Iron Deficiency Anemia
The most likely diagnosis is iron deficiency anemia (Option C). This 2-year-old presents with the classic triad of severe microcytic anemia (MCV 62 fL, Hb 4 g/dL), low ferritin (9 μg/L), and clear dietary risk factors—excessive cow's milk intake (3 glasses daily) with meat avoidance—which directly causes iron deficiency through both reduced iron intake and gastrointestinal microbleeding from cow's milk protein. 1, 2, 3
Why Iron Deficiency Anemia is the Clear Diagnosis
Laboratory findings are pathognomonic for iron deficiency:
- Ferritin 9 μg/L is definitively diagnostic, as serum ferritin <12 μg/dL confirms iron deficiency, and even in the presence of inflammation, ferritin <30 μg/L establishes the diagnosis. 1, 4
- Severe microcytosis (MCV 62 fL) with hypochromia (MCH 18 pg/cell) indicates impaired hemoglobin synthesis from iron depletion. 2, 5
- Elevated reticulocyte count (3%) reflects appropriate bone marrow response attempting to compensate for anemia, distinguishing this from bone marrow failure or chronic disease. 2
- Reactive thrombocytosis (480 × 10⁹/L) commonly accompanies severe iron deficiency in children. 3
Dietary history confirms the mechanism:
- Excessive cow's milk consumption (>24 ounces daily) is the most common cause of severe iron deficiency in toddlers, causing both reduced dietary iron intake and occult gastrointestinal blood loss from cow's milk protein-induced enteropathy. 3, 6
- Meat refusal eliminates the primary source of bioavailable heme iron. 3
- This dietary pattern is documented in nearly all children hospitalized with severe IDA. 6
Why Other Diagnoses Are Excluded
Sickle cell disease (Option A) is ruled out by:
- Normal reticulocyte response rather than the marked reticulocytosis (>10%) expected in chronic hemolysis. 2
- Absence of hemolytic features (no mention of jaundice, splenomegaly, or elevated indirect bilirubin). 2
- Low ferritin excludes hemolytic anemia, which typically shows normal or elevated ferritin from chronic transfusions or hemolysis. 1
Alpha thalassemia trait (Option B) is excluded by:
- Low ferritin definitively rules out thalassemia trait, as thalassemia presents with normal or elevated iron stores (ferritin typically >30 μg/L). 1, 7
- While thalassemia trait causes microcytosis, it produces mild anemia (Hb typically 10-12 g/dL) with elevated RBC count, not the severe anemia (Hb 4 g/dL) and low RBC count (3 × 10¹²/L) seen here. 7
- The family history of "similar presentation" likely reflects shared dietary patterns rather than genetic inheritance. 3, 6
Anemia of chronic disease (Option D) is excluded by:
- **Low ferritin (<30 μg/L) excludes ACD**, which requires ferritin >100 μg/L or 30-100 μg/L with transferrin saturation <20% in the presence of inflammation. 4, 1
- No clinical evidence of chronic inflammatory disease, infection, or malignancy. 4
- ACD causes functional iron sequestration with elevated ferritin, not true iron depletion. 1, 8
Critical Clinical Pitfalls to Avoid
Do not assume family history indicates genetic disease:
- Shared dietary patterns in siblings commonly cause similar presentations of nutritional iron deficiency, particularly in families with cultural preferences for high milk intake. 3, 6
- Many children with severe IDA have parents with private insurance and stable employment, indicating this is not solely a socioeconomic issue but a knowledge gap about appropriate toddler nutrition. 6
Do not overlook the severity requiring urgent intervention:
- Hemoglobin of 4 g/dL represents life-threatening anemia requiring immediate evaluation for transfusion and cardiac decompensation. 6
- This degree of anemia can cause irreversible neurodevelopmental and cognitive deficits in toddlers if not promptly corrected. 3
Do not perform unnecessary genetic testing: