SPINAL MUSCULAR ATROPHY (5q)

SMA 5q: General Features

H&E stain	ATPase pH 9.4 stain
Grouped atrophy   Small muscle fibers are often rounded   Pyknotic nuclear clumps are not present. Large muscle fibers are hypertrophied.	Large fibers: Hypertrophied & Type I Small fibers: Type I or II

SMA, Type 2

H&E stain	H&E stain
Large grouped atrophy
H&E stain

ATPase, pH 9.4	ATPase, pH 9.4	ATPase, pH 4.3
Small muscle fibers may be varied types (Left) or mostly type II (Middle) Clusters of large type I muscle fibers		Many small fibers are type 2C

Esterase	Esterase
Neuromuscular junctionsw on large (Left) and small (Right) muscle fibers.

VvG	Toluidine blue
Intramuscular nerve: Unremarkable	Sensory nerve   Normal numbers of axons   Thinly myelinated axons consistent with young age.

NADH	NADH
Small muscle fibers stain darkly on NADH

SMA, Type 1

H & E	H & E
Many muscle fibers are small. A few hypertrophied fibers are present

SMA, Congenital (Type 0)

H & E	H & E
Only small muscle fibers are present. Small fibers have moderate variation in size

SMA, Type 3

H & E

Grouped atrophy. Larger muscle fibers are not promiently hypertrophied.

ATPase pH 9.4	NADH
Variable involvement of fascicles.   Top: Scattered small fibers. Large fibers are type 1.   Bottom: Few small fibers. Type 2 predominance.         Abnormal intermediate-staining fibers.	Variable involvement of fascicles.   Top: Scattered small fibers. Most fibers are dark-stained.   Bottom: Few small fibers. Most fibers are pale-stained.

VvG

Grouped atrophy. Larger muscle fibers are not promiently hypertrophied. Intramuscular nerves have mildly reduced axon numbers.

Esterase

Neuromuscular junctions. Present on large and small muscle fibers. Mildly large, but not multi-segmented.