EULAR/ACR Classification in MDA5+ Myositis Patients Save

Sep 01, 2022 3:14 pm

The diagnosis of idiopathic inflammatory myopathies (IIMs) can be informed by the 2017 EULAR/ACR classification criteria, but their utility in patients with clinically amyopathic dermatomyositis (CADM) and anti–melanoma differentiation–associated protein 5 (anti–MDA-5)–positive IIM is less certain. A current analysis suggests that nearly 30% of MDA5 IIM patients may be missed by the 2017 EULAR/ACR classification criteria for IIM.

A total of 120 consecutive adult patients diagnosed as having anti–MDA-5–positive IIM from 10 Hong Kong hospitals were studied. One-third (31.7%) had dermatomyositis, and two-thirds (68.3%) had CADM. An IIM diagnosis was found in 72% using EULAR/ACR criteria and 41% using Bohan and Peter criteria.

The sensitivity of the EULAR/ACR criteria could be improved to 98.3% if anti–MDA-5 antibody–positive status was considered as one of the criteria. The MSA-based criteria had 100% sensitivity. With modification of specific phenotypic-serologic criteria to capture classification of patients with anti–MDA-5 antibodies, 97.5% of patients were able to be classified as having IIM.

Studies have shown the EULAR/ACR criteria had a higher sensitivity (87.7%) compared to the Bohan and Peter (BP) criteria (80.4%) and that the EULAR/ACR criteria specificity was very high (>98%) for the major IIM subgroups polymyositis, dermatomyositis, and inclusion body myositis.

In a previous report it was shown that in myositis patients with MSAs, autoantibodies outperform the EULAR/ACR-defined myositis subgroups in predicting the clinical phenotypes of patients - suggesting that MSAs should be included in future revisions of the myositis classification scheme.

These authors suggest incorporating anti–MDA-5 antibody positivity as a criterion into existing or future criteria sets to diagnose patients with IIM.

The EULAR/ACR Classification Criteria for Adult and Juvenile Idiopathic Inflammatory Myopathies and their Major Subgroups

(suggested total aggregated score of score of ≥5.5 and ≤ 5.7 (≥6.7 and ≤ 7.6 if biopsy is available)

Variable	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	1.3	1.5
Age of onset of first symptom assumed to be related to the disease ≥ 40 years	2.1	2.2
Muscle weakness
Objective symmetric weakness, usually progressive, of the proximal upper extremities	0.7	0.7
Objective symmetric weakness, usually progressive, of the proximal lower extremities	0.8	0.5
Neck flexors are relatively weaker than neck extensors	1.9	1.6
In the legs proximal muscles are relatively weaker than distal muscles	0.9	1.2
Skin manifestations
Heliotrope rash	3.1	3.2
Gottron´s papules	2.1	2.7
Gottron’s sign	3.3	3.7
Other clinical manifestations
Dysphagia or esophageal dysmotility	0.7	0.6
Laboratory measurements
Anti-Jo-1 (anti-histidyl-tRNA synthetase) autoantibody present	3.9	3.8
Elevated serum levels of creatine kinase (CK)^* or lactate dehydrogenase (LDH)^* or aspartate aminotransferase (ASAT/AST/SGOT)^* or alanine aminotransferase (ALAT/ALT/SGPT)^*	1.3	1.4
Muscle biopsy features- presence of:
Endomysial infiltration of mononuclear cells surrounding, but not invading, myofibres		1.7
Perimysial and/or perivascular infiltration of mononuclear cells		1.2
Perifascicular atrophy		1.9
Rimmed vacuoles		3.1