Low-volume plasma exchange and low-dose steroid to treat secondary hemophagocytic lymphohistiocytosis: A potential treatment for severe COVID-19?

Secondary hemophagocytic lymphohistiocytosis (sHLH) may be responsible for some of the deaths in adult patients with severe COVID-19. We present our experience of low-volume plasma exchange (PLEX) with low-dose steroid in the treatment of adult patients with sHLH and acute liver failure caused by dengue virus and other nonviral triggers and discuss how this may be effective in the management of severe COVID-19. sHLH is poorly understood and without effective treatment. Endothelium of the capillaries of the lungs and kidneys and of liver sinusoids does not express von Willebrand factor (VWF) in health and is where most macrophages are located. Plasma VWF levels are high in sHLH and require clearance by macrophages, which when activated enlarge and likely block the lumen. Current histology studies neither appreciate microcirculatory sludge nor display endothelial–macrophage interactions. We hypothesize that low-volume PLEX and low-dose steroid may reverse sHLH and improve survival in severe COVID-19 patients with acute lung injury.