Immune checkpoint inhibitor-mediated polymyalgia rheumatica versus primary polymyalgia rheumatica: comparison of disease characteristics and treatment requirement

Abstract Objectives To compare clinical characteristics, imaging findings and treatment requirements of patients with immune checkpoint inhibitor-mediated polymyalgia rheumatica (ICI-PMR) and primary PMR. Methods This single centre, retrospective cohort study compared ICI-PMR in patients with cancer (n = 15) to patients with primary PMR (n = 37). A comparison was made between clinical symptoms, laboratory markers, ultrasonography, 18F-FDG-PET/CT findings and treatment requirements related to PMR. Results Patients with ICI-PMR less frequently fulfilled the EULAR/ACR classification criteria for PMR (66.7%) than patients with primary PMR (97.3%). Morning stiffness, weight loss and elevation of the ESR were less frequently seen in patients with ICI-PMR. No differences were observed regarding the presence of inflammatory lesions on ultrasound of the shoulders and hips between the two groups. The Leuven and the Leuven/Groningen 18F-FDG-PET/CT scores were significantly lower in the ICI-PMR group. Finally, the ICI-PMR group could be managed with lower glucocorticoid doses than the primary PMR group, while this treatment could be discontinued more quickly. Conclusion Our findings indicate that ICI-PMR may have a milder course with less intense inflammation than primary PMR. ICI-PMR can be managed with a relatively low glucocorticoid dose. Our study underscores that ICI-PMR should be regarded as a PMR-like syndrome.