Immune checkpoint inhibitor-associated arthritis in advanced pulmonary adenocarcinoma: A case report

BACKGROUND: With the wide application of immune checkpoint inhibitors (ICIs) in cancer treatment, immune-related adverse events occur frequently, involving almost all organs and systems. The incidence of ICI-associated arthritis (IA) is unknown. In most cases, IA is not serious and non-lethal. Higher checkpoint inhibitor arthritis disease activity may be associated with cancer progression. Here, we report a severe case of IA with high arthritis disease activity in advanced pulmonary adenocarcinoma, causing permanent withdrawal of pembrolizumab, but the patient remained in complete remission (CR) 20 mo after the development of IA. CASE SUMMARY: An 81-year-old smoking man was admitted to our hospital because of left chest pain for 9 mo. He was finally diagnosed with advanced pulmonary adenocarcinoma, with programmed cell death 1 ligand 1 expression of 70%. The patient responded to pembrolizumab treatment and achieved CR, but IA occurred after the 5(th )cycle of pembrolizumab administration. Although non-steroidal anti-inflammatory drugs and disease-modifying anti-rheumatic drugs were prescribed, arthralgia and joint swelling occurred. The symptoms of arthritis were further aggravated when immunotherapy was given again after short-term withdrawal. Clinical Disease Activity Index (CDAI) score, a traditional measure of arthritis activity, was 43. Intravenous methylprednisolone was prescribed at 20 mg/d and then tapered over the subsequent 4 wk. The symptoms of arthritis steadily improved and completely resolved 4 mo after withdrawal of pembrolizumab. A recent follow-up in June 2022 revealed satisfactory clinical recovery of arthritis and the patient remained in CR. CONCLUSION: This case report highlights that early recognition of IA and appropriate treatment are critical to improving the outcome of both ICI-arthritis and lung cancer.