Studying The Erythrocyte (RBC) Morphology On Blood Smears

It is important for every medical student and doctor to learn the basic pathology like studying the morphology of normal and abnormal RBC's on blood smears. A brief description is given below.

Normal RBC Morphology: It is about 7.5 micrometer in diameter, roughly the size of a small lymphocyte. All the cells are of same size and color and have lightly colored area in the center.

Reticulocytes: are large, grey blue cells admixed with pink (on Wright's stain). Reticulocyte is actually an immature red blood cell without a nucleus. 

Anisocytosis: variation in RBC size, 

• Normal MCV is 80-100 fl
• large cells imply delay in erythroid precursor DNA synthesis caused by folate or B12 deficiency or as a side effect of medication. Macrocytes MCV > 100fl
• small cells imply a defect in hemoglobin synthesis caused by iron deficiency or abnormal hemoglobin genes. Microcytes MCV < 80 fl 

RWD - the automated rec cell distribution width is a measure of anisocytosis.

Anisocytosis is a feature of most anemias

Poikilocytes: abnormal RBC shapes. They can be of many types and are described below:

• Acanthocytes (spur cells): irregularly spiculated . seen in conditions like abetalipoprotenemia, severe  liver disease and rarely in anorexia nervosa

• Echinocytes (Burr cells): regularly shaped, uniformly distributed spiny projection. Seen in conditions like uremai and RB volume loss. 

• Elliptocytes: elliptical shaped cells seen in hereditary elliptocytosis.

• Schizocytes: fragmented cells of varying size and shape, seen in microangiopathic or macroangiopathic hemolytic anemia. 
  

• Sickled cells: elongated, crescentric, sickle shaped cells seen in sickle cell anemia. 

• Spherocytes: small hyperchromic cells , lacking normal central pallor, seen in hereditary sperocytosis, extravascular hemolysis as in autoimmune hemolytic anemia, G6PD deficiency. 

• Target cells: central and outer rim staining with intervening ring of pallor. seen in liver disease, thalassemia, hemoglobin C and sickle cell disease. 

• Teardrop cells: (dacrocytes) shaped like a tear drop with one side of the cell tapered and the other blunt. seen in myelofibrosis, osteopetrosis and other infiltrative disorders of the bone marrow. 

• Rouleaux formation: alignment of RBCs in stacks of coins, may be artifactual or due to paraproteinemia e.g in multiple myeloma, macroglobulinemia. 

RBC inclusions: Inclusions sometimes also known as elementary bodies are nuclear or cytoplamic aggregates of stainable substances usually proteins. Identifying theses inclusion bodies may sometimes help in diagnosis of certain diseases.

• Howell-Jolly bodies: 1 micrometer diameter basophillic, cytoplasmic inclusions that represents a residual nuclear fragment. seen in asplenic patients.

• Basophillic stippling: multiple, punctate basophillic cytoplasmic inclusions composed of precipitated mitocondria and ribosomes. seen in lead poisoning, thalassemia, myelofibrosis

• Pappenheimer (iron) bodies: iron containing granules usually composed of mitochondria and ribosomes, resemble basophillic stipplingbut also stain with pursian blue, seen in lead poisoning and other sideroblastic anemias. 

• Heinz bodies: spherical inclusions of precipitated hemoglobin seen only with supra vital stains, such as crystal voilet. seen in G6PD deficiency, unstable hemoglobin variants.

• Parasites: characteristic intracytoplasmic inclusions as seen in malaria, babesiosis.