Lead Poisoning is the Most Likely Diagnosis
The combination of normocytic, normochromic anemia with basophilic stippling, target cells, and shredded RBCs in a preschool-aged child is highly characteristic of lead poisoning (Answer C). 1
Key Diagnostic Features Supporting Lead Poisoning
The blood smear findings are pathognomonic for lead toxicity:
- Basophilic stippling represents aggregated ribosomes within red blood cells and is a classic finding in lead poisoning, though it can appear in other conditions 2, 3, 4
- Target cells and shredded RBCs indicate membrane damage from lead's toxic effects on erythrocyte structure 1
- Normocytic, normochromic pattern distinguishes this from iron deficiency, which would show microcytic, hypochromic cells 1
- Normal WBC count helps exclude other systemic processes or bone marrow disorders 1
Why Other Diagnoses Are Excluded
Iron Deficiency Anemia (Option A) - Incorrect
- Presents with microcytic, hypochromic red cells, not normocytic normochromic 1
- Shows low ferritin and transferrin saturation with elevated RDW 1
- Does not produce basophilic stippling 1
Hypothyroidism (Option B) - Incorrect
- Typically causes normocytic or macrocytic anemia, not the specific morphologic findings seen here 1
- Does not produce basophilic stippling or target cells 1
- Would be accompanied by other thyroid-related symptoms (growth delay, constipation, cold intolerance) 1
Anemia of Chronic Disease (Option D) - Incorrect
- Presents with normocytic anemia but with elevated ferritin >100 μg/L and transferrin saturation <20% 1
- Does not typically show basophilic stippling 1
- Would require evidence of underlying chronic inflammatory or infectious process 1
Clinical Context and Pitfalls
Preschool-aged children are at highest risk for lead poisoning due to hand-to-mouth behavior and exposure to lead-based paint in older housing 3, 5. The presentation with pallor and anemia may be the initial manifestation before other systemic symptoms develop 3.
Important Diagnostic Considerations:
- Basophilic stippling may be absent in peripheral blood even when present in bone marrow, so its absence does not exclude lead poisoning 2
- Basophilic stippling is nonspecific and can occur in other conditions, but the constellation of findings here (normocytic anemia + stippling + target cells + shredded RBCs) strongly points to lead toxicity 4
- Confirm diagnosis with blood lead level measurement and zinc protoporphyrin levels 3, 6
Next Steps After Diagnosis:
- Obtain blood lead level (diagnostic if elevated) 3, 6
- Measure zinc protoporphyrin (elevated in lead poisoning) 3, 5
- Assess for decreased erythrocyte ALA-dehydratase activity 3
- Investigate environmental sources (paint chips, contaminated soil, imported products) 3, 5, 6
- Consider chelation therapy with EDTA or succimer depending on blood lead levels 3