Persistent Fever after COVID-19 Vaccination in a Patient with Ulcerative Colitis: A Call for Attention

The development of vaccinations has been game-changing in the ongoing effort to combat the COVID-19 pandemic. Until now, adverse effects are being reported at low frequency, including thrombocytopenia and myocarditis. Careful monitoring for any suspicious symptoms and signs following vaccination is necessary. We report a case of hemophagocytic lymphohistiocytosis (HLH) after mRNA COVID-19 vaccine in a 23-year-old female with ulcerative colitis. Diagnosis was made according to HLH-2004 criteria and the patient was treated with dexamethasone with response. Our report aimed to draw attention to the potential relation between COVID-19 vaccines and HLH and the necessity of continued surveillance, especially in at-risk populations such as those with underlying immune dysregulation.