Synchronous brain and intravascular B‐cell lymphoma after remission of an adult hemophagocytic syndrome

Hemophagocytic lymphohistiocytosis (HLH) 1 is a rare and life‐threatening hyperinflammatory syndrome caused by genetic mutations (primary HLH) or systemic acquired conditions (secondary HLH) which in adults is most commonly associated with hematological malignancies 2, 3. Although primary and secondary HLH have usually been considered distinct entities, recent evidence has pointed to an increase in the frequency of heterozygous mutations in PRF1, UNC13D, and STXBP2 genes, suggesting an increased overlap between the two forms of the disease 4. The central nervous system (CNS) is commonly affected in children with HLH where white matter abnormalities are characteristic 5. In adults, neurological manifestations have been reported in up to 25% of cases 1, 2, although HLH is not usually considered in the differential diagnosis of white matter abnormalities in this age group. We report an adult hemophagocytic syndrome presenting like a primary HLH with a good response to therapy that evolved subsequently to a unique form of diffuse large B‐cell lymphoma with fulminant CNS involvement and concomitant intravascular lymphoma (IVL).