Abstract
Hemophagocytic lymphohistiocytosis (HLH) is a rare hyperinflammatory state that leads to overactivation of the immune system due to underlying disease. It can lead to multiorgan failure and death if not treated properly. HLH after vaccination is rare but has been reported in a few cases. Here, we present a case of a patient who developed HLH after she received the COVID-19 vaccine. Workup was done to find the underlying cause of her symptoms. However, as all investigations yielded negative results, the close temporal association with the COVID-19 vaccine suggested that the vaccine might have been the causative factor. She was treated appropriately with steroids and discharged with follow-up appointments. The exact pathogenesis of HLH caused by COVID vaccine is unknown, but it is likely related to the inflammatory response caused by the vaccine in the body. The treatment of HLH depends on the treatment of underlying conditions causing the HLH. Very few cases have been reported in the literature regarding HLH caused by COVID vaccine. Immediate recognition and treatment are imperative for improved prognosis and improved chances of survival.