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
Dermatomyositis vs IMPP

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

Differences between IMPP and Dermatomyositis
Both IMPP and Dermatomyositis have
Muscle fiber pathology that is most prominent at the edge of fascicles
Immune myopathy
Some patients with IMPP have a Skin rash.
However, there are distinctive differences between the syndromes

		IMPP	Dermatomyositis
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-specific	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	Never Common Regeneration	Most patients Unusual Vacuoles & Aggregates
	Capillaries near perifascicular pathology Ulex staining C_5b9 deposition Alkaline phophatase staining	Normal Absent Absent	Absent Common Common

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

Return to Inflammatory myopathies
Return to Jo-1 myositis

11/18/2009