MLAB 1415: HematologyKeri Brophy-Martinez Anemia Part Three
RBC Shape Variations • Alterations in the shape of the RBC is called poikilocytosis.
Target Cells (Codocytes) • Occur due to an increased red blood cell surface area. • Appear as "targets" on peripheral blood smear. Have a pale central area with most of the hemoglobin around the rim of the cell. • Are always hypochromic.
Target Cells (Codocytes) • Mechanism in formation is related to excess membrane cholesterol and phospholipid, and to decreased cellular hemoglobin. • Osmotic fragility is decreased.
So what is Osmotic Fragility? • It is a test to measure RBC resistance to hemolysis • The quicker the hemolysis occurs, the greater the osmotic fragility • What affects osmotic fragility? • Surface to volume ratio • Cell membrane permeability
Target Cells (Codocytes) • Seen in patients with: • Liver disease • Hemoglobin C Disease or Trait • Post-splenectomy • Iron Deficiency Anemia • Any Hemoglobin Abnormality • Can be artifactual
Spherocytes • Have a low surface-to-volume ratio. • Smaller than normal red cell; hemoglobin relatively concentrated; and, have no area of central pallor. • Shape change is irreversible.
Spherocytes • Several mechanisms for formation, but all involve loss of membrane; aging, antibody coating or genetic defect • Is the final stage for red cells before they are sequestered in the spleen.
Spherocytes • Seen in patients with: • Activated complement • Immune Hemolytic Anemia • Hereditary Spherocytosis • Post-Transfusion
Wait! What is Complement? • Complement refers to a complex set of 14 distinct serum proteins that are involved in three separate pathways of activation. • Major Functions • Promote the inflammatory response by opsonization which enhances susceptibility of coated cells to phagocytosis. • Alter biological membranes to cause direct cell lysis.
Ovalocytes and Elliptocytes • Ovalocytes may appear normochromic or hypochromic; normocytic or microcytic. • Hemoglobin concentrated at both ends • Exact mechanism of formation unknown.
Ovalocytes and Elliptocytes • Ovalocytes associated with: • Myelodysplastic Syndromes • Thalassemias • Megaloblastic Processes • Elliptocytes associated with: • Iron Deficiency Anemia • Hereditary Elliptocytosis • Idiopathic Myelofibrosis
Stomatocytes • Red cell of normal size • Slit-like central area of pallor • Exact mechanism of formation unknown • Usually artifactual • Increased osmotic fragility
Stomatocytes • Associated with following disorders: • Hereditary Stomatocytosis • Hemolytic, Acute Alcoholism • Rh Null Phenotype
Sickle Cells (Drepanocytes) • Have at least one pointed end. • Surface area of cell much greater than normal cell.
Sickle Cells (Drepanocytes) • Low oxygen tension causes hemoglobin to polymerize, forming tubules that line up in bundles to deform cell. • Most sickle cells can revert back to normal shape when oxygenated.
Sickle Cells (Drepanocytes) • Associated with the following disorders: • Sickle Cell Anemia • Hemoglobin C Disease
Acanthocytes • Normal or slightly smaller size • Possess 3-12 thorny projections of uneven length along periphery of cell membrane. • Projections are blunt
Acanthocytes • Specific mechanism of formation unknown. • Contain increased cholesterol-to-phospholipid ratio. • Surface area increased • Susceptible to removal by spleen
Acanthocytes • Possible pathologies include: • Alcohol Intoxication • Pyruvate Kinase Deficiency • Congenital Abetalipoproteinemia • Vitamin E Deficiency • Post-Splenectomy
Fragmented Cells • Includes: • Burr Cells • Helmet Cells • Schistocytes • Fragmentation is defined as a loss of a piece of cell membrane that may or may not contain hemoglobin.
Fragmented Cells • Two pathways that lead to fragmentation: • Alteration of normal fluid circulation (vasculitis, malignant hypertension, heart valve replacement). • Intrinsic defects of red cell that make it less deformable (spherocytes and antibody-covered red cells).
Burr Cells (Echinocytes) • Red cells with 10-30 evenly spaced spicules over the surface of the cell. • Normocytic and normochromic. • In large numbers, are an artifact of sample contamination.
Burr Cells (Echinocytes) • "True" burr cells occur in small numbers in uremia, heart disease, stomach cancer, bleeding peptic ulcers, and in patients with untreated hypothyroidism. • Seen in liver disease, renal disease, and burn patients. • May occur in any situation that causes change in tonicity of intravascular fluid (dehydration).
Helmet Cells (Bite Cells) • Usually have two projections surrounding an empty area of red cell membrane. • Looks as if cell has had a bite taken out of it. • Caused by spleenic pitting and impalement of the RBC on fibrin strands
Helmet Cells (Bite Cells) • In conditions where red cells have large inclusion bodies (such as Heinz bodies • G6PD deficiency • May be seen in patients with pulmonary emboli, and disseminated intravascular coagulation (DIC)
Schistocytes • Extreme cell fragmentation • Cell is missing whole pieces of membrane. • Causes bizarre shapes of red cells.
Schistocytes • Caused by loss of membrane by mechanical means • See in patients with microangiopathic hemolytic anemia, DIC, heart valve surgery, or severe burns.
Teardrop Cells • Appear as pear-shaped cells. Length of tail varies. May be microcytic, normocytic, or macrocytic. • Exact formation process unknown. Commonly seen in red cells that contain large inclusion bodies.
Teardrop Cells • Most commonly seen in idiopathic myelofibrosis, thalassemia, and iron deficiency anemia.
References • Harmening, D. M. (2009). Clinical Hematology and Fundamentals of Hemostasis. Philadelphia: F.A Davis. • McKenzie, S. B., & Williams, J. L. (2010). Clinical Laboratory Hematology . Upper Saddle River: Pearson Education, Inc. • http://www.ezhemeonc.com/index.php/hematological-disorders/ • http://www.wiwe.net/irene/lab/chemheme/heme/microscope/stomatocyte.htm • http://home.ccr.cancer.gov/oncology/oncogenomics/WEBHemOncFiles/Review%20of%20Terms.html