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. Author manuscript; available in PMC: 2016 Oct 1.
Published in final edited form as: Arthritis Care Res (Hoboken). 2015 Oct;67(10):1416–1425. doi: 10.1002/acr.22620

Table 1. Diagnostic Category Definitions (adapted from ENMC criteria (28)).

  1. Endomysial inflammatory cell infiltrate (T-Cells) surrounding and invading non-necrotic muscle fibers.

  2. Endomysial CD8+ T-cells surrounding, but not definitely invading non-necrotic muscle fibers.

  3. Perifascicular atrophy.

  4. Perivascular, perimysial inflammatory cell infiltrate.

  5. Scattered endomysial CD8+ T-cells infiltrate that does not clearly surround or invade muscle fibers.

  6. Many necrotic muscle fibers as the predominant abnormal histological feature. Inflammatory cells are sparce or only slight perivascular; perimysial infiltrate is not evident.

Polymyositis: Muscle biopsy criteria include a or b, and exclude c.

Dermatomyositis: Muscle biopsy criteria include c.

Non-specific myositis: Muscle biopsy criteria include d or e, and exclude all others.

Necrotizing myopathy: Muscle biopsy criteria include f, and exclude all others.

Acute denervation: Muscle biopsy reveals esterase-positive angular atrophic fibers and excludes all others.

Fibrosis only: Muscle biopsy reveals increased connective tissue and excludes all others.