Definition
- Anemia is a laboratory finding reflecting a decrease in red blood cell (RBC) mass below an age-appropriate normative value; this can be either:
- Reduction in RBC number
- Reduction in RBC mass (hematocrit)
- Reduced hemoglobin concentration
- Anemia may be associated with pallor but is more likely to be a silent symptom.
- Pallor and anemia are clinical manifestations of an underlying disease process requiring a thorough evaluation.
- Types of anemia
- Microcytic anemias: mean corpuscular volume (MCV) less than appropriate for age
- Normocytic anemias: MCV within normal range for age
- Macrocytic anemias: MCV greater than appropriate for age
- MCV changes with age; see Laboratory Evaluation for normal values.
Epidemiology
- Age
- Race/ethnicity
- Black persons are at greatest risk for sickle cell anemia.
- Thalassemias occur primarily in patients of Mediterranean and Southeast Asian descent.
Mechanism
- Sideroblastic anemia is inherited and occurs in childhood.
-
Iron-deficiency anemia results from:
- Poor iron intake
- Poor iron absorption
- Blood loss
- Common causes of gastrointestinal bleeding
- Cow milk protein allergy
- Gastric and duodenal ulcers
- Meckel diverticulum
- Polyps
- Hemorrhoids
- Gastritis
- Thalassemias are disorders of hemoglobin production.
- α-Thalassemia is caused by deficient production of the α chain.
- β-Thalassemia is caused by deficient production of the β chain.
- Causes of microcytic anemia
-
Iron-deficiency anemia
- Lead poisoning
- Copper deficiency
- Malnutrition
- Chronic disease
- Thalassemia
- Hemoglobin E trait
- Sideroblastic anemia
- Atransferrinemia
- Inborn errors of metabolism
- Causes of normocytic anemia
- Infection
- Acute blood loss
- Renal disease
- Connective tissue disorder
- Hepatic disease
- Hemolysis
- Hypersplenism
- Cancer
- Aplastic anemia
- Dyserythropoietic anemia
- Drugs
- Causes of macrocytic anemia
- Megaloblastic anemias from vitamin B12 or folate deficiency
- Reticulocytosis
- Postsplenectomy
- Myelodysplastic syndrome
- Aplastic anemia
- Fanconi anemia
- Diamond-Blackfan anemia
- Persons syndrome
- Dyskeratosis congenita
- Paroxysmal nocturnal hemoglobinuria
-
Down syndrome
-
Hypothyroidism
- Hepatic disease, jaundice
- Drugs (eg, phenytoin, methotrexate)
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