Polymyalgia rheumatica (PMR) is a systemic inflammatory disorder with unknown etiology and overlapping symptoms with giant cell arthritis and rheumatoid arthritis (RA). The inflammatory pathogenesis in PMR remain poorly uncharacterized and biomarker studies very limited. The primary aim of this study was to thoroughly investigate the serum proteome and pro-/anti-inflammatory response during at debut and post-glucocorticoid treatment in comparison to DMARD-naïve RA patients, and healthy controls. Treatment naïve patients PMR patients were included and samples were obtained prior to treatment and after 3 months of treatment. Disease-modifying anti-rheumatic drug (DMARD) naïve RA patients with matched healthy controls were included for comparisons.