Journal of Rheumatic Diseases

Table. 2.

EULAR/ACR classification criteria for adult and juvenile IIMs

When no better explanation for the symptoms and signs exists, these classification criteria can be used

Variable Definition Score points

Without muscle biopsy With muscle biopsy
Age of onset
Age of onset of first symptom assumed to be related to the disease ≥18 years and <40 years ≥18 age (years) at onset of first symptom assumed to be related to the disease <40 1.3 1.5
Age of onset of first symptom assumed to be related to the disease ≥40 years Age (years) at onset of first symptom assumed to be related to the disease ≥40 2.1 2.2
Muscle weakness
Objective symmetric weakness, usually progressive, of the proximal upper extremities Weakness of proximal upper extremities as defined by manual muscle testing or other objective strength testing, which is present on both sides and is usually progressive over time 0.7 0.7
Objective symmetric weakness, usually progressive, of the proximal lower extremities Weakness of proximal lower extremities as defined bymanual muscle testing or other objective strength testing, which is present on both sides and is usually progressive over time 0.8 0.5
Neck flexors are relatively weaker than neck extensors Muscle grades for neck flexors are relatively lower than neck extensors as defined by manual muscle testing or other objective strength testing 1.9 1.6
In the legs, proximal muscles are relatively weaker than distal muscles Muscle grades for proximal muscles in the legs are relatively lower than distal muscles in the legs as defined by manual muscle testing or other objective strength testing 0.9 1.2
Skin manifestations
Heliotrope rash Purple, lilac-colored, or erythematous patches over the eyelids or in a periorbital distribution, often associated with periorbital edema 3.1 3.2
Gottron’s papules Erythematous to violaceous papules over the extensor surfaces of joints, which are sometimes scaly. May occur over the finger joints, elbows, knees, malleoli, and toes 2.1 2.7
Gottron’s sign Erythematous to violaceous macules over the extensor surfaces of joints, which are not palpable 3.3 3.7
Other clinical manifestations
Dysphagia or esophageal dysmotility Difficulty in swallowing or objective evidence of abnormal motility of the esophagus 0.7 0.6
Laboratory measurements
Anti–Jo-1 (anti–histidyl–transfer RNA synthetase) autoantibody present Autoantibody testing in serum performed with standardized and validated test, showing positive result 3.9 3.8
Elevated serum levels of CK* or LDH* or AST* or ALT* The most abnormal test values during the disease course (highest absolute level of enzyme) above the relevant upper limit of normal 1.3 1.4
Muscle biopsy features—presence of:
Endomysial infiltration of mononuclear cells surrounding, but not invading, myofibers Muscle biopsy reveals endomysial mononuclear cells abutting the sarcolemma of otherwise healthy, non-necrotic muscle fibers, but there is no clear invasion of the muscle fibers 1.7
Perimysial and/or perivascular infiltration of mononuclear cells Mononuclear cells are located in the perimysium and/or located around blood vessels (in either perimysial or endomysial vessels) 1.2
Perifascicular atrophy Muscle biopsy reveals several rows of muscle fibers, which are smaller in the perifascicular region than fibers more centrally located 1.9
Rimmed vacuoles Rimmed vacuoles are bluish by hematoxylin and eosin staining and reddish by modified Gomori trichrome stain 3.1

EULAR/ACR: European League Against Rheumatism/American College of Rheumatology, IIMs: idiopathic inflammatory myopathies, CK: creatine kinase, LDH: lactate dehydrogenase, AST: aspartate aminotransferase, ALT: alanine aminotransferase. *Serum levels above the upper limit of normal.

J Rheum Dis 2022;29:14~21 https://doi.org/10.4078/jrd.2022.29.1.14
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