Jo-1 Myositis

IMMUNE MYOPATHIES WITH PERIMYSIAL PATHOLOGY (IMPP)

Clinical syndromes
Dermatomyositis: Adult (variant) type
Graft-vs-Host
Myopathies with
Anti-Jo-1 Antibodies
Other tRNA synthetase antibodies
High Aldolase & Normal CK
Minocycline
Dermatomyositis vs IMPP
IMPP muscle pathology

IMPP: General

Clinical Features
Immune myopathies: Similar to Jo-1 & tRNA synthetase antibody related immune myupathies

Pathology
Perimysial damage: Prominent
Probably same as: Dermatomyositis: Adult variant

Comparison: IMPP vs. Dermatomyositis + Vascular pathology (DM-VP) Pathology: Both IMPP and DM-VP have Muscle fiber pathology that is most prominent at the edge of fascicles Immune myopathy Skin rash: DM-VP & Some IMPP DISTINCTIVE DIFFERENCES between the syndromes
		IMPP	Dermatomyositis + Vascular pathology
CLINICAL	Age range	Adult	Child or Adult
	Skin	Raynaud's Mechanic's hands	Heliotrope rash
	Interstitial lung disease	Common	Uncommon
	Myalgias	Common	Occasional
ANTIBODY	Myositis-associated	Jo-1 tRNA synthetase	Mi-2 p140; p155
MUSCLE PATHOLOGY	Focal inflammation Location Type	Perimysium Macrophage-like	Perivascular, Mononuclear cells Often with CD20 cells
	Perimysium pathology Fragmentation Cellularity Without myopathy Alkaline phophatase staining	Common Macrophage-like Some patients Some patients	Occasional Mononuclear Never Unusual
	Perifascicular muscle fibers COX staining reduced Necrosis & Regeneration Internal architecture Caveolin-3 aggregates	Never Common Regeneration Rare	Most patients Unusual Vacuoles & Aggregates Common
	Capillaries Near perifascicular path Ulex staining C_5b-9 deposition Alkaline phophatase staining Amid perifascicular path Ulex staining C_5b-9 deposition Alkaline phophatase staining	Normal Absent Absent Normal Absent Absent	Large Few Common Absent Common Absent

IMPP Muscle Pathology

H&E stain

Perimysial fragmentation

The perimysium is loculated with many focal clear areas
Cells in the perimysium are most frequently macrophages. Features include
- Large nuclei
- Prominent cytoplasm
- Staining for Acid Phosphatase, Esterase and CD-68
Adjacent muscle fibers may be normal (Bottom left) or show
- Perifascicular myopathy: Regeneration & Necrosis (Bottom right)
- Small size


H&E stain Perimysial inflammation	Acid phosphatase Perimysial cells: Acid phosphatase positive	Acid phosphatase Perimysial cells: Acid phosphatase positive


Esterase Perimysial inflammation Esterase positive macrophages	Acid phosphatase stain CD-68 positive cells in perimysium and endomysium

Alkaline phosphatase stain Alkaline phosphatase staining of perimysium

H&E stain

Perifascicular myopathy & atrophy
Regeneration & Necrosis of perifascicular fibers

Immunocytochemistry

N-CAM positive atrophic muscle fibers

Immunocytochemistry

MHC Class 1 positive muscle fibers
Positive fibers are perifascicular and have normal size
A similar pattern may occur in mild dermatomyositis

Return to Inflammatory myopathies
Return to Jo-1 myositis

12/14/2011