Hemophagocytic Lymphohistiocytosis as First Manifestation of Dual B‐Cell Neoplasms: A Case Report of Co‐Existing Multiple Myeloma and B‐Cell Lymphoma

Hemophagocytic lymphohistiocytosis (HLH) is an immune disorder causing excessive inflammation and tissue damage. Lymphoma, especially T-cell lymphoma, is the most common cause of HLH, while Multiple Myeloma (MM) is rarely associated. We present a 61-year-old man with spiking fevers, fatigue, and unintentional weight loss. The HLH was driven by two distinct malignant clones in his bone marrow: plasma cell neoplasm and B-cell lymphoma. Patient failed initial therapy with steroids, anakinra, and chemotherapy. Tocilizumab use, on the other hand, led to an excellent clinical and laboratory response immediately. This is the first reported case of HLH associated with two hematological malignancies. <b>Trial Registration</b>: The authors have confirmed clinical trial registration is not needed for this submission.