Background/Purpose:

To investigate the occurrence of anti-calreticulin antibodies (anti-CRT Abs) and evaluate its association with malignancy in patients with idiopathic inflammatory myopathies (IIM).

Methods:

In total, 211 patients with IIM were enrolled in our study and patients complicated with malignancy were separated into a single category. The levels of anti-CRT Abs were measured in serum samples from 106 with dermatomyositis (DM), 21 with polymyositis (PM), 34 with immune-mediated necrotizing myositis (IMNM), 50 IIM with malignancy and 40 healthy controls (HC) by an in-house enzyme-linked immunosorbent assay (ELISA) using recombinant full-length CALR. The clinical and laboratorial data were collected and compared between anti-CRT Abs positive and negative patients. Then 8 IIM patients were followed longitudinally whose changes in concentrations of anti-CRT Ab were assessed and variations in disease activity were measured by myositis disease activity assessment visual analog scales (MYOACT) scores. Receiver operating characteristic (ROC) curve analysis was performed to determine the value of anti-CRT Abs in distinguishing IIM with malignancy from those without malignancy.

Results:

Serum levels of anti-CRT Abs were significantly higher in IIM [median 5.3 AU (IQR 2.5-11.6)] than in HC [median 3.8 AU (IQR 1.8-6.4), P = 0.003] and anti-CRT Abs were judged to be positive in 48 of 211 IIM patients (22.7%). Among the IIM subgroups, 17/106 (16.1%) DM, 2/21 (9.5%) PM, 7/34(20.6%) IMNM and 22/50 (44%) IIM with malignancy were seropositive for anti-CRT Abs. Higher frequency of malignancy, heliotrope rash and gottron papules as well as elevated concentrations of immunoglobulin G (IgG) and anti-nuclear Abs (ANA) were present in IIM patients with positive anti-CRT Abs than in those negative. A positive correlation between serum anti-CRT Abs concentrations and MYOACT scores was shown by longitudinal study. ROC curve analysis revealed that the anti-CRT Abs had diagnostic value in distinguishing IIM with malignancy from those without malignancy, with an area under curve (AUC) value of 0.65 (95% CI 0.56 – 0.74, P= 0.001).

Conclusion:

This is the first report to discover that anti-CRT Abs could be a novel autoantibody detected in IIM. The levels of anti-CRT Abs increased significantly and markedly high anti-CRT Abs levels could be a possible serological marker of malignancies in IIM patients.

« Back to 2018 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/anti-calreticulin-antibody-a-novel-antibody-in-patients-with-idiopathic-inflammatory-myopathies-and-its-association-with-malignancy/