# Malignancy-Associated Secondary Hemophagocytic Lymphohistiocytosis Mimicking an Infection: A Case Report and Review of the Literature

## TL;DR

A child with a rare immune disorder initially thought to be an infection was found to have cancer, highlighting the need for early suspicion of malignancy in similar cases.

## Contribution

This case report highlights the diagnostic challenge of malignancy-associated hemophagocytic lymphohistiocytosis mimicking infection.

## Key findings

- The patient's symptoms and lab results were consistent with hemophagocytic lymphohistiocytosis.
- Lymph node biopsy confirmed anaplastic large cell lymphoma as the underlying malignancy.
- Treatment with dexamethasone and chemotherapy led to clinical remission.

## Abstract

Hemophagocytic lymphohistiocytosis (HLH) is a rare, life-threatening hematological disorder of immune dysregulation associated with significant challenges in diagnosis and management. Described as primary HLH secondary to genetic defects or more commonly secondary to infections, it can also occur secondary to malignancy, i.e., malignancy-associated hemophagocytic lymphohistiocytosis (M-HLH).

A five-year-old male child presented with left cervical adenopathy and a high-spiking fever for two weeks. He had pallor, anasarca, multiple enlarged and matted cervical lymph nodes, respiratory distress, and hepatomegaly. He had continuous high-grade fever spikes (maximum 105 °F), not touching baseline despite broad-spectrum antibiotics. The CBC revealed anemia with thrombocytopenia. Liver function tests showed mild transaminitis and hypoalbuminemia. The HLH workup showed elevated ferritin, low fibrinogen, and elevated triglycerides. Lymph node biopsy showed intermediate to large atypical monomorphic lymphocyte cells with ALK, CD30, CD5, CD3, CD45, and BCL-2 (weak positive) positivity and Ki-67-95%, suggestive of anaplastic large cell lymphoma (ALCL). The bone marrow aspiration showed reactive marrow with hemophagocytosis.

The patient was started on dexamethasone and chemotherapy per the Children's Oncology Group's (COG) ALCL protocol. He showed remarkable clinical improvement and went into remission after the induction phase. Malignancy associated with HLH can mimic infection, as in our patient with high-spiking fever, consolidation, and mediastinal adenopathy. A high index of suspicion is necessary to arrive at an appropriate, early diagnosis, and workup for malignancy is to be considered when an infectious etiology is not identified after thorough evaluation.