Secondary Hemophagocytic Lymphohistiocytosis in a Post-COVID-19 Patient.

Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening condition caused by excessive immune system activation. HLH can be primary or secondary. Primary HLH is commonly seen in children with underlying genetic mutations, while secondary HLH can be seen at any age. It is usually triggered by inciting factors such as viral infections, patients with underlying rheumatological disease, or malignancies. It has very poor prognosis if left untreated, with survival of only a few months. While there have been around 100 cases of HLH reported during the acute phase of COVID-19 infection, very few post-COVID-19 HLH cases have been reported, only around 35 cases. Here we report a case of a 20-year-old Caucasian male who presented eight weeks after COVID-19 infection with extreme fatigue, fever, lab work concerning for HLH, and a high H score indicating a high probability of HLH. Early identification of HLH following COVID-19 recovery would allow for timely management of the condition.