Anti-CADM-140/MDA5 autoantibody titer correlates with disease activity and predicts disease outcome in patients with dermatomyositis and rapidly progressive interstitial lung disease.

OBJECTIVES

We examined the relationship between disease activity and anti-CADM-140/MDA5 titer measured by enzyme-linked immunosorbent assay (ELISA).

METHODS

Sera from 63 patients with dermatomyositis (DM) [46 classic DM, 17 clinically amyopathic DM (CADM)] were screened for autoantibody using immunoprecipitation assay. Anti-CADM-140/MDA5-positive sera were examined for their titer by anti-CADM-140/MDA5 ELISA. Potential associations between anti-CADM-140/MDA5 titer and clinical course or outcome were analyzed.

RESULTS

Sera from 14 patients with DM (2 classic DM, 12 CADM) had anti-CADM-140/MDA5. Of ten patients with DM and rapidly progressive interstitial lung disease (RP-ILD), the mean titer of anti-CADM-140/MDA5 before treatment was significantly lower in patients who responded to therapy and survived (responder group, n = 4) than in those who did not respond and died (nonresponder group, n = 6) (110.3 vs. 356.9, P = 0.019). In the responder group, the mean titer of anti-CADM-140/MDA5 significantly decreased down to below the cutoff level after treatment (n = 3, 113.4 vs. 1.6, P = 0.033), whereas that of the nonresponder group did not decrease sufficiently and sustained high level (n = 4, 372.5 vs. 198.4, P = 0.31).

CONCLUSIONS

These results emphasize the clinical importance of anti-CADM-140/MDA5 antibody levels to predict outcomes of RP-ILD as well as to monitor disease activity in patients with DM and RP-ILD.