Polymyalgia rheumatica with normal inflammatory indices at the time of diagnosis: can we just move a step forward?

The existence of polymyalgia rheumatica (PMR) with normal inflammatory indices at the time of diagnosis still represents a diagnostic conundrum. According to the literature, some patients with PMR following immune checkpoint inhibitory therapy had normal values of both erythrocyte sedimentation rate and C-reactive protein concentrations at the time of diagnosis. In this short communication we investigated the possibility that in some patients with PMR the main pathogenic mechanism is constituted by inhibition of some checkpoints, such as programmed death receptor-1, programmed death ligand 1, and “cytotoxic” lymphocyte antigen 4. In these patients, the pathogenetic mechanisms underlying PMR can act much more upstream than commonly suggested. Also, we addressed the question of whether these patients should be considered as affected by PMR-like syndromes or by PMR subset.