Neonates
Microcytic
Three gene deletion α-thalassemia
Normocytic
Acute blood loss
Isoimmunization (antibody-mediated hemolysis) – ABO incompatibility; Rh incompatibility
Congenital hemolytic anemias (spherocytosis, glucose-6-phosphate dehydrogenase deficiency)
Congenital infections (including parvovirus B19)
Macrocytic
Congenital aplasia
Infants and toddlers
Microcytic
Iron deficiency anemia
Concurrent infection
Thalassemia
Normocytic
Concurrent infection
G6PD
Pyruvate kinase deficiency
Spherocytosis
Elliptocytosis
Autoimmune hemolytic anemia
Hypersplenism
Transient erythroblastopenia of childhood
Acute blood loss
Iron deficiency anemia
Acquired hemolytic anemia
Sickle cell disease
Leukemia
Myelofibrosis
Macrocytic
Vitamin B12 or folate deficiency
Hypothyroidism
Hypersplenism
Congenital aplasia
Older children and adolescents
Microcytic
Iron deficiency anemia
Anemia of chronic disease
Thalassemia
Normocytic
Acute blood loss
Iron deficiency anemia
Acquired hemolytic anemia
Sickle cell disease
Leukemia
Myelofibrosis
Anemia of chronic disease
Macrocytic
Vitamin B12 or folate deficiency
Hypothyroidism
Thinking about the differential
Iron deficiency anemia is usually microcytic.
Reference / Further Reading
Am Fam Physician. 2010 Jun 15;81(12):1462-1471. Evaluation of Anemia in Children. https://www.aafp.org/afp/2010/0615/p1462.html
Am Fam Physician. 2016 Feb 15;93(4):270-278. Iron Deficiency and Other Types of Anemia in Infants and Children. https://www.aafp.org/afp/2016/0215/p270.html