📊 Classification by MCV
• Microcytic (MCV <80): iron deficiency (most common), thalassemia, lead poisoning, anemia of chronic disease
• Normocytic (MCV 80-100): acute blood loss, hemolysis, bone marrow failure, anemia of chronic disease
• Macrocytic (MCV >100): B12/folate deficiency, Diamond-Blackfan, liver disease, hypothyroidism
🩸 Iron Deficiency (Most Common)
• Risk factors: excessive cow's milk (>24 oz/day), low-iron formula, poor diet, prematurity, menstrual blood loss
• Labs: low MCV, high RDW, low ferritin, low serum iron, high TIBC
• Treatment: elemental iron 3-6 mg/kg/day; response (Hb rise 1 g/dL in 2-4 weeks)
🩺 Hemolytic Anemia
• Labs: elevated reticulocyte count, elevated indirect bilirubin, elevated LDH, low haptoglobin, abnormal smear
• Sickle cell: HbS, increased risk of aplastic crisis (parvovirus B19)
• G6PD deficiency: X-linked, oxidative triggers (fava beans, sulfa drugs), bite cells, Heinz bodies
• Hereditary spherocytosis: autosomal dominant, spherocytes, increased osmotic fragility
⚠️ Red Flags
• Pancytopenia → bone marrow failure (Fanconi anemia, aplastic anemia, leukemia)
• Pallor + bruising/bleeding + fever → leukemia
• Jaundice + dark urine + splenomegaly → hemolysis
• Failure to thrive + chronic anemia → consider thalassemia major, Diamond-Blackfan
📌 Decision strategy: MCV guides initial differential. Microcytic + high RDW → iron deficiency. Microcytic + normal RDW → thalassemia trait. Elevated reticulocytes → hemolysis or blood loss.