Checkpoint inhibitor immunotherapy induced inflammatory arthritis secondary to Nivolumab and Ipilimumab: a pediatric first

Immune checkpoint inhibitors (ICIs) have expanded the arsenal of cancer therapeutics over the last decade but are associated with a spectrum of immune-related adverse events (irAEs), including inflammatory arthritis. While these complications are increasingly recognized in the adult population, no cases of inflammatory arthritis irAEs have been reported in the pediatric literature. A 14-year-old female with metastatic epithelioid mesothelioma was referred to the pediatric rheumatology clinic after developing progressive inflammatory joint pain in her bilateral shoulders, hips, and small joints of hands following the second cycle of Nivolumab and Ipilimumab. Initial examinations showed bilateral shoulder joint line tenderness, positive FABERs test bilaterally, tenderness over bilateral greater trochanters, and bilateral second PIP effusions. Her serological profile was notable for positive HLA-B27, positive anti-CCP, negative Rheumatoid Factor, and negative ANA. PET-CT scan performed for disease response following immunotherapy showed symmetric increased metabolic activity primarily involving the supraspinatus, gluteus medius and minimus, and semimembranosus tendon insertions. Her presentation was consistent with a grade 1 irAE that worsened to a grade 2 irAE despite NSAID therapy, prompting a short course of oral prednisolone. She achieved clinical remission of her mesothelioma following six cycles of Nivolumab and Ipilimumab and her inflammatory arthritis was controlled on Celebrex monotherapy. To our knowledge, this is the first pediatric case of ICI-induced inflammatory arthritis and enthesitis. This case highlights the importance of increasing awareness of diagnosis and management of irAEs in children.