Chronic anemia has no precise definition. Anemia that persists for 6 months or more (eg, hereditary spherocytosis [HS]) is clearly chronic; however, anemia that lasts only 2 months (eg, iron deficiency that is being treated) should also be considered chronic anemia, and other explanations must be sought.
Chronic anemia can be primary or secondary.
Primary chronic anemia
Primary chronic anemias are the true chronic anemias, in which anemia (defined as a hemoglobin level more than 2 standard deviations below the mean reference value for age) is part of the basic disease process. The basic disease process is hematologic (eg, sickle cell disease, HS), and the degree of anemia varies markedly from etiology to etiology and from patient to patient, even with the same etiology. (See Etiology and Workup.)
Secondary chronic anemia
Secondary chronic anemias are chronic anemias that may provide a diagnostic clue to an underlying pathology. They are the consequence of a nonhematologic problem (eg, chronic blood loss, chronic renal failure, osteomyelitis, inflammatory bowel disease, tuberculosis).
Chronic anemia is classified into the following 3 primary categories:
Decreased red cell production
Increased red cell destruction (hemolysis)
Patients with chronic anemia are usually asymptomatic, even with remarkably low levels of hemoglobin. Symptoms more often relate to the underlying cause.
Hemoglobin levels as low as 5-6 g/dL are well tolerated in most patients, and patients do not require transfusion. Parents, however, frequently note that patients become much more active following a transfusion.
Inquire carefully regarding any evidence of blood loss (eg, hemoptysis, hematochezia, melina, hematuria, menorrhagia). In endemic areas, a history of papulovesicular skin lesions on the feet may suggest a diagnosis of hookworm infestation.
Age is always an important consideration. Nutritional iron deficiency is seen in older infants and toddlers (aged 6 mo to 3 y), whereas iron deficiency due to blood loss occurs in menstruating girls. The deficiency can be surprisingly severe, but transfusion is indicated only in the rare circumstance of impending high-output cardiac failure.
The patient’s sex must always be considered in hemolytic anemias. Severe G-6-PD deficiency may be seen as a chronic nonspherocytic anemia, usually in males.
Dietary history is important with regard to the amount and source of milk ingested by infants and toddlers and to their risk of chronic iron deficiency (24 oz of milk/d or more is a clear risk factor for nutritional iron deficiency in infants and young children).