Myotubular

Centronuclear (Myotubular) Myopathy

General features
Ultrastructure
Adult
MTM1, Missense
Titin
Juvenile
DNM2 mutations
Myopathic
Muscle fibers
Ultrastructure
Necklace fibers
Abnormal fiber types
Punctate, Small fibers
Childhood
Infant
MTM1, Stop

General: Pathologic differential diagnosis

Central nuclei
- Clustered central nuclei: Bin1
- Central & Internal, Multiple: TTN
Central muscle fiber staining
- DHPR: MTM1; Bin1
- RYR1: MTM1; DNM2; Bin1
- Desmin: MTM1; DNM2; Bin1
- Caveolin-3: Bin1
- Histochemistry, punctate: DNM2
Radiating sarcoplasmic strands (NADH): DNM2
Necklace fibers
- MTM1: Severe & Mild
- DNM2 (2% of patients)
Connective tissue pathology: DNM2
- Endomysial connective tissue: Increased
- Perimysium: Replaced by fat
Type I fiber predominance/smallness: MTM1; DNM2, Bin1, TTN
Core-like regions: RYR1; TTN

Centronuclear myopathy: Infantile

A single central nucleus is present in many muscle fibers

From: T Mozaffar

H&E stain

H&E stain

H&E stain

A single central nucleus is present in many muscle fibers

H&E stain

Toluidine blue stain

Central nuclei & abnormal internal architecture

Toluidine blue stain

Toluidine blue stain

Toluidine blue stain

A single central nucleus is present in many muscle fibers

Electron microscopy from T Mozaffar

Type I (light) muscle fibers tend to be smaller than type II.
Clear regions occur in center of some fibers.

ATPase stain, pH 9.4

ATPase stain, pH 9.4

Internal architecture: Small "Halo" muscle fibers.
Darker staining: Central regions
Clear rim around edge
Common in MTM1 mutations

NADH stain

NADH stain

Centronuclear myopathy: Childhood

H&E stain	H&E stain	NADH stain	ATPase stain, pH 9.4
Some smaller muscle fibers Central nuclei Other muscle fibers Central regions are basophilic.		Abnormal internal architecture. Central dark staining. Coarse Radial strands	Type I (light) muscle fibers Smaller than type II Clear central regions

Muscle fibers with abnormal internal architecture, including "radial" strands and necklace fibers

NADH stain

Centronuclear myopathy: Juvenile with Necklace fibers

H&E stain	H&E stain
Muscle fiber sizes: Bimodal distribution Central nuclei: Especially in smaller fibers Clefts: In center of other muscle fibers H&E stain

Gomori trichrome stain

Central nuclei: Especially in smaller fibers
Clefts: In center of other muscle fibers
Rings (Necklaces): In some muscle fibers

Gomori trichrome stain

Necklace fibers
Dark fibers: Rings
Light fibers: Irregular internal architecture

NADH stain

NADH stain

ATPase pH 9.4 stain

Small muscle fibers
Most are type 1
Contain central clear regions

ATPase pH 4.3 stain

Esterase stain

Centronuclear myopathy: Juvenile with many Central nuclei & Type 2C fibers

H&E stain

Many muscle fibers have single central nuclei

H&E stain

VvG stain

NADH stain
Abnormal internal architecture around central nuclei

ATPase pH 9.4 stain

ATPase pH 4.3 stain
Many abnormal, intermediate-staining (type 2C), muscle fibers

Centronuclear myopathy: Juvenile with Small muscle fibers & Punctate central NADH stain

H&E stain

Many muscle fibers have single central nuclei

H&E stain stain

NADH stain
Punctate central staining in many muscle fibers

ATPase pH 9.4 stain

Type 1 muscle fibers are smaller than type 2

ATPase pH 4.3 stain

Centronuclear myopathy: Teenage, DNM2 mutation

H&E stain
Myopathic muscle Central nuclei: Single; In most muscle fibers Endomysial connective tissue: Increased between muscle fibers Fat: Replaces perimysium and some muscle Gomori trichrome stain	H&E stain
NADH stain Abnormal internal architecture Muscle fibers may have radial strands, necklace formations or central "dots"	NADH stain
NADH stain

ATPase pH 9.4 stain

Fiber type pathology
Type 1 fibers: Small, Predominant

ATPase pH 4.3 stain Fiber types: All type I	Acid phosphatase stain
Cytochrome oxidase stain	Central abnormalities in internal architecture Lysosomal (Acid phosphatase positive; Above) Mitochondrial (COX positive; Left) Endoplasmic reticulum (Caveolin-3 positive; Below) Caveolin-3 stain
Cytoplasmic abnormalities: Dystrophin & Desmin staining Dystrophin stain	Desmin stain
Nuclei: Large central nuclei with irregular emerin Emerin stain

Centronuclear Myopathy, DNM2 mutations: Individual muscle fibers

H&E stain stain

Central Nuclei: Often large

H&E stain

Gomori trichrome stain

Central Nuclei: Often large with pale centers

Congo red stain

H&E stain

Other Central Pathology
Multiple central nuclei
Central pallor

VvG stain

Internal Architecture
Abnormal internal regions

VvG stain

NADH stain

Internal Architecture
Radial strands
Central clustering

NADH stain

NADH stain

Internal Architecture
Radial strands

NADH stain

Ultrastructure From C Cai

Ultrastructure From C Cai

Ultrastructure From C Cai

Ultrastructure From C Cai

Centronuclear myopathy: Infant male (1 year), MTM1 stop mutation (Arg24X) ¹

H&E stain

Central nuclei: Single; Large; In many muscle fibers
Muscle fiber size: Moderately varied
Perimysium: Replaced by fat in some regions

Congo red stain

H&E stain

Central nuclei: Single; Large; In many muscle fibers
Muscle fiber size: Moderately varied
Endomysial connective tissue: Normal to slightly increased

Congo red stain

Abnormal Muscle Fibers
Many fibers have central nuclei
A few smaller muscle fibers have basophilic cytoplasm & clustered, irrregular-shaped nuclei

H&E stain

Acid phosphatase stain

Acid phosphatase staining: Around central nuclei; Central regions in other muscle fibers

VvG stain

Peripheral halos: Pale; Subsarcolemmal

Gomori trichrome stain

PAS stain

SDH stain

Peripheral halos: Mitochondria concentrated in center of muscle fibers

COX stain

Peripheral halos: SR concentrated in center of muscle fibers

NADH stain

VvG stain

ATPase pH 9.4 stain

Fiber types
Type 1 predominance
Central clear regions
No halos
Some small muscle fibers are type 2C (Below)

ATPase pH 4.3 stain

Neuromuscular junctions: Dark stained; Large

Esterase stain

Perimysial Vein & Artery
Normal structure

VvG stain

Centronuclear myopathy (CNMX): Adult male (43 years), MTM1 missense mutation (V447M)

H&E stain

MTM1 Centronuclear Myopathy: Adult
Internal nuclei: 3 populations of muscle fibers
Single: Often central
Multiple: Often somewhat linear arrangement
None
Fiber size vatiation
Moderate
Scattered intermediate-sized round or polygonal fibers

VvG stain

H&E stain

MTM1 Centronuclear Myopathy: Adult
Internal nuclei: 3 populations of muscle fibers
Single: Often central
Multiple: Often somewhat linear arrangement
None
Endomysial connective tissue: Normal

Gomori trichrome stain

VvG stain

MTM1 Centronuclear Myopathy: Adult
Internal nuclei: 3 populations of muscle fibers
Single: Often central
Multiple: Often somewhat linear arrangement
None: Some fibers with abnormal central regions but no nuclei (Below)
Muscle fiber internal architecture
Some fibers have
Central dark staining
Sarcoplasmic reticulum with radial strands or irregular shapes
Irregular cytoplasm staining around central nuclei
Fiber size vatiation
Moderate
Scattered intermediate-sized round or polygonal fibers
Endomysial connective tissue: Normal

VvG stain

ATPase pH 9.4 stain

MTM1 Centronuclear Myopathy: Adult
Internal nuclei: 3 populations of muscle fibers
Single: Often central; Mostly in Type 1 fibers
Multiple: Often somewhat linear arrangement; Mostly in Type 2 fibers
None: Some fibers with abnormal central regions but no nuclei, Mostly in Type 1 fibers (Below)
Muscle fiber internal architecture
Type 2 fibers have more irregular internalarchitecture (Above)
Fiber types
Type 1 fibers
Predominance: In some areas (Below)
Smallness: In some areas; Intermediate sized; More smallness in fibers with central nuclei
Type 2 fibers
More likely to have: Multiple or No internal nuclei

ATPase pH 4.3 stain

NADH stain

MTM1 Centronuclear Myopathy: Adult
Type 1 fibers (Dark)
Predominance: In some areas
Smallness
More likely to have
Aggregates, some clustered around internal nuclei
Radial strands

NADH stain

H&E stain

MTM1 Centronuclear Myopathy: Adult
Internal nuclei
Many fibers have single central nuclei
Gomori trichrome stain (Below)
Myonuclei often have clear centers
One fiber has a central red-stained region (Arrow)

Gomori trichrome stain

VvG stain

MTM1 Centronuclear Myopathy: Adult
Internal nuclei
Many fibers have single central nuclei

VvG stain

Congo red stain

MTM1 Centronuclear Myopathy: Adult
Internal nuclei
Many fibers have single central nuclei
Some fibers have abnormal (blurred) internal architecture around internal nuclei (Below)

Congo red stain

VvG stain

H&E stain

MTM1 Centronuclear Myopathy: Adult
Internal nuclei
A minority of fibers have several internal nuclei

H&E stain

Gomori trichrome stain

MTM1 Centronuclear Myopathy: Adult
Internal nuclei
A minority of fibers have several internal nuclei
These fibers tend to have more irregular internal architecture

Gomori trichrome stain

VvG stain

MTM1 Centronuclear Myopathy: Adult
Internal nuclei
A minority of fibers have several internal nuclei
These fibers tend to have more irregular internal architecture

VvG stain

Congo red stain

VvG stain

MTM1 Centronuclear Myopathy: Adult
Muscle fibers: Internal architecture
Some fibers have irregular internal architcture extending from their center

VvG stain

VvG stain

MTM1 Centronuclear Myopathy: Adult
Muscle fibers: Internal architecture
Some fibers have central structural abnormality without central nuclei

Congo red stain

NADH stain

MTM1 Centronuclear Myopathy: Adult
Muscle fibers: Internal architecture changes include
Irregular sarcoplasmic aggregates
Sarcoplasmic staing around internal nuclei

NADH stain

MTM1 Centronuclear Myopathy: Adult
Muscle fibers: Internal architecture changes include
Dark central structures with radial strands
Irregular sarcoplasmic aggregates
Sarcoplasmic staing around internal nuclei