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- Matthew Richardson, MD*
- *Section of Pediatric Hematology/Oncology, Baystate Children’s Hospital, Springfield, Mass
Objectives
After completing this article, readers should be able to:
Discuss the common causes of microcytic anemia in children.
Define the most common cause of microcytic anemia in children.
Distinguish iron deficiency anemia from beta thalassemia trait.
Recognize when disorders of beta-globin may present in infants.
Microcytic Anemia
Anemia is the most common hematologic abnormality that pediatricians encounter. The differential diagnosis for anemia in children includes congenital, acquired, benign, malignant, common, and extraordinarily rare disorders. Thankfully, most conditions cause consistent changes in the mean cell volume (MCV) of red blood cells (RBCs) and can be grouped by using this parameter. In children, anemia is caused most often by disorders that result in smaller-than-normal RBCs (microcytosis) (Table 1). With a thorough history, a good physical examination, and perhaps some additional blood work, the correct cause of a child’s microcytic anemia can be discovered.
| Common |
|
| Less Common |
|
Causes of Microcytic Anemia
Is It Anemia? Is It Microcytic?
Automated blood counters may not take into account the normal variations in hemoglobin/hematocrit and MCV that are seen throughout childhood. Results reported as abnormal must be compared with age-specific values (Table 2). Values that are 2 standard deviations below the age-appropriate mean can be considered abnormal.
| Age | Mean Hemogobin (g/dL) (g/L) | “−2SD” | Mean Hematocrit (%) (Proportion of 1.0) | “−2SD” | Mean Cell Volume (mcm3) | “−2SD” |
|---|---|---|---|---|---|---|
| Birth | 16.5 (165) | 13.5 (135) | 51 (0.51) | 42 (0.42) | 108 | 98 |
| 1 to 3 d | 18.5 (185) | 14.5 (145) | 56 (0.56) | 45 (0.45) | 108 | 95 |
| 1 mo | 14.0 (140) | 10.0 (100) | 43 (0.43) | 31 (0.31) | 104 | 85 |
| 2 mo | 11.5 (115) | 9.0 (90) | 35 (0.35) | 28 (0.28) | 96 | 77 |
| 3 to 6 mo | 11.5 (115) | 9.5 (95) | 35 (0.35) | 29 (0.29) | 91 | 74 |
| 6 mo to 2 y | 12.0 (120) | 10.5 (105) | 36 (0.36) | 33 (0.33) | 78 | 70 |
| 2 to 6 y | 12.5 (125) | 11.5 (115) | 37 (0.37) | 34 (0.34) | 81 | 75 |
| 6 to 12 y | 13.5 (135) | 11.5 (115) | 40 (0.40) | 35 (0.35) | 86 | 77 |
| 12 to 18 y | ||||||
| Female | 14.0 (140) | 12.0 (120) | 41 (0.41) | 36 (0.36) | 90 | 78 |
| Male | 14.5 (145) | 13.0 (130) | 43 (0.43) | 37 (0.37) | 88 | 78 |
| 18 to 49 y | ||||||
| Female | 14.0 (140) | 12.0 (120) | 41 (0.41) | 36 (0.36) | 90 | 80 |
| Male | 15.5 (155) | 13.5 (135) | 47 (0.47) | 41 (0.41) | 90 | 80 |
↵* Adapted from Nathan DG, Orkin SH, Look AT, Ginsburg D, eds. Nathan and Oski’s Hematology of Infancy and Childhood. 6th ed. Philadelphia, Pa: Saunders; 2003, with permission from Elsevier.
Hemoglobin and Mean Cell Volume Throughout Childhood*
Hemoglobin Overview
Because disorders of heme metabolism or globin synthesis can lead to microcytic anemia, an appreciation of hemoglobin structure and how it changes over the first few months after birth is important. Hemoglobin is produced by a multistep process involving several enzymes in mitochondria and the cytosol. Hemoglobin consists of an iron-containing heme …
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