Diagnosis: Acute Hemolytic Anemia with Hyperbilirubinemia
This 6-year-old boy most likely has acute hemolytic anemia, evidenced by the combination of normocytic normochromic anemia (Hb 9.0 g/dL), elevated indirect bilirubin (0.82 mg/dL), presence of normoblasts, and atypical lymphocytes suggesting a reactive process. 1, 2
Key Diagnostic Features Supporting Hemolysis
The laboratory constellation strongly indicates active red blood cell destruction:
Normocytic normochromic anemia (Hb 9.0 g/dL) is characteristic of hemolytic processes, as hemolysis typically presents with normocytic or macrocytic indices rather than microcytic 2, 3
Elevated indirect (unconjugated) bilirubin (0.82 mg/dL) reflects increased red cell destruction with release of unconjugated bilirubin, a hallmark of hemolysis 4, 1, 2
Presence of normoblasts in peripheral blood indicates bone marrow stress response attempting to compensate for accelerated red cell destruction 2
Atypical lymphocytes suggest a reactive immune response, commonly seen in viral-triggered hemolytic processes 2, 5
Most Likely Etiologies in This Age Group
Infection-Triggered Hemolysis (Primary Consideration)
Viral infections are the most common trigger for acute hemolytic anemia in children, particularly with atypical lymphocytes present. 2, 5
- Epstein-Barr virus, cytomegalovirus, and other viral pathogens can trigger autoimmune hemolytic anemia in pediatric patients 5
- The atypical lymphocytes strongly support a viral etiology 2
Autoimmune Hemolytic Anemia (AIHA)
Secondary AIHA should be strongly considered given:
- The acute presentation with hemolysis markers 5
- Atypical lymphocytes suggesting immune activation 5
- Age-appropriate presentation for post-infectious AIHA 2, 5
Critical Next Steps for Diagnosis
Immediate laboratory evaluation must include:
Direct antiglobulin test (Coombs test) to differentiate immune from non-immune hemolysis - this is the single most important next test 1, 2, 5
Reticulocyte count to confirm bone marrow response (should be elevated in hemolysis) 1, 2, 3
Lactate dehydrogenase (LDH) - expected to be markedly elevated in hemolysis 4, 1, 2
Haptoglobin level - should be decreased or undetectable in active hemolysis 1, 2, 3
Peripheral blood smear review for schistocytes (suggesting microangiopathic process) or spherocytes (suggesting immune-mediated hemolysis) 1, 2
Important Differential Considerations
Exclude Thrombotic Microangiopathy
- Check platelet count carefully - the question states "normal" but TTP/HUS would show thrombocytopenia 4, 1
- If platelets are truly normal, TTP is unlikely 4
- Consider stool examination for verotoxin-producing E. coli if diarrhea is present 1
Hereditary Hemolytic Disorders
Less likely given acute presentation, but consider:
- G6PD deficiency (can be triggered by infections or medications) 2
- Hereditary spherocytosis (though typically presents earlier) 1, 2
Clinical Pitfalls to Avoid
Do not mistake this for anemia of chronic disease - the elevated indirect bilirubin and normoblasts indicate active hemolysis, not chronic inflammatory anemia 6
Do not delay direct Coombs testing - this single test determines whether immunosuppressive therapy (corticosteroids) is indicated 5
Do not assume iron deficiency - normocytic indices and hemolysis markers exclude this diagnosis 7, 6
Management Approach Based on Coombs Result
If Direct Coombs Positive (Warm AIHA)
- Initiate corticosteroids immediately (prednisone 1-2 mg/kg/day) as first-line therapy 5
- Consider high-dose immunoglobulins in severe cases 5
- Monitor hemoglobin closely for response 5
If Direct Coombs Negative
- Investigate non-immune causes: hereditary disorders, oxidative damage, mechanical hemolysis 2
- Review medication history for drug-induced hemolysis 1, 2
- Consider G6PD enzyme assay if appropriate ethnic background or triggering exposure 2
The normal leukocyte count and normal NLR (1.71) argue against severe systemic infection or malignancy, making post-viral AIHA the most probable diagnosis. 5