[Grand Round] Haemophagocytic lymphohistiocytosis (HLH) secondary to measles in an adult with a loss of post-vaccination humoral immunity following rituximab

Measles is an important re-emergent infectious disease globally. Vaccine immunity at the population level is key to the prevention of outbreaks, as unvaccinated or immunosuppressed adults are particularly vulnerable to severe infection. With the increasing use of immunomodulatory treatments for autoimmune and malignant conditions, the long-term effects of CD20-expressing cell-depleting therapies on the vaccine-induced humoral immunity to measles remain unclear. Haemophagocytic lymphohistiocytosis (HLH) is a hyperinflammatory syndrome with high mortality commonly triggered by infection and is possibly under-reported in association with measles.