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, chro