It is unclear whether polymyalgia rheumatica (PMR) should be considered an inflammatory disease or an autoimmune disease.

Eighteen untreated early PMR patients and 18 sex- and age-matched healthy controls (HCs) were included. PMR patients received tocilizumab from week 0 to week 12 and glucocorticoids from week 12 to week 24. Leukocytes, neutrophils, platelets, hemoglobin, γ-globulins, IgG, IgA, and IgM were compared between the PMR patients and HCs and before and after tocilizumab treatment in the PMR group.

The mean age was 68 ± 7 and 66 ± 11 years, and the mean serum C-reactive protein level was 82 ± 16 and 5 ± 2 mg/l for PMR patients and HCs, respectively. At inclusion, leukocytes (p < 0.0001), neutrophils (p < 0.0001), and platelets (p < 0.0001) were increased and hemoglobin (p < 0.0001) decreased in the PMR group compared to the HC group. After tocilizumab therapy, leukocytes, neutrophils, and platelets decreased, and hemoglobin increased. At inclusion, all four parameters were significantly associated with the serum IL-6 level, though it was not associated after tocilizumab therapy. Levels of γ-globulin were increased in the PMR patients compared to HCs (p = 0.0087), and PMR patients with γ-globulins levels over 11 g/l at inclusion responded more quickly to tocilizumab therapy. Autoantibody profiles did not differ between the PMR patients and HCs.

This study suggests that PMR is more an inflammatory disease than an autoimmune disease. Tocilizumab improves all markers of inflammation. Patients with elevated γ-globulins respond more quickly to tocilizumab.