&E stain

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MHC Class I stain

MHC Class I
  Mildly increased on muscle fiber surfaces

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muscle Fibers

From: R Schmidt

Sarcomere structure
  Normal
Mitochondria
  Often large

From: R Schmidt

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Vessels

Perimysial Vessel Pathology: Associated Inflammation

H&E stain

Perivascular Inflammation

VvG stain

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Acid phosphatase stain

Acid phosphatase stains: Histiocytes in wall of vein & in perimysial connective tissue

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MHC Class I stains cells in & around vessel walls

MHC Class I stain

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H&E stain

Vein Pathology
  Walls: Pale

VvG stain

Vein Pathology
  Walls: Pale; Absent fibrils
Arteries: Normal

VvG stain

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Alkaline Phosphatase stain

Alkaline phosphatase stains connective tissue in perimysial vessel

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C5b-9 stain

C_5b-9 stains cells in wall of vein & abnormal fibrils in artery wall

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Capillaries

ATPase pH 4.3 stain

ATPase stains endomysial capillaries

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CD163 stain

CD163 stains cells near endomysial capillaries

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MxA stain

MxA stains cells near endomysial capillaries

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Ulex stain

Ulex stains normal numbers of endomysial capillaries

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Capillaries
  Extracellular endomysial vesicles near capillaries

From: R Schmidt

From: R Schmidt

Extracellular endomysial vesicles near capillaries

From: R Schmidt

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Capillaries

From: R Schmidt

Abnormal pericytes in capillary wall
Cell, probably lymphocyte, below capillary

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Damaged endomysial capillary

From: R Schmidt

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Damaged Capillary
  No lumen
  Endothelial cell with cytoplasmic vesicles inside a basal lamina
  Erythrocytes & Vesicles in Endomysium

From: R Schmidt

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Endomysial Cells & Vesicles

From: R Schmidt

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Small cell with many mitochondria below irregular capillary
Extracellular vesicular debris

From: R Schmidt

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Perimysial Connective Tissue

Perimysial Pathology

Alkaline Phosphatase stain

Alkaline phosphatase stains perimysial connective tissue

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Return to Gastrocnemius-Myalgia

1/9/2026