IBM3: Adult; MYH2

H&E stain
Fiber sizes: Marked variation; Hypertrophy & Atrophy
Internal nuclei: Many fibers
Small fibers: Rounded; Some large pyknotic nuclear clumps
Large fibers: Partial fusion

H&E stain

H&E stain
Muscle fiber pathology
Internal nuclei
Partial fusion
Pyknotic nuclear clumps

Congo red stain

Congo red stain
Vacuoles: Contain basophilic granular debris

Congo red stain

Congo red stain
Nuclei: Large; Internal

ATPase pH 9.4 stain
Type 2 fiber predominance: Many fibers are 2C

ATPase pH 4.3 stain

NADH stain
Internal architecture
  Some small fibers are dark stained
  Large fibers have irregular staining

Fiber Type Abnormalities

Type 1 fibers: Commonly express both MYH7 & MYH4
Type 2 fibers (H): Commonly express multiple MYH types (MYH7, MYH2, MYH1& MYH4)
Branched fibers (B) are present

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