LAUSR

Immune checkpoint inhibitors (ICIs) are increasingly being used in oncology and there is growing evidence of rheumatological problems arising in these group of patients. ICIs have been approved for the treatment of several cancers including non-small cell lung cancer, renal cell carcinoma, Hodgkin lymphoma and other malignancies. Pembrolizumab, an anti-PD1, is known to cause inflammatory arthritis in some patients, and we report a case of relapsing-remitting synovitis with pedal oedema (RS3PE) in a patient with lung cancer. A 67-year-old lady was diagnosed with adenocarcinoma in her left lung with pleural and pulmonary metastasis. She was commenced on carboplatin, pemetrexed and pembrolizumab initially for 4 cycles followed by pembrolizumab maintenance therapy for another 2 years. However, while on pembrolizumab therapy, she started to develop intermittent pain and swelling in her small joints of the hands and feet. There was marked pitting pedal oedema extending up to the knee along with swelling of the dorsum of the hand. She had intermittent swelling in the knee joints as well. The blood tests were negative for rheumatoid factor, anti-CCP and ANA. The CRP was markedly raised (120) from her previous values since she started developing joint symptoms. The kidney and liver function tests were within normal limits. A CT chest, abdomen pelvis was done which did not reveal any metastasis or progression of lung cancer. At the time of the review she was started on prednisolone 20mg once daily. Following this, the joint pain and swelling started to resolve, and the patient was advised to taper the steroids gradually. The pembrolizumab therapy was stopped few months later. The pedal oedema resolved within a few weeks of starting steroids and the joint inflammation settled after stopping the treatment. ICI therapy has been known to trigger inflammatory arthropathy like RA. Psoriatic arthritis, undifferentiated monoarthritis and oligoarthritis, RS3PE and tenosynovitis have also been reported. Most published cases are mild to moderate in severity often responding to corticosteroids. Several patients have been treated with traditional DMARDs and biologics. RS3PE syndrome could be part of the paraneoplastic process but the onset of symptoms after starting pembrolizumab and rapid resolution after stopping the treatment indicates that this is likely a drug-induced adverse effect. Disclosure D. Ramachandran: None. W. Mushtaq: None. D. Makkuni: None.