Seronegative patients form a distinctive subgroup of immune-mediated necrotizing myopathy
2019
Objectives To investigate the characteristics of different clinico-serologic subgroups of immune-mediated necrotizing myopathy (IMNM). Methods We retrospectively reviewed data from medical charts of 64 patients diagnosed with IMNM between 2012 and 2017 in 3 neuromuscular referral centers in The Netherlands and 1 in Belgium. Results Seventeen patients had anti-
3-hydroxy-3-methylglutaryl-coenzymeA reductase (HMGCR) autoantibodies (
Abs), of whom 11 had a history of statin use, 15 had anti-
signal recognition particle(SRP)
Abs, 2 had anti-melanoma
differentiation-associatedprotein 5 (
MDA5)
Abs, 22 patients were seronegative, and 9 patients did not have a complete
Abassessment. Moderate to severe disability in HMGCR
Ab–positive and anti-SRP
Ab–positive IMNM was common (71% and 60%, respectively) despite multimodality treatment. Compared with statin-associated anti-HMGCR
Ab–positive IMNM, statin-naive anti-HMGCR
Ab–positive IMNM patients were more often men (67% vs 45%), had lower rates of dysphagia (17% vs 45%), and more frequently had
third-line therapy(50% vs 9%) and poor to fatal outcome (50% vs 0%). Compared with seropositive IMNM, seronegative IMNM was characterized by female predominance (1:3), frequent occurrence of associated connective tissue disorders (22% vs 9%), and significantly higher rates of extramuscular disease activity (50% vs 16%, p 0.014;
2-sidedFisher exact), also after excluding patients with an associated
connective tissue disease(35% vs 7%, p 0.038;
2-sidedFisher exact). Conclusions Our findings indicate that seronegative IMNM forms a subgroup with distinctive features from seropositive IMNM.
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