What is the cause of significantly elevated ferritin and LDH levels in an adult patient with a grossly normal CBC?

Extreme Hyperferritinemia with Elevated LDH and Normal CBC

In an adult patient with ferritin >7500 μg/L, LDH 1113, and normal CBC, the most likely diagnoses are hemophagocytic lymphohistiocytosis (HLH), hematologic malignancy (particularly lymphoma or acute leukemia), or severe systemic infection—not iron overload. Ferritin levels >7500 μg/L rarely represent simple iron overload and demand urgent evaluation for life-threatening conditions 1.

Critical First Steps

Immediately assess for hemophagocytic lymphohistiocytosis (HLH) using the HLH-2004 diagnostic criteria, as this is a potentially fatal syndrome that requires urgent recognition 2:

• Fever pattern: Persistent or recurrent fever 3
• Splenomegaly: Physical examination finding 3
• Cytopenias: While your CBC is "grossly normal," carefully review for subtle decreases in ≥2 cell lines (hemoglobin <9 g/dL, platelets <100,000/μL, neutrophils <1000/μL) 3
• Hypertriglyceridemia: Fasting triglycerides ≥265 mg/dL or fibrinogen ≤150 mg/dL 3
• Hemophagocytosis: Bone marrow, spleen, or lymph node biopsy showing hemophagocytosis 3
• Low/absent NK cell activity: If available 3
• Soluble IL-2 receptor (sCD25): Elevated if available 3

The combination of extreme hyperferritinemia (>7500 μg/L) with elevated LDH strongly suggests HLH, particularly if ferritin continues rising 3, 4.

Differential Diagnosis by Ferritin Level

Ferritin >7500 μg/L: High-Risk Conditions

Hematologic malignancy is the most common cause of extreme hyperferritinemia in adults (25.7% of cases with ferritin >10,000 μg/L) 4:

• T/NK cell lymphoma: Strongly associated with extreme ferritin elevation 2
• Acute myeloblastic leukemia: Positively associated with maximum ferritin 2
• Other lymphomas: Common cause of marked hyperferritinemia 5, 6

Severe infection is a leading cause, particularly in the setting of sepsis or septic shock 6, 2:

• Non-HIV infections are the most frequent cause of hyperferritinemia overall 6
• Sepsis and septic shock show positive associations with maximum ferritin in multivariable analysis 2
• The elevated LDH supports tissue injury from severe infection 3

Liver disease (except hepatitis) is positively associated with extreme ferritin elevation 2:

• Acute or subacute liver failure shows strong positive association with maximum ferritin 2
• Hepatic veno-occlusive disease is associated with extreme hyperferritinemia 2
• Check AST, ALT, bilirubin, albumin, and INR immediately 1

Adult-onset Still's disease (AOSD) causes extreme hyperferritinemia (4,000-30,000 ng/mL, occasionally up to 250,000 ng/mL) 1:

• Look for persistent fever, salmon-pink rash, arthritis/arthralgias 1
• Glycosylated ferritin fraction <20% is 93% specific for AOSD when combined with 5-fold ferritin elevation 1
• Serum ferritin correlates with disease activity 1

Essential Diagnostic Workup

Immediate Laboratory Tests

Complete metabolic panel with liver function tests 1:

• AST, ALT, alkaline phosphatase, bilirubin, albumin
• Acute hepatitis and hepatocellular necrosis release ferritin from damaged hepatocytes 1

Inflammatory markers 1:

• CRP and ESR to quantify systemic inflammation
• Elevated inflammatory markers with extreme ferritin suggest secondary hyperferritinemia 1

Transferrin saturation (TS) 1:

• If TS <45%, iron overload is excluded and secondary causes predominate 1
• In inflammatory states, ferritin rises acutely while TS often drops 1
• This pattern (high ferritin, low TS) confirms inflammatory hyperferritinemia, not iron overload 1

Additional critical tests:

• Triglycerides and fibrinogen (for HLH criteria) 3
• Peripheral blood smear to identify microangiopathic changes or abnormal cells 3
• Creatine kinase (CK) to evaluate for muscle necrosis 1
• Procalcitonin if bacterial infection suspected 3
• Soluble IL-2 receptor (sCD25) if available for HLH evaluation 3

Imaging and Tissue Diagnosis

CT chest/abdomen/pelvis with contrast to evaluate for:

• Lymphadenopathy suggesting lymphoma 1
• Splenomegaly (HLH criterion) 3
• Hepatomegaly or liver pathology 2
• Occult malignancy 5, 6

Bone marrow biopsy is essential if hematologic malignancy or HLH suspected 3, 4:

• Evaluate for hemophagocytosis (HLH criterion) 3
• Assess for acute leukemia, lymphoma, or other hematologic malignancy 4, 2
• Even with "grossly normal" CBC, bone marrow may reveal underlying pathology 4

Glycosylated ferritin fraction if AOSD suspected (ferritin continues rising or exceeds 4,000-5,000 ng/mL with persistent fever) 1:

• <20% is 93% specific for AOSD 1

Critical Pitfalls to Avoid

Do not assume iron overload with ferritin >7500 μg/L 1, 7:

• Extremely high ferritin (>10,000 μg/L) rarely represents simple iron overload 1
• Check transferrin saturation—if <45%, iron overload is excluded 1
• Only 14.2% of adults with ferritin >10,000 μg/L have HLH, but common causes (malignancy, infection, liver disease) must be excluded first 4

Do not delay evaluation for life-threatening conditions 1, 4:

• Ferritin >7500 μg/L with elevated LDH indicates high risk of HLH, malignancy, or severe infection 3, 4, 2
• HLH is potentially fatal and requires urgent recognition and treatment 2
• Hematologic malignancies require prompt diagnosis for treatment planning 5, 4

Do not overlook multiple concurrent etiologies 6:

• 70% of patients with marked hyperferritinemia (>10,000 μg/L) have multiple underlying causes 6
• 41% of patients with ferritin >500 μg/L have multiple causes 6
• The more underlying causes present, the higher the ferritin level tends to be 6

Do not miss subtle cytopenias 3:

• "Grossly normal" CBC may still show early or mild decreases in cell lines
• Carefully review absolute values against HLH criteria thresholds
• Serial CBCs may reveal evolving cytopenias 3

Algorithmic Approach

1. Urgent HLH evaluation: Apply HLH-2004 criteria immediately 3, 2
2. Check transferrin saturation: If <45%, exclude iron overload and focus on secondary causes 1
3. Assess for malignancy: Order CT imaging and consider bone marrow biopsy 5, 4, 2
4. Evaluate for severe infection: Blood cultures, procalcitonin, assess for sepsis/septic shock 6, 2
5. Screen for liver disease: Comprehensive hepatic panel, consider hepatology consultation if abnormal 2
6. Consider AOSD: If persistent fever with ferritin >4,000 ng/mL, check glycosylated ferritin fraction 1
7. Multidisciplinary consultation: Involve hematology urgently given extreme ferritin elevation and elevated LDH 4, 2