Anti-cortactin autoantibodies are associated with key clinical features in adult myositis but are rarely present in juvenile myositis.

Objective To define the prevalence and clinical phenotype of anti-cortactin autoantibodies in adult and juvenile myositis. Methods In this longitudinal cohort study, anti-cortactin autoantibody titers were assessed by ELISA in 670 adults and 343 juvenile myositis patients as well as 202 adult and 90 juvenile healthy controls. The prevalence of anti-cortactin autoantibodies was compared among groups. The clinical features of patients with and without anti-cortactin autoantibodies were also compared. Results Anti-cortactin autoantibodies were more common in adult dermatomyositis (DM) patients (15%, p=0.005), particularly those with co-existing anti-Mi-2 (24%, p=0.03) or anti-NXP2 (23%, p=0.04) autoantibodies. In adult myositis, anti-cortactin was associated with DM skin involvement (62% vs. 38%, p=0.03), dysphagia (36% vs. 17%, p=0.02) and co-existing anti-Ro52 (47% vs. 26%, p=0.001) or anti-NT5C1a autoantibodies (59% vs. 33%, p=0.001). Moreover, the titers of anti-cortactin antibodies were higher in patients with interstitial lung disease (0.15 vs. 0.12 arbitrary units, p=0.03). The prevalence of anti-cortactin autoantibodies was no different in juvenile myositis (2%) or any juvenile myositis subgroup compared to juvenile healthy controls (4%). Nonetheless, juvenile myositis patients with these autoantibodies had a higher prevalence of mechanic's hands (25% vs. 7%; p=0.03), a higher number of hospitalizations (2.9 vs. 1.3, p=0.04), and lower peak CK values (368 vs. 818 IU/L, p=0.02) CONCLUSIONS: The prevalence of anti-cortactin autoantibodies is increased in adult DM patients with co-existing anti-Mi-2 or anti-NXP2 autoantibodies. In adults, anti-cortactin autoantibodies are associated with dysphagia and interstitial lung disease.