Inflammatory Myopathy

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Inflammatory Myopathy

Last updated on Tuesday, September 9 2008 by jdmiles

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Churg-Strauss arteritis involving epimysial artery, H&E stain x 200
Churg-Strauss arteritis is one of the necrotizing vasculitides affecting medium-sized epimysial arteries. Although the prominent eosinophilic infiltrate is suggestive of Churg-Strauss arteritis, there is considerable histologic overlap among these vasculitides, requiring clinical correlation.

Churg strauss arteritis involving skeletal muscle, H&E stain x 100
Necrotizing vasculitis involving medium sized epimysial arteries occurs in patients with systemic, rather than muscle restricted, vasculitis. Note also small group atrophy within the accompanying skeletal muscle, suggestive of concomitant vasculitic neuropathy

Churg Strauss arteritis on muscle biopsy, H&E stained section x 40
As the name implies, Churg-Strauss arteritis involves the vasculature, not the skeletal muscle itself.

Dermatomyositis, H&E stained section of paraffin embedded skeletal muscle x 400
Extension of the perimysial lymphocytic infiltrate into the adjacent skeletal muscle does not obviate the diagnosis.

Dermatomyositis, H&E stained section of paraffin embedded muscle x 200
Although the inflammatory infiltrate extends from the perimysium to surround some of the muscle fibers, attention to the chronic perimysial scarring supports a diagnosis of dermatomyositis rather than polymyositis.

Dermatomyositis, H&E stained section of frozen skeletal muscle x 100
Perimysial vascular damage results in skeletal muscle ischemia manifest as subperimysial atrophy.

Dermatomyositis, H&E stained sections of paraffin embedded skeletal muscle
A mixed inflammatory infiltrate, including eosinophils and plasma cells, characterizes dermatomyositis

Paraneoplastic myositis, H&E stained section
Inflammatory muscle disease may represent a paraneoplastic syndrome, particularly in older individuals.

Perivascular infiltrate, H&E stained section of paraffin embedded skeletal muscle x200
Perivascular infiltrate with perimysial scarring in a patient with chronic collagen vascular disease associated myositis.

Perivascular infiltrate, H&E stained paraffin embedded section x400
Perivascular infiltrates and collagen vascular disease associated myositis are composed of a mixture of lymphocytes, plasma cells, and eosinophils which follow complement activation on the endothelial cells within the muscle.

Polymyositis, H&E stained section
Polymyositis is characterized by endomysial lymphocytic infiltrates accompanied by myofiber degeneration.

Churg-Strauss arteritis, H&E stained section x 400
Although Churg-Strauss arteritis is characterized by an abundant eosinophilic inflammatory infiltrate, similar findings may be seen in patients with Wegener's granulomatosis and polyarteritis nodosa.

Polymyositis, CD20 immunohistochemical staining x600
The overwhelming majority of the inflammatory cells within the endomysium of patients with polymyositis consist of or reactive T cells. Therefore, CD20 staining for B cells highlights only rare immunopositive cells.

Polymyositis, CD3 immunohistochemical staining x600
Polymyositis is characterized by autoreactive endomysial CD3 positive T cells.

Polymyositis, immunohistochemical staining for CD68 x600
CD68 positive cells (macrophages) are expected whereever there is necrosis of muscle fibers.

Polymyositis, paraffin-embedded H. E. stained section x 200
Polymyositis is characterized by autoreactive T cells, which invade into morphologically normal endomysial muscle fibers.

Polymyositis,paraffin-embedded, H&E stained section 400x
Polymyositis is characterized by a monomorphous accumulation of auto reactive T cells, without admixed eosinophils and plasma cells.

Polymyositis, paraffin-embedded H&E stained section x 600
Polymyositis is characterized by a nearly pure population of T lymphocytes, without evidence of complement activation