COVID-19 vaccination-related hemophagocytic lymphohistiocytosis presenting as acute liver failure.

Acute liver failure following COVID-19 infection and/or vaccination is very rare and can be secondary to hemophagocytic lymphohistiocytosis (HLH). Liver injury in such cases appears to be extrinsic and thus treatment hinges on prompt diagnosis and reversal of the primary disease. We describe a patient who developed acute liver failure secondary to HLH after receiving a second dose of the Pfizer COVID-19 vaccine. Persistently elevated liver function tests, fevers, and cytopenia following COVID-19 vaccination should prompt clinicians to calculate an H-score to evaluate for the presence of HLH.