Neuromuscular

Mitochondrial disease pathology: Single, Large mtDNA Deletions (KSS & PEO)


mtDNA deletion: Very large
  Size & Location: 5 kB; ~8,300 to 14,300; ATPase6 to ND5
  Clinical: Kearns-Sayre Syndrome


Muscle Fiber Morphology
  Scattered muscle fibers with
    Varied size
    Irregular internal architecture
    Large nuclei
    Basophilic cytoplasm
  Endomysial connective tissue: Normal


H&E stain

H&E stain

Ragged red muscle fibers
Mitochondrial proliferation: Varied Degrees
Muscle fiber cytoplasm
  Entirely replaced by mitochondria (Red) in some segments
  Coarse internal architecture in other segments

Gomori trichrome

Gomori trichrome


SDH stain
Mitochondrial proliferation: SDH+ muscle fibers with variably increased degrees of staining

SDH stain


COX stain
Cytochrome oxidase: Scattered muscle fibers with reduced or increased staining

COX stain

COX stain


Sudan black
Lipid: Increased size of lipid droplets in scattered muscle fibers

Sudan black

mtDNA deletion: Moderately large
  Size & Location: ND4 to ND5
  Clinical: PEO


H&E
Muscle fiber size: Mild variation
Basophilic mucle fibers: Occasional; Intermediate sized

H&E


Gomori trichrome
Ragged red muscle fibers
Mitochondrial proliferation: Mild
Muscle fiber cytoplasm
  Coarse internal architecture in some segments

Gomori trichrome


SDH stain
Mitochondrial proliferation
  SDH+ muscle fibers with variably increased degrees of staining


SDH stain

SDH stain


COX
Cytochrome oxidase: Scattered muscle fibers with reduced staining

COX


Sudan
Scattered muscle fibers with increased staining


ATPase pH 9.4
Fiber types: Type 2 predominance; Smallest fibers are type 1; No 2 C fibers

ATPase pH 4.3

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9/3/2013