Neuromuscular

MELAS PATHOLOGY (A3243G mutation)

Brain
Muscle


MELAS: Muscle fiber pathology

Scattered fibers with clear rim

H&E stain
"Ragged red" fibers

Gomori trichrome stain


Gomori trichrome stain


Gomori trichrome stain

Muscle fibers with increased SDH stain
  Scattered through muscle
  Variable degrees

Fibers with increased SDH stain
  Scattered through muscle
  Variable degrees

Muscle fiber with increased SDH stain:
  Individual mitochondria within muscle fiber are enlarged
    compared to surrounding fibers


Cytochrome Oxidase (COX) stain: Reduced or Increased
Muscle fibers may have reduced, normal or increased COX staining (Right)
Lipid accumulation
  Increased Sudan black stain in muscle fiber
  with mitochondrial proliferation


Muscle fibers with Mitochondrial proliferation (Increased SDH stain)
Muscle fibers with increased SDH stain may also have increased COX stain

Succinic dehydrogenase (SDH) stain

Cytochrome oxidase (COX) stain

MELAS: SDH staining of intramuscular vessels: Increased

 
Succinic dehydrogenase (SDH) stain

MELAS: Increased SDH staining of medium sized perimysial vessels

Normal: Mild SDH staining of medium sized perimysial vessels
 
Succinic dehydrogenase (SDH) stain




Brain pathology in MELAS

MRIs during "stroke-like" episodes
  • Cortical lesions (Posterior): Spares white matter
  • Lesion location
    • Not confined to territory of single vessel
    • Involves only part of territory of several vessels
  • Swelling
  • Mutation: A3243G

FLAIR image

T2 weighted image

From: Cindy Ly

CT during episode of homonymous hemianopia

Medial occipital lesion (Arrow)

Enlarged ventricles
Late in disease course

MRI: Severe involvement
  of occipital cortex

Severly abnormal temporal gray matter.
Temporal horn of ventricles is enlarged.

Return to Mitochondrial pathology
Return to Mitochondrial syndromes
Return to Muscle biopsies

8/26/2015