Peripheral Blood Smear

Anisocytosis

Iron Deficiency Anemia (see Iron Deficiency Anemia, [[Iron Deficiency Anemia]])
Thalassemia
- Alpha Thalassemia Minima (see Thalassemias, [[Thalassemias]]): slight hypochromia may be seen
- Alpha Thalassemia Minor (see Thalassemias, [[Thalassemias]])
- Beta Thalassemia Minor (see Thalassemias, [[Thalassemias]])
- Beta Thalassemia Intermedia (see Thalassemias, [[Thalassemias]])
- Beta Thalassemia Major (see Thalassemias, [[Thalassemias]])

Definition: smear with precursor cells of the myeloid and erythroid lineage, which usually indicates the presence of extramedullary hematopoiesis (predominantly in the spleen)
Etiology
- Bone Marrow Infiltration (see Pancytopenia, [[Pancytopenia]])
- Myelofibrosis/Myelophthisis (see Pancytopenia, [[Pancytopenia]])
- Severe Stress
  - Blood Loss
  - Hemolysis
  - Infection
Features
- Anisocytosis: RBC’s are of different sizes
- Immature Myeloid Cells
- Immature Nucleated RBC’s
- Megakaryocytic Fragments
- Poikilocytosis: abnormally-shaped RBC’s
- Polychromasia (Polychromatophilia): large number of grayish-blue RBC’s, indicative of RBC immaturity
- Teardrop-Shaped RBC’s (Dacrocytes)

Definition: fragmented RBC’s
Etiology
- Hemolytic Anemia (see Hemolytic Anemia, [[Hemolytic Anemia]])
  - Thrombotic Thrombocytopenic Purpura (TTP) (see Thrombotic Thrombocytopenic Purpura, [[Thrombotic Thrombocytopenic Purpura]])
  - Hemolytic-Uremic Syndrome (HUS) (see Hemolytic-Uremic Syndrome, [[Hemolytic-Uremic Syndrome]])
  - Mechanical Damage to Red Blood Cells
    - Macroangiopathic Hemolytic Anemia
    - Microangiopathic Hemolytic Anemia (MAHA)

Definition: presence of spherocytes indicates loss of RBC membrane surface area in excess of loss of cell volume -> spherocytes are a feature of many hemolytic anemias
Etiology
- Interaction of Membrane-Antibody Complex with Reticuloendothelial System
  - Autoimmune Hemolytic Anemia (AIHA)
  - Alloimmune Hemolytic Anemia: ABO incompatibility
- Microangiopathic Hemolytic Anemias (MAHA)
- Oxidant Injury
  - Glucose-6-Phosphate Dehydrogenase Deficiency (see Glucose-6-Phosphate Dehydrogenase Deficiency, [[Glucose-6-Phosphate Dehydrogenase Deficiency]])
  - Hemoglobin H Disease
- Phospholipases or Other Membrane Active Enzymes
  - Clostridium Perfringens (see Clostridium Perfringens, [[Clostridium Perfringens]])
  - Venoms
- Othe
  - Hereditary Spherocytosis (Hereditary Spherocytosis, [[Hereditary Spherocytosis]])
  - Severe Hypophosphatemia (see Hypophosphatemia, [[Hypophosphatemia]])

Definition
Etiology
- Asplenia (see Asplenia, [[Asplenia]]): splenic macrophages normally clear opsonized, deformed, and damaged red blood cells -> if splenic macrophage function is abnormal/absent because due to splenectomy, altered red blood cells will not be removed from the circulation appropriately
  - Auto-Splenectomy Resulting from Sickle Cell Disease (see Sickle Cell Disease, [[Sickle Cell Disease]])
  - Post-Splenectomy
- End-Stage Liver Disease (ESLD) (see End-Stage Liver Disease, [[End-Stage Liver Disease]]): decreased lecithin/cholesterol acyltransferase (LCAT) activity, resulting in increased cholesterol:phospholipid ratio -> absolute increase in surface area of the red blood cell membrane
- Hemoglobin C Disease
- Iron Deficiency Anemia (see Iron Deficiency Anemia, [[Iron Deficiency Anemia]]): decrease in hemoglobin content relative to red blood cell surface area
- Thalassemias (see Thalassemias, [[Thalassemias]]): decreased hemoglobin content relative to red blood cell surface area
  - Alpha Thalassemia Minor (see Thalassemias, [[Thalassemias]])
  - Beta Thalassemia Minor (see Thalassemias, [[Thalassemias]])