(Kiosk 1) Pembrolizumab-induced Inflammatory Arthritis: A Case Report

Case Diagnosis: Pembrolizumab-induced inflammatory arthritis

Case Description: A 50-year-old female with history of vitiligo, chemotherapy-induced hypothyroidism, and invasive ductal carcinoma of the left breast (cT2N0Mx, near triple negative) status post bilateral skin sparing mastectomy with reconstruction and post-mastectomy radiation presented to clinic with one year of progressively worsening diffuse joint pain. Patient completed neo-adjuvant chemotherapy with ddAC-T (dose-dense Adriamycin, Cytoxan, Taxol) and pembrolizumab and was briefly on anastrozole. Patient developed migratory joint pain few months after starting on pembrolizumab which did not resolve with discontinuation of the medication. Pain is the worst in her hands and feet with numbness and swelling. She did see improvement of pain with meloxicam.

Discussion: Pembrolizumab is a PD-1 inhibitor that enhances T-cell activation, often leading to immune-related adverse events (irAEs). Arthralgia and myalgia are the most reported irAEs in clinical trials. Some patients may develop classic rheumatic and musculoskeletal diseases (RMDs) while others may have mimic of RMDs. Given diffuse joint pain and inflammation with markedly elevated ANA, Raynaud's phenomenon, sclerodactyly and pre-existing vitiligo in the setting of treatment with pembrolizumab, patient’s presentation is most consistent with a pembrolizumab-induced inflammatory arthritis.

Setting: outpatient clinic

Assessment/Results: Physical exam was notable for bilateral hands and feet swelling with Raynaud’s and sclerodactyly of her fingers. Also, skin color changes consistent with vitiligo were seen on bilateral hands. Finger joints, wrists, and toes were tender to palpation and range of motion was limited in the fingers and wrists. Recent imaging showed wrist synovitis, tenosynovitis of flexor and extensor tendons, and osteoporosis. Labs revealed markedly elevated antinuclear antibodies (ANA). Patient was recommended a further workup with a rheumatologist and was prescribed celecoxib for pain.

Conclusion: With expanding use of checkpoint inhibitors, more cancer patients are developing RMDs and RMD mimics. It is important for physiatrists to recognize these side effects and refer patients to appropriate specialists.