Rapsyn

Congenital MG: Rapsyn mutations

7 year old male with Asn88Lys & K373 deletion mutations

H&E stain

Muscle fibers
Varied sizes

H&E stain

Muscle fibers: Varied sizes
Small fibers
Shapes: Angular, Polygonal or Rounded
Size: Intermediate

H&E stain

Gomori trichrome stain

Muscle fibers
Varied sizes
Intramuscular nerves: Normal

VvG stain

NADH stain

Internal architecture: Coarse in most muscle fibers

NADH stain

ATPase pH 9.4 stain

Fiber types
Type I predominant
Type II fibers: Tend to be smaller
Type 2C fibers: Few scattered

ATPase pH 4.3 stain

Esterase stain

Neuromuscular Junctions
Pale
Thin
May be multisegmented

Esterase stain

Esterase stain

52 year-old female with episodic & fixed weakness + Rapsyn mutations, Homozygous Asn88Lys

From: R Bucelli; M Al-Lozi

Rapsyn CMG: Repetitive Nerve Stimulation

H&E stain

Muscle morphology
Scattered small, polygonal muscle fibers

ATPase pH 4.3 stain

Muscle fiber types
Moderate type 2 fiber predominance

Neuromuscular Junctions
Some are small, elongated or multi-segmented

Esterase stain

LC3 stain

LC3 staining of Muscle fiber cytoplasm: Unexplained

LC3 stain