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
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.