Neuromuscular

Ryr1 Recessive Myopathy
Muscle Pathology: General
Patient
3 week old male with: Ophthalmoplegia & Diffuse weakness + hypotonia
Ryr1 mutations: Bi-allelic; Missense; Leu3554Pro, Gly4782Arg
See: Same patient at 2 years of age

H & E stain
Muscle Fiber sizes
  Bimodal distribution
Nuclei
  A few small fibers have central nuclei
  Morphology: Some haver irregular shapes

H & E stain

Congo red stain
Fiber sizes
  Bimodal distribution

Gomori trichrome stain

VvG stain
Fiber sizes
  Bimodal distribution
Muscle spindle
  > 10 muscle fibers

VvG stain

NADH stain
Small Muscle Fibers
  Stain dark on NADH & COX

COX stain

ATPase pH 4.3 stain
Small Muscle Fibers
  Type 1: Stain dark on ATPase pH 4.3 & Intermediate on ATPase pH 9.4
Type 2C immature fibers
  Many
  Intermediate stained on ATPase pH 4.3

ATPase pH 9.4 stain
Small Muscle Fibers
  Acid phosphatase moderately stains cytoplasm

Acid phosphatase
Neuromuscular junctions
  Dark esterase staining

Esterase stain
Ryr1 mutations
Same patient as above at 2 years of age

H & E stain
Muscle Fiber sizes
  Bimodal distribution

H & E stain

Congo red stain
Muscle Fiber sizes
  Bimodal distribution
Nuclear morphology
  Irregular shapes

Congo red stain

Gomori trichrome stain
Muscle Fiber sizes
  Bimodal distribution

VvG stain

NADH stain
Small Muscle Fibers
  Moderately dark staining
  Some have membrane aggregates

NADH stain
Small Muscle Fibers
  Some have clear regions

COX stain

ATPase pH 4.3 stain
Type I fibers are generally smaller than type 2 fibers
Immature type 2C fibers
  Few
  Scattered
Capillaries
  Have moderate ATPase staining

ATPase pH 4.3 stain

ATPase pH 4.3 stain

ATPase pH 9.4 stain

Acid phosphatase stain
Small Muscle Fibers
  Acid phosphatase moderately stains cytoplasm

Acid phosphatase stain
Return to Ryr1

6/22/2026