Haemophagocytic Lymphohistiocytosis Following the anti-PD-1 Nivolumab in a Patient with Gastric Cancer and Ankylosing Spondylitis.

Background: Autoimmune diseases are not contraindications for immune checkpoint inhibitors (ICI) therapy in patients with cancer. However, immune-related adverse events (irAEs) are frequently observed in patients receiving ICIs including dermatitis, thyroiditis, colitis, and pneumonitis. Thrombocytopenic purpura, aplasia, and haemophagocytic lymphohistiocytosis (HLH) are rarely observed during ICIs. Case description: We report the case of a male patient with pre-existing untreated HLA B27 and ankylosing spondylitis with gastric cancer and liver metastases. The 79-year-old man was treated with anti-HER2 trastuzumab and anti-PD-1 nivolumab. Seventeen days after the seventh cycle of treatment, he presented at the emergency department with acute fever, confusion, and hypotension. Laboratory results showed pancytopenia, and elevation of ferritin and triglyceride. No infections were detected. Although not seen in a bone marrow biopsy, clinical presentation, and absence of infection, together with an H-score of 263, indicated HLH. The patient was treated with dexamethasone for four days and discharged on a tapering dose of steroids. At the two-month follow-up, clinical presentation was normal and blood test almost normalised. At 8 months, no liver metastases were observed. Conclusions: In a patient with a pre-existing autoimmune condition, immunotherapy led to the development of HLH, which was controlled by glucocorticoid. Absence of the feature of haemophagocytosis in the bone marrow biopsy did not exclude the diagnosis, as HLH can occur in the spleen or in the liver. Glucocorticoid therapy did not prevent the anti-cancer effect of ICIs, and liver metastases disappeared 8 months post-HLH. This case warrants further research on the interplay between autoimmunity and ICI response, as well as ICI-induced irAEs. LEARNING POINTS: Haemophagocytic lymphohistiocytosis (HLH) post seventh cycle of trastuzumab (anti-HER2) and nivolumab (anti-PD-1) was controlled with glucocorticoid.Breach of tolerance was due to immunotherapy-induced HLH in a patient with pre-existing autoimmune condition (HLA B27- positive ankylosing spondylitis).There was a complete disappearance of liver metastases 8 months post-HLH.