Background Making the diagnosis of adult-onset Still’s disease (AOSD) is mainly based on the exclusion of inflammatory, infectious and malignant diseases. There are no specific clinical or laboratory findings for AOSD. Elevated ferritin levels, liver enzyme levels, C-reactive protein levels, erythrocyte sedimentation rate and leukocytosis can be found in other inflammatory diseases as well.

Objectives We aimed to identify new autoantibodies as diagnostic tools for AOSD.

Methods We were studying sera of 3 patients with AOSD using a protein array loaded with more than 27000 human recombinant proteins (imagenes biolifesciences, Berlin). Sera of patients with SpA, RA, eGPA, GPA, HIV infection, B-NHL, CRPS, GCA, PMR, MS, osteoarthritis, TA and sarcoidosis served as controls.

In the further process, we established an ELISA against a new autoantigen identified by the array in order to measure the autoantibodies in larger patient numbers.

Results Using the protein array, we detected IgG autoantibodies binding to Dihydropyrimidinase-related protein 4 (DRP-4) (collapsin response mediator protein 3) and in 2/3 patients with AOSD IgG autoantibodies binding to proteasome subunit alpha type-1 (EC 3.4.25.1) (proteasome component C2) (macropain subunit C2) (multicatalytic endopeptidase complex subunit C2) in 2/3 AOSD patients, but not in more than 50 controls.

Using the ELISA, we detected Auto-Abs binding to Macropain subunit C2 and DRP-4 in 65% of the patients with AOSD, in 0.7 % of blood donors, 9.1% of RA patients with RA, 10% of GPA patients, 22% of the patients with PMR and GCA, 3.4% of the patients with Sjögren’s syndrome, 10.5% of the SLE patients, 21% of the patients with febrile severe infections and in 0.7% of the patients with malignant diseases.

Conclusions Autoantibodies against DRP-4 and Macropain C2 are associated with AOSD and may be useful as a diagnostic tool of AOSD.

Disclosure of Interest None Declared