Neuromuscular

Inflammatory Myopathies with Vacuoles, Aggregates & Mitochondrial Pathology (IM-VAMP)

Myositis with mitochondrial pathology (PM-Mito) subtype

Inflammation
  Endomysial
  Focal invasion of muscle fibers
Myopathic changes
Mitochondrial disorders
Other

Variant syndrome
  IBM

PM-Mito: Muscle pathology

PM-Mito: Myopathy, Inflammatory


VvG stain
Muscle fibers
  Sizes: Varied; Largest fibers hypertrophied
  Internal nuclei
  Immature
    Small, Darker stained cytoplasm, Large nuclei
    Distribution: Scattered
Connective tissue, endomysial
  Increased, mild to moderate
Inflammation
  Endomysial lymphocytes
  Some focal invasion of muscle fibers

H&E stain


Gomori trichrome stain
PM-Mito: Myopathy, Inflammatory

H&E stain

Gomori trichrome stain


PM-Mito: INFLAMMATION


H&E stain
Cell foci: Predominantly Endomysial
Focal invasion of muscle fibers by immune cells

H&E stain

Cell foci contain: Lymphocytes & Histiocytes (Acid phosphatase positive)

Acid phosphatase stain

IM-VAMP: MITOCHONDRIAL CHANGES

Cytochrome oxidase (COX) negative muscle fibers


Cytochrome oxidase stain

Succinate Dehydrogenase (SDH) positive muscle fibers


SDH stain

PM-Mito: Other features

Perivascular Inflammation: Occasional

MHC-I Upregulation on sarcolemma: Diffuse


LC-3 aggregates in muscle fibers


PM-Mito: Capillary pathology

Capillary sizes: Some are large
Endothelial cells: May stain for acid phosphatase (Dark arrow)
Neighboring histiocytic cells (White arrow)

Acid phosphatase stain

Return to Inflammatory myopathies
Return to Polymyositis with mitochondrial disorders

7/18/2021