Hemophagocytic lymphohistiocytosis due to pembrolizumab therapy for adenocarcinoma of the lung.

Hemophagocytic lymphohistiocytosis (HLH) is a rare disorder of dysregulated inflammation. It is most commonly seen in children who have a predisposing genetic mutation. However, adults can contract an acquired version of the disorder secondary to an infectious, neoplastic, or other inflammatory insult. There have been several documented cases of HLH being induced by treatment with immunotherapy. Here, we present the case of a 71-year-old man who was receiving pembrolizumab for lung adenocarcinoma when he developed HLH following his 14th cycle of therapy. Although bone marrow biopsy was negative, he nevertheless fulfilled the diagnostic criteria of the HLH 2004 report and was treated with high-dose steroids followed by a prolonged taper, with resolution of his symptoms and normalization of his blood counts.