Anemias

2021-02-24 12:00 AM

Anaemia is a reduction below normal limits of the total circulating red cell mass.

ANEMIAS

Anemia is a reduction below normal limits of the total circulating red cell mass. Signsof anemia include palpitations, dizziness, angina, pallor of skin and nails, weakness, claudication, fatigue, and lethargy.

  • Reticulocytes are immature, larger red cells (macrocytic cells) that are spherical and have a bluish color (polychromasia) due to free ribosomal RNA. Reticulocytes do not have a nucleus; note that any erythrocyte with a nucleus (nRBC) in peripheral blood is abnormal. Reticulocyte maturation to a mature erythrocyte takes about 1 day. The reticulocyte count is the percentage of red immature cells present in peripheral blood (normal 0.5–1.5%).

The corrected reticulocyte count takes into consideration the degree of anemia and is calculated as (patient’s hct/45) × (reticulocyte count); the idea behind the calculation is to scale the reticulocyte count by multiplying by the ratio of the patient’s hematocrit to “normal” hematocrit of 45%. When interpreting the corrected reticulocyte count, <2% indicates poor bone marrow response and >3% indicates good bone marrow response.

  • The reticulocyte production index is the corrected reticulocyte count/2; use this measure if bone marrow reticulocytes (shift cells) are present (polychromasia). The division by 2 is because shift cells take twice as long as reticulo-cytes to mature (2 days versus 1 day).

Classification of anemia can be based on color: normochromic anaemias have normal red cell color (central pallor of about a third the diameter of the erythrocyte); hypochromic anemias have decreased color (seen as an increased central pallor of erythrocyte); and hyperchromic anemias, while theoretically possible, are usually instead called spherocytosis and have increased color (loss of central pallor of erythrocyte). Classification of anemia can also be based on size (MCV).

The pathogenesis of anaemia varies with the underlying disease. Blood loss can cause anaemia. Hemolytic anaemias are also important and include hereditary spherocytosis, glucose-6-phosphate dehydrogenase deficiency, sickle cell disease, haemoglobin C disease, thalassemia, and paroxysmal nocturnal hemoglobinuria. Immuno-molytic anaemias, which are hemolytic anaemias with an immune component to the pathology, include autoimmune hemolytic anaemia (AIHA), cold AIHA, incompatible blood transfusions, and hemolytic disease of the newborn. Anaemias of diminished erythropoiesis include megaloblastic anaemia (B12 and folate deficiencies), iron deficiency anaemia, anaemia of chronic disease, aplastic anaemia, myelophthisic anaemia, and sideroblastic anaemia.