Anemia is defined as a decrease in the total amount of red blood cells (RBCs) or
hemoglobin in the blood and is present when it falls below certain
thresholds depending on the age, gender, and race of the patient.
Based on WHO criteria, the lower limit of normal in adults is 13 g/dL in
men and 12 g/dL in women. The blood hemoglobin concentration may more
accurately indicate the total red cell mass compared with the
hematocrit. The various types of anemia are due to blood loss
(usually gastrointestinal bleeding, trauma, others), decreased red
blood cell production (iron deficiency, a lack of vitamin B12, folic
acid, thalassemia, and a number of neoplasms), or increased red blood
cell breakdown ( genetic conditions such as sickle cell anemia,
infections e.g. malaria, and certain autoimmune diseases). The
type of anemia can also be classified based on the size of the red blood
cells and the amount of hemoglobin present in each cell.
Examples include: microcytic (smaller RBC's), macrocytic
(larger), or normocytic (normal RBC size). Hypochromic (paler than normal - less red).
Symptoms vary greatly and depend on the onset and the individual's
ability to compensate for a loss in oxygen-carrying capacity.
Anemia with a slow onset may go undetected or present with vague
symptoms including tiredness, weakness, shortness of breath, poor
concentration or reduced exercise tolerance. Anemia that occurs
rapidly often has more obvious symptoms such as confusion, mental status
changes, lightheadedness, loss of consciousness, palpitations,
respiratory distress, or hypotension. Symptoms are often more
severe if there is underlying coronary artery disease, congestive heart
failure, or intrinsic pulmonary or cerebrovascular disease.
Typical signs exhibited may include pallor (pale skin, lining mucosa,
conjunctiva and nail beds), however, further testing is required to
confirm the diagnosis.
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