Secondary HLH (Hemophagocytic Lymphohistiocytosis): An ultra-short case report

Harish Mallapura Maheshwarappa*

Director – Institute of Critical Care Medicine. Kauvery Hospital, Bengaluru

*Correspondence: M: +918095218493; Email: https://harishcriticalcareclasses.com

Introduction

Hemophagocytic Lymphohistiocytosis (HLH) is a rare but potentially life-threatening hyper-inflammatory condition characterized by excessive immune activation. It can be primary (genetic) or secondary to infections, malignancies, or autoimmune diseases. This case report presents a rare instance of secondary HLH triggered by dengue fever.

Case Presentation

A 30-year-old woman, a mother of two with  background of hypothyroidism,presented with a ten-day history of fever associated with myalgia and weakness. She was initially diagnosed with dengue fever with thrombocytopenia at an outside hospital. Despite initial management, she developed severe complications and was transferred to our intensive care unit (ICU).She was admitted to our ICU with persistent fever, severe pancytopenia, and multiple organ dysfunction including acute respiratory distress syndrome, polyserositis, and acute liver injury.

Clinical Findings

Upon admission, the patient was febrile and showed signs of acute respiratory distress syndrome (ARDS), polyserositis, and acute liver injury. Physical examination revealed splenomegaly and generalized weakness.

Laboratory Investigations

  • Total Bilirubin – 8 mg/dL
  • Liver Enzymes – 6000 U/L
  • Coagulopathy – Present
  • Ferritin – 118,000 ng/mL
  • Triglycerides – >1500 mg/dL
  • Lactate Dehydrogenase (LDH) – >30,000 U/L

These findings raised the suspicion of HLH.

Diagnostic Criteria

According to the HLH-2004 diagnostic guidelines, a diagnosis can be made if five out of the following eight criteria are met:

Fever: Persistent fever ≥ 38.5°C.

Splenomegaly: Enlarged spleen.

Cytopenias: Affecting at least two of three lineages in the peripheral blood:

  • Hemoglobin < 90 g/L (in infants < 4 weeks: < 100 g/L)
  • Platelets < 100 x 10^9/L
  • Neutrophils < 1.0 x 10^9/L

Hypertriglyceridemia and/or hypofibrinogenemia:

  • Fasting triglycerides ≥ 3.0 mmol/L (≥ 265 mg/dL)
  • Fibrinogen ≤ 1.5 g/L

Hemophagocytosis: Hemophagocytosis in bone marrow, spleen, or lymph nodes without evidence of malignancy.

Low or absent NK cell activity: Documented by standard laboratory testing.

Ferritin: Serum ferritin ≥ 500 μg/L.

Elevated soluble CD25 (soluble IL-2 receptor): ≥ 2400 U/mL.

The patient met at least five of these eight criteria, confirming the diagnosis of HLH.

These findings, combined with the clinical presentation, met the diagnostic criteria for HLH.

Fig (1): Micrograph showing red blood cells within macrophages. H&E stain.

Management

Initially patient was treated with IV fluids, Empirical broad-spectrum antibiotics, and supportive medications, Over the next 24 hr patient had worsening symptoms with MODS. In view of the high index of suspicion of HLH, She was promptly started on pulse-dose corticosteroids (methylprednisolone) with other supportive measures, including high-flow oxygen. The treatment led to a significant clinical improvement within 48 hr, with normalization of laboratory parameters. She was shifted to the ward after the completion of pulse therapy and continued on supportive care. The patient continued to improve and was discharged after one week of care. She was scheduled for follow-up visits to monitor for potential relapse and manage any long-term complications.

Conclusion

Secondary HLH is a critical condition with an overall incidence of 1.2 cases per million persons per year. The prognosis is poor if unrecognized or untreated, with mortality rates exceeding 80%. Early diagnosis and appropriate treatment, such as corticosteroids, etoposide, and plasmapheresis, can significantly improve patient outcomes.

Dr. Harish Mallapura Maheshwarappa
Director – Institute of Critical Care Medicine

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