Severe Polymyalgia Rheumatica-Like Syndrome Induced by Immune Checkpoint Inhibitor: A Case Report and Literature Review.

Immune checkpoint inhibitors (ICIs) have dramatically improved the prognosis of patients with cancers. However, ICIs can provoke systemic toxicities, which are known as immune-related adverse events (irAEs). Polymyalgia rheumatica (PMR)-like syndrome induced by ICI is one of the most common rheumatic irAEs. However, the management of PMR-like syndrome has not been established yet, and the optimal dose of corticosteroids remains unknown, especially for severe cases. A man in his 60s with advanced esophageal squamous cell carcinoma receiving nivolumab and ipilimumab therapy presented with a fever. Subsequently, the patient experienced bilateral femoral pain and progressive fatigue and was unable to stand within a week. The diagnosis of polymyalgia rheumatica (PMR)-like syndrome was made, and high-dose glucocorticoid therapy was started. The symptoms subsided the next day, and the corticosteroids could be quickly tapered into 10 mg over 3 weeks. The patient had sustained disease control 1 year after ICIs were discontinued. High-dose glucocorticoid therapy achieved prompt improvement of symptoms of PMR-like syndrome, even in a severe case, without compromising the anti-tumor effect of ICIs. However, the ideal treatment approach remains unknown, and prospective clinical studies are needed to determine the best strategy, especially in severe cases.