2017 EULAR/ACR Idiopathic Inflammatory Myopathy (IIM) Classification Criteria

Applies the 2017 EULAR/ACR criteria — weighting clinical features, autoantibody, enzymes, and optional muscle-biopsy findings into a probability — to classify suspected idiopathic inflammatory myopathy for research/cohort use, only after other causes are excluded; not a stand-alone diagnostic test.

Muscle biopsy data available? (selects the scoring column, intercept, and cutoff)

Age at onset of first symptom assumed related to disease

Objective symmetric weakness, usually progressive, of the proximal upper extremities

Objective symmetric weakness, usually progressive, of the proximal lower extremities

Neck flexors relatively weaker than neck extensors

In the legs, proximal muscles relatively weaker than distal muscles

Heliotrope rash

Gottron's papules

Gottron's sign

Dysphagia or esophageal dysmotility

Anti-Jo-1 (anti-histidyl-tRNA synthetase) autoantibody present

Elevated serum CK OR LDH OR AST OR ALT (any one above the upper limit of normal)

BIOPSY: Endomysial infiltration of mononuclear cells surrounding, but not invading, myofibres (scored only with biopsy)

BIOPSY: Perimysial and/or perivascular infiltration of mononuclear cells (scored only with biopsy)

BIOPSY: Perifascicular atrophy (scored only with biopsy)

BIOPSY: Rimmed vacuoles (scored only with biopsy)