We present an extremely rare case report of a 29-year-old multiple myeloma patient with central nervous system involvement and secondary hemophagocytic lymphohistiocytosis (HLH). We observed that HLH was presumably triggered by the immunomodulatory drug—lenalidomide. HLH is frequently misdiagnosed or underdiagnosed. As HLH requires immediate treatment, our report emphasizes the need to consider HLH in the differential diagnosis when the condition of a patient receiving chemotherapy rapidly deteriorates and an infectious etiology is excluded. We furthermore discuss the pathogenesis of HLH, with particular emphasis on drugs affecting the immune system as well as possible therapeutic strategies.
