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

## TL;DR

A rare case of immune disorder HLH was caused by two blood cancers in a patient, and treatment with Tocilizumab was effective.

## Contribution

This is the first reported case of HLH associated with co-existing multiple myeloma and B-cell lymphoma.

## Key findings

- HLH was driven by two distinct malignant clones in the patient's bone marrow.
- Tocilizumab led to an excellent clinical and laboratory response.
- Initial therapies like steroids and chemotherapy failed to produce results.

## Abstract

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.

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