Spectrum of immune-mediated necrotizing myopathies and their treatments.
OBJECTIVE
This review aims to describe the spectrum of clinical, histological, and serological features in patients with immune-mediated necrotizing myopathies (IMNMs).


RESULTS
Autoantibodies recognizing the signal recognition particle (SRP) or 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) define two unique subtypes of necrotizing myositis patient with distinct clinical features. For example, the major histocompatibility class II human leukocyte antigen allele DRB111:01 is a strong immunogenetic risk factor for developing anti-HMGCR autoantibodies whereas B5001 and DQA10104 are over-represented in patients with anti-SRP autoantibodies. Furthermore, statin exposure is a risk factor only for anti-HMGCR autoantibodies. And while skeletal muscle involvement is predominant in most patients with both autoantibodies, lung involvement appears in ∼20% of anti-SRP-positive patients but is more rare in anti-HMGCR-positive patients. Of note, ∼20% of anti-SRP and anti-HMGCR positive patients have significant lymphocytic infiltrates on muscle biopsy and thus would not be formally categorized as having IMNM; aside from this, these patients are clinically indistinguishable from other patients with the same autoantibody profile.


CONCLUSIONS
Anti-SRP and anti-HMGCR autoantibodies define unique populations of IMNM patients. It may be more appropriate to subtype myositis patients based on these autoantibodies than on their muscle biopsy features.
aNational Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda bJohns Hopkins University School of Medicine, Baltimore, Maryland, USA.
Iago
I
Pinal-Fernandez
Andrew L
AL
Mammen
D000214:Acyl Coenzyme A; D001323:Autoantibodies / Q000097:blood; D001327:Autoimmune Diseases / Q000139:chemically induced / Q000175:diagnosis* / Q000276:immunology; D001706:Biopsy; D006801:Humans; D006903:Hydroxymethylglutaryl CoA Reductases / Q000276:immunology; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000009:adverse effects; D018482:Muscle, Skeletal / Q000473:pathology; D009220:Myositis / Q000139:chemically induced / Q000175:diagnosis* / Q000276:immunology; D009336:Necrosis; D018271:Signal Recognition Particle / Q000276:immunology
D000214:Acyl Coenzyme A; D001323:Autoantibodies; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D018271:Signal Recognition Particle; C008047:3-hydroxy-3-methylglutaryl-coenzyme A; D006903:Hydroxymethylglutaryl CoA Reductases