Hemophagocytic Lymphohistiocytosis

Aka: Hemophagocytic Lymphohistiocytosis

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II. Epidemiology

  1. Rare

III. Pathophysiology

  1. Impaired Natural Killer Cell activity triggers over-activation of Macrophages and cytotoxic T Cells (CD8 T Cells)
  2. Immune System overactivation with histiocyte, T-Cell and Macrophage accumulation in the skin, liver and Spleen
  3. Results in Phagocytosis of Red Blood Cells, White Blood Cells and Platelets
  4. Also results in increased Cytokine release with a severe inflammatory response

IV. Causes

  1. Primary (Hereditary)
    1. Diagnosed in infancy
  2. Secondary (Significant physiologic stressors)
    1. Infection
    2. Immunodeficiency
    3. Autoimmune Conditions
    4. Malignancy

V. Differential Diagnosis

  1. Sepsis
  2. Acute Hepatic Failure
  3. Disseminated Intravascular Coagulation
  4. Influenza-like illness (e.g. Covid19)
  5. Toxin Ingestion
  6. Antiphospholipid Syndrome
  7. Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS Syndrome)

VI. Findings

  1. Fever (>90%)
  2. Splenomegaly (>80%)
  3. Hepatomegaly (>60%)
  4. Respiratory dysfunction (>30%)
  5. CNS dysfunction (>30%)

VII. Labs

  1. Labs should also address differential diagnosis (e.g. Sepsis)
  2. Complete Blood Count
    1. Pancytopenia
  3. Comprehensive Metabolic Panel
    1. Abnormal Liver Function Tests
    2. Hypoalbuminemia
  4. Serum Ferritin
    1. Levels are frequently >2000 mcg/L
  5. Coagulation Studies (e.g. PTT, INR)
    1. Coagulopathy
    2. Fibrinogen decreased
    3. D-Dimer increased
  6. Other Studies
    1. Serum Triglycerides increased

VIII. Management

  1. Patients typically present with toxic appearance
    1. ABC Management
    2. Fluid Resuscitation
    3. Antibiotics are typically started (due to risk of underlying infectious cause)
  2. Consult Hematology and Intensive Care Medicine
    1. Discuss evaluation and management
    2. Antiiflammatory agents are typically used
      1. Corticosteroids
      2. Biologic Agents (e.g. Anakinra, Ruxolitinib, Etoposide)

IX. Prognosis

  1. Mortality 20 to 80% (increased with delayed diagnosis)

X. Resources

  1. Konkol S, Rai M (2022) Lymphohistiocytosis, StatPearls, Treasure Island, FL,
    1. https://www.ncbi.nlm.nih.gov/books/NBK557776/

XI. References

  1. Long and Lentz in Swadron (2022) EM: Rap 22(8): 11-2

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