Neuromuscular

FKRP Mutations

Muscular dystrophy
  Congenital (MDDGB5)
  Limb Girdle 2I (MDDGC5)

FKRP: Congenital Muscular Dystrophy (MDDGB5)


H & E stain
 
 
Myopathy: Mild active & chronic changes
  Necrosis & Regeneration: Scattered
  Fiber size: Varied
    Small fibers: Rounded
  Endomysial connective tissue: Normal or Slightly increased
  Internal nuclei: Some fibers

H & E stain
Gomori trichrome stain

Acid phosphatase stain
Necrotic muscle fibers: Phagocytosis

Esterase stain
Necrotic (pale) muscle fiber (Dark arrow)
  Type I fiber predominance

NADH stain
 Regenerating, immature muscle fibers
  Coarse internal architecture (White Arrow)
NADH stain
Fiber types

ATPase pH 9.4
Type I fiber predominance
ATPase pH 4.3
Scattered 2C fibers
Neuromuscular Junctions: Normal

Esterase stain
Intramuscular nerves: Normal

VvG stain

α Dystroglycan
FKRP mutations:
  Absent α-Dystroglycan around muscle fibers
α Dystroglycan
Control muscle:
  Normal α-Dystroglycan around muscle fibers
Desmin stain
Desmin: Stains cytoplasm in small regenerating fibers

MHC Class I stain
MHC-I is abnormally present on clusters of muscle fibers
MHC Class I stain

FKRP: Limb-Girdle Muscular Dystrophy 2I (LGMD 2I; MDDGC5)


H&E stain
FKRP: Chronic & Ongoing Myopathy
  Fiber size: Varied; Hypertrophic & Small
  Nuclei: Some are Internal or Large
  Partially fused (or Split) fibers
  Necrosis & Regeneration: Scattered

H&E stain

H&E stain
FKRP: Ongoing Myopathy
  Necrosis & Regeneration: Scattered
  Immature muscle fibers
    Internal architecture: Coarse
    Nuclei: Large
    Size Intermediate or Small

H&E stain

Gomori trichrome stain
FKRP: Ongoing Myopathy
  Necrosis: Muscle fibers replaced by phagocytic cells
  Immature muscle fibers: Coarse internal architecture
    Internal architecture: Coarse
    Nuclei: Large
    Size Intermediate or Small

NADH stain

Alkaline phosphatase stain
FKRP: Ongoing Myopathy
  Immature muscle fibers: Cytoplasm stains for Alkaline phosphatase
  Necrotic fibers: Replaced by Acid phosphatase positive histiocytic cells

Acid phosphatase stain
FKRP: Ongoing Myopathy
  Immature muscle fibers: Intermediate color with ATPase pH 4.3 stain

ATPase pH 4.3 stain

H&E stain
FKRP: Chronic Myopathy
  Endomysial connective tissue: Increased between muscle fibers
  Partially fused (or Split) fibers
  Nuclei: Some are Internal
  Muscle fiber hypertrophy

VvG stain

Gomori trichrome stain
Partially fused (or Split) fiber

VvG stain

Congo Red stain
FKRP: Chronic Myopathy
  Amyloid: Deposited in vessel walls & around small msucle fibers

Congo Red stain

Congo Red stain
FKRP: Other changes

ATPase pH 9.4 stain
Type 2 fiber (Dark) predominance
FKRP: "Immune" changes

MHC Class I stain
MHC Class I: Upregulation by muscle fibers, Diffuse or Patchy

Acid phosphatase stain
FKRP: "Immune" changes
  Histiocytic cells (Acid phosphatase & CD4 positive) are present in Perimysial and Endomysial connective tissue

CD4 cell stain
FKRP Myopathy
  Reduced staining for carbohydrate moiety on surface of muscle fibers
  Similar patterns seen with
    Other hereditary disorders of α-Dystroglycan glycosylation
    Graft vs Host myopathies

α-Dystroglycan - Green; Caveolin-3 - Red
α-Dystroglycan (Green): Varied patterns
  Reduced or Absent on the surface of some muscle fibers (Above)
  Severely reduced on the surface of most fibers (Below)

α-Dystroglycan - Green; Caveolin-3 - Red

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10/17/2023