Special Studies Of Red Blood Cell (RBC)

RBC (Red blood cells)

Normal, mature red blood cells are uniform in size (7 µm) and do not have a nucleus as do most other cells. They are round and flattened like a doughnut with a depression in the middle instead of a hole (biconcave). With routine staining, due to the haemoglobin inside the RBCs, they appear pink to red in colour with a pale centre. While not every RBC will be perfect, the presence of many cells that are different in shape or size may indicate a more severe problem. There may be one or more irregularities present and may include:

• Anisocytosis - variable sizes of red cells. The presence of smaller RBCs (<7 µm) is referred to as microcytosis and RBCs larger than 7 µm is macrocytosis.
  
  
  
• Poikilocytosis - various shapes of red cells. These may include echinocytes, acanthocytes, elliptocytes, keratocytes, sickle cells, target cells, teardrop cells (dacrocytes), smear cells (also known as smudge or basket cells), and schistocytes. 
   

  
  

  
  

  
  

  
  

  
  

  Red blood cell irregularities:

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  Size

  ·  Anisocytosis: this is abnormal variation in size of RBCs

  ·  Macrocytosis: large RBCs that may be due to a vitamin B12 or folate deficiency (megaloblastic anaemia). They are seen in pernicious anaemia, liver disease, in patients with underactive thyroid glands, in some bone marrow diseases, and sometimes in pregnancy.

  ·  Microcytosis: this is the presence of small RBCs that may be due to iron deficiency anaemia, long-standing inflammation due to infections or conditions such as rheumatoid arthritis, or to an inherited disorder such as thalassaemia.

  Shape - Poikilocytosis is a variation in the shape of an RBC and may include several different abnormalities at the same time.

  ·  Acanthocytes (spur, thorn or spiculated cells): irregular shaped cells with 5-10 spicules. May be present with liver or thyroid conditions, or in post-splenectomy patients.

  ·  Echinocytes (burr, crenated or berry cells): may have 10-30 spiny projections and often seen in patients with renal failure or malnutrition May be an artefact - something caused during sample preparation.

  ·  Elliptocytes elliptical-shaped RBC seen in hereditary elliptocytosis and various anaemias.

  ·  Keratocyte (horn cell): A half-moon or spindle shaped RBC that may be seen in patients with disseminated intravascular coagulation (DIC) or a vascular prosthesis.

  ·  Rouleaux: RBCs that appear as a stack of coins and seen in patients with inflammatory illnesses, anaemia, multiple myeloma or macroglobulinaemia.

  ·  Sickle cells: crescent-shaped RBCs characteristic of sickle cell anaemia.

  ·  Target cells (leptocytes or codocytes): RBCs that resemble a bull's-eye. Commonly seen in patients with liver disease, iron deficiency, haemoglobinopathies (abnormal inherited forms of haemoglobin), thalassaemia.

  ·  Teardrop cells (dacrocytes): RBCs that resemble a teardrop. Often seen in patients with myelofibrosis.

  ·  Schistocytes: fragments or broken pieces of RBCs. This may be due to a disorder that is causing the red blood cells to be especially fragile or due to mechanical haemolysis as seen sometimes with devices such as artificial heart valves, or in severely burned patients.

  ·  Spherocytosis: sphere-shaped RBCs found in hereditary spherocytosis or in autoimmune haemolytic anaemia.

  Colour

  ·  Hypochromasia: this may be seen in a variety of disorders including thalassaemia and iron deficiency. The RBC is pale in colour due to insufficient haemoglobin and contains a large, hollow middle (central pallor) of the cell.

  ·  Polychromasia: blue-staining RBCs, indicating that they are immature due to early release from the bone marrow.

  
  

  Intracellular structure (nuclear material, remnants and inclusions inside the RBC)

  
  

  ·  Nucleated RBCs (normoblasts): a very immature form of RBCs seen when there is a severe demand for RBCs to be released by the bone marrow. May be seen in abrupt blood loss, severe anaemia, myelofibrosis, thalassaemia, miliary tuberculosis and in cancers that involve the bone marrow. nucleated RBCs can be normal in infants for a short time after birth.

  ·  Reticulocytes: these are immature RBCs that are usually polychromatic in colour. A few of these young red blood cells are normal in the circulation. Elevated numbers may be seen with acute blood loss, hypoxia, RBC destruction (“haemolysis”, such as in sickle cell disease, glucose-6-phosphate dehydrogenase (G6PD) deficiency and autoimmune haemolytic anaemia).

  ·  Siderocyte, sideroblast, ringed sideroblast: When RBCs are stained with Prussian blue dye, iron granules may be seen. Sideroblasts are immature siderocytes. Ring sideroblasts are particularly found in some forms of hereditary anaemia and in myelodysplastic syndrome.

  ·  Basophilic stippling (dark blue dots inside the RBC): due to the precipitation of nuclear material (ribosomes) and may be present in heavy metal poisoning (such as lead), nutritional deficiencies, or myelofibrosis.

  ·  Heinz bodies: large inclusion bodies (granules) in the RBCs when stained with crystal violet. May be due to an enzyme (G6PD) deficiency, unstable haemoglobin variant, thalassaemia, and autoimmune haemolytic anaemia.

  ·  Howell-Jolly bodies (small round remnants of nuclear DNA inside cell): present in sickle cell anaemia, haemolytic or megaloblastic anaemias, and may be seen after a splenectomy.

  ·  Cabot's Rings: threadlike inclusions that form a ring within the RBC. May be seen in a variety of anaemias.

  ·  Malarial parasites: patients with malaria may have these parasites living inside RBCs breaking them apart as they leave. This is not a routine finding; it would normally only be detected on a blood film when an investigating doctor suspects that a patient has an active case of malaria.