Abstract
Exploring necrotizing autoimmune myopathies with a novel immunoassay for anti-3-hydroxy-3-methyl-glutaryl-CoA reductase autoantibodies
Drouot L, Allenbach Y, Jouen F, et al.
Arthritis Res Ther. Epub ahead of print 3 February 2014. DOI: 10.1186/ar4468.
Necrotizing autoimmune myopathy (NAM) is an emerging cause of severe statin-induced myopathy, treatable with immunosuppression, believed to result from autoantibodies (aAb) against 3-hydroxy-3-methyl-glutaryl-CoA reductase (HMGCR), the enzyme target of statins. Here the authors describe the development of an addressable laser bead immunoassay (ALBIA) to identify patients with NAM, and subsequent incorporation into a multiplex format with a previously described assay for a similar necrotizing myopathy, unrelated to statins, owing to signal recognition peptide (SRP) aAbs.
A total of 37% of 150 patients suspected to have NAM were found to have detectable anti-HMGCR aAbs, and a cutoff of 20 arbitrary units per litre had 100% sensitivity and specificity for differentiating these patients from healthy controls, as well as from patients with other autoimmune diseases. The multiplex format was able to perfectly discriminate anti-HMGCR from anti-SRP positive sera. Of note, 60% of anti-HMGCR positive patients had no prior statin exposure.
This article should raise awareness of autoimmune myopathy in statin-treated patients. It is noteworthy however, that 60% with anti-HMGCR aAbs had never received statins, as this condition was thought to be very rare in statin-naïve individuals.