Introduction
HLH is a rare, life-threatening pediatric condition characterized by uncontrolled hyperinflammation caused by various hereditary or acquired immune deficiencies. It is classified into two subgroups: Primary HLH including familial HLH (FHLH) and immunological deficits and secondary HLH which can be caused by infection, cancer, rheumatology, or iatrogenic factors (transplantation, immunological suppression, immune stimulation).
HLH is always fatal unless treatment results in a partial or total clinical response. Chemo-immunotherapy with steroids, etoposide, and cyclosporine, as well as rabbit antithymocyte globulin, cyclosporine, and prednisone, can be used with or without intrathecal methotrexate. So far, the only curative therapy strategy is allogeneic hematopoietic stem cell transplantation.
Central nervous system (CNS) involvement, has been documented as an independent risk factor for mortality in children with HLH. Clinically, due to the rarity of pathological studies of HLH, making the diagnosis of CNS involvement difficult, clinicians must rely on clinical manifestations combined with imaging and laboratory tests to confirm such diagnosis.