What is the recommended workup, management, and treatment for hemophagocytic lymphohistiocytosis (HLH)?

HLH Workup, Management, and Treatment

Diagnose HLH using the HLH-2004 criteria (5 of 8 criteria) combined with clinical judgment, immediately initiate a meticulous search for underlying triggers (infections, malignancies, autoimmune disease), and start immunosuppressive therapy promptly with corticosteroids as the cornerstone, escalating to etoposide-based regimens for severe or refractory disease. 1

Diagnostic Workup

HLH-2004 Diagnostic Criteria (Need 5 of 8)

The diagnosis requires meeting 5 of the following 8 criteria 1:

• Fever
• Splenomegaly
• Cytopenias (≥2 lineages):
  • Hemoglobin <90 g/L
  • Platelets <100 × 10⁹/L
  • Neutrophils <1.0 × 10⁹/L
• Hypertriglyceridemia and/or hypofibrinogenemia:
  • Fasting triglycerides ≥3.0 mmol/L (≥265 mg/dL)
  • Fibrinogen ≤1.5 g/L
• Hemophagocytosis in bone marrow, spleen, or lymph nodes (no malignancy evidence)
• Low/absent NK cell activity
• Ferritin ≥500 μg/L (levels >7,000-10,000 μg/L are highly suggestive in adults)
• Soluble CD25 (IL-2 receptor) ≥2,400 U/mL

Critical caveat: Hyperferritinemia >10,000 μg/L is >90% sensitive and specific in children but less specific in adults—integrate multiple clinical features. HLH-directed therapy may be initiated even if 5 criteria are not yet fulfilled when clinical suspicion is high. 1

Essential Trigger Investigation

Continue searching for triggers despite ongoing HLH treatment 1:

Infection Workup

• Viral: EBV (most common), CMV, HIV, influenza
• EBV DNA levels >10³ copies/mL are relevant for EBV-HLH development 1
• Comprehensive infectious disease panel including bacterial, fungal, parasitic causes

Malignancy Workup (40-70% of adult HLH cases)

Lymphomas are the predominant malignancy trigger 1:

• T-cell/NK-cell lymphomas (35%)
• B-cell lymphomas (32%)
• High-risk subtypes: Hodgkin, angioimmunoblastic T-cell, anaplastic large cell, NK/T-cell, intravascular B-cell lymphoma

Aggressive malignancy search 1:

• PET-guided imaging
• Repetitive tissue sampling if initial biopsies negative
• Lymphoma reference pathologist consultation
• Consider splenectomy in HLH of unknown cause with splenomegaly to detect occult lymphomas
• Elevated sCD25/ferritin ratio suggests lymphoma-associated HLH

Autoimmune/Autoinflammatory Disorders

• Macrophage activation syndrome (MAS-HLH): Still's disease, lupus, vasculitis
• Treatment differs from other secondary HLH forms 1

Genetic Testing

Consider in 1:

• Family history of consanguinity/HLH
• Partial albinism
• Recurrent disease
• Young males with EBV infection/lymphoproliferation
• Unknown trigger

Do not delay treatment pending genetic results 1

Treatment Algorithm

Initial Management: All Patients

Start corticosteroids immediately 1, 2:

• Prednisolone 1-2 mg/kg/day OR
• Dexamethasone 5-10 mg/m²/day

Supportive care:

• Aggressive ICU-level support for multiorgan failure 2
• Broad antimicrobial prophylaxis: Pneumocystis jirovecii, fungi, consider antiviral prophylaxis due to severe T-cell depletion 1
• HEPA-filtered air hospitalization 1

Treatment Escalation Based on Clinical Scenario

Infection-Associated HLH (Especially EBV-HLH)

Mild-to-moderate disease with improving manifestations:

• Short course corticosteroids ± IVIG (1.6 g/kg over 2-3 days) 1
• Monitor ferritin, sCD25, cell counts, EBV DNA

Severe disease or rapid deterioration:

• Add etoposide immediately (HLH-94 protocol) 1
• Add rituximab for EBV-HLH: 375 mg/m² weekly × 2-4 doses to clear B-cell viral reservoir 1

Malignancy-Triggered HLH

Distinguish from "HLH During Chemotherapy" (infection-triggered during immunosuppression) 3:

Malignancy-triggered HLH at presentation/relapse:

• Initiate lymphoma-directed therapy early when feasible 4
• Add etoposide for high-risk patients (HLH-94 protocol)
• Corticosteroids + IVIG
• Consider non-myelosuppressive regimens in critically ill: anakinra, ruxolitinib, IVIG 4

HLH During Chemotherapy (infection-triggered):

• Corticosteroids (prednisolone 1-2 mg/kg or dexamethasone 5-10 mg/m²) + IVIG 1
• Use etoposide sparingly—bone marrow recovery essential for immune reconstitution 1
• Aggressive antimicrobial therapy
• Monitor for recurrent malignancy as alternate trigger

MAS-HLH (Autoimmune/Autoinflammatory)

First-line: High-dose corticosteroids 1, 2

Insufficient response:

• IL-1 inhibition (anakinra) and/or
• Cyclosporine A 2

Severe, persistent, or relapsing MAS:

• Add individualized, age-adjusted etoposide 2

Standard HLH-94 Protocol Components

For severe/refractory disease requiring full protocol 1:

• Etoposide (typically 8 weeks; weekly reevaluation for continued need)
• Dexamethasone
• Cyclosporine A (may substitute tacrolimus with careful drug level monitoring)
• IVIG (blocks complement, Fc receptors, neutralizes cytokines—though questioned in adult Still's disease) 1

Maintenance therapy: Consider for residual disease after 8 weeks or patients requiring allogeneic stem cell transplant 1

Novel/Emerging Therapies

For refractory disease 5, 2:

• Emapalumab (IFN-γ blockade)
• Alemtuzumab
• Anakinra (IL-1 inhibition)
• Ruxolitinib (JAK inhibitor)
• Tocilizumab (IL-6 inhibition)

Critical Pitfalls to Avoid

1. Delaying treatment while awaiting 5/8 criteria—initiate therapy on strong clinical suspicion 1

2. Stopping trigger search after HLH treatment begins—continue meticulous investigation throughout treatment 1

3. Missing occult lymphomas—requires aggressive, repetitive tissue sampling and PET imaging 1

4. Inadequate infection prophylaxis—severe T-cell depletion mandates broad antimicrobial coverage 1

5. Overusing etoposide in "HLH During Chemotherapy"—prioritize bone marrow recovery for immune reconstitution 1

6. Treating MAS-HLH like other secondary HLH—requires IL-1 inhibition/cyclosporine rather than immediate etoposide 1, 2

7. Ignoring EBV as co-trigger in lymphoma-associated HLH—consider rituximab when EBV present 1

Monitoring and Reassessment

• Weekly reevaluation of need for continued etoposide therapy 1
• Serial monitoring: ferritin, sCD25, cell counts, trigger-specific markers (e.g., EBV DNA)
• Serial bone marrow aspirates if hemophagocytosis not initially demonstrated 1
• Ongoing surveillance for secondary infections during immunosuppression 1

Prognosis: Adult HLH mortality ranges 20-88%, primarily from refractory HLH, secondary infections, and progression of underlying trigger 1. Early aggressive treatment and trigger identification are essential for survival.