Unit 4 WBC Disorders

LEUKOCYTE (WBC) DISORDERS

INTRODUCTION

  • Overview of the document based on white blood cell (WBC) disorders

TERMINOLOGY

  • Suffixes to Remember:

    • -philia: Indicates an increase in cell numbers.

    • -cytosis: Can mean an increase in cell numbers, associated with a disease process.

    • -penia: Indicates a decrease in cell numbers.

DEFINITIONS

  • Leukocytosis:

    • Definition: An increase in the number of WBCs in circulation beyond the reference range, caused by various factors.

    • Significance: Indicates a sum of all WBCs present in circulation, indicating possible immune response or disease process.

  • Leukopenia:

    • Definition: A reduction in the number of WBCs in circulation.

  • Left Shift:

    • Definition: Increased presence of immature WBCs in the bloodstream (e.g., Band cells).

    • Important Note: In most species, since neutrophils constitute the majority of circulating WBCs, they predominantly determine the presence of a Left Shift.

LEFT SHIFT AND NEUTROPHIL POPULATION

  • Image and reference to canine blood illustrating immature neutrophils (Band Neutrophil).

  • Implication: Higher immature cell counts indicate a higher demand for WBCs in circulation.

TYPES OF LEFT SHIFT

  • Classification: Left Shift can be classified as:

    • Regenerative Left Shift:

    • Increased total white blood cell count with immature cells present, mainly characterized by mature cells outnumbering immature ones.

    • Represents an early response to increased demand for WBCs.

    • Degenerative Left Shift:

    • Characterized by normal or low total WBC count, with immature cells outnumbering mature cells.

    • Usually indicates a prolonged condition, potentially due to severe infection or sepsis and presence of toxic changes.

CELL COUNT EXAMPLES (CBC VALUES)

  • Reference ranges for various blood components identified:

    • Erythrocytes (RBC):

    • Value: 5.9

    • Reference Range: 5.5 - 8.5

    • Leukocytes (WBC):

    • Value: 53.7

    • Reference Range: 6.0 – 17.1

    • Neutrophils:

    • Value: 47.26

    • Reference Range: 3.6 – 11.5

    • Other Values: Hgb, Hct, MCV, MCH, MCHC, RDW, Platelets, and Eosinophils all provided with respective values and reference ranges.

    • Indications provided for clumped leukocytosis and neutrophilia.

NEUTROPHILIA WITH LEFT SHIFT

  • Reinforces values from the previous section, indicating clumped neutrophilia with a left shift present.

SPECIES DIFFERENCES

  • Variations among Species:

    • Dogs and Cats:

    • Predominantly exhibit left shift due to a larger pool of WBCs in the bone marrow maturation pool.

    • Cattle and Horses:

    • Display smaller maturation pools in bone marrow, leading to quicker exhaustion of cells and pronounced leukopenia.

    • Do not exhibit the same left shift characteristics.

TOXIC CHANGES IN NEUTROPHILS

  • When immature cells are present in circulation, indicate a left shift that shows toxic changes including:

    1. Cytoplasmic Basophilia

    2. Toxic Granulation

    3. Toxic Vacuolation

    4. Dohle Bodies: Remnants indicating cytoplasmic immaturity, most commonly observed in cats.

    5. Nuclear Immaturity: Juvenile characteristics observed.

  • Importance of assessing each toxic change to determine disease presence.

QUANTITATIVE WBC DISORDERS

  • Abnormalities in leukocyte (WBC) number can be categorized:

    1. Benign Changes: Often represent a good immune response (e.g., neutrophilia in response to infection).

    2. Malignant Changes: Indicate abnormal cell production (e.g., leukemia).

MARGINATION OF LEUKOCYTES

  • Neutrophils exhibit a tendency to become sticky and adhere to blood vessel walls prior to migration into tissues, referred to as the marginated pool.

NEUTROPHILIA

  • Definition: Increase in absolute neutrophil count above normal.

  • Possible Causes:

    1. Short-term physiological stress from epinephrine (30 to 60 minutes).

    2. Prolonged corticosteroid stress (hours to days).

    3. Inflammation due to tissue demand or infection, commonly leading to significant increases in neutrophil counts.

  • Important Note: Neutrophilia is not synonymous with infection alone.

PHYSIOLOGIC NEUTROPHILIA

  • Occurs due to endogenous epinephrine release, causing neutrophils to shift from marginated to circulating pools temporarily, resulting in increased neutrophil counts.

  • Usually a mild, transient response without left shift or toxic changes observed.

STRESS NEUTROPHILIA

  • Caused by sustained corticosteroid release (e.g., Cushing's disease).

  • Results in an increase of neutrophils that do not migrate effectively into tissues due to altered stickiness, leading to difficulty in resolving infections efficiently.

  • Associated conditions can include a stress leukogram characterized by:

    • Neutrophilia

    • Lymphopenia

    • Eosinopenia

INFLAMMATORY NEUTROPHILIA

  • A direct response to an increase in demand for phagocytic cells in tissues.

  • Indicators include:

    • Neutrophilia

    • Possible left shift

    • Possible toxic changes

    • Monocytosis

  • Symptoms may suggest underlying conditions requiring further analysis and treatment.

NEUTROPENIA AND LEFT SHIFT IN DOGS AND CATS

  • Neutropenia with a left shift typically indicates overwhelming inflammation where bone marrow struggles to meet demand; often seen as concerning.

NEUTROPENIA DUE TO INCREASED DEMAND

  • Results from acute infection or severe inflammation where the bone marrow cannot keep up with the increased need for neutrophils.

NEUTROPENIA DUE TO REDUCED PRODUCTION

  • Failure of the bone marrow to produce sufficient neutrophils leading to potential severe consequences.

NEUTROPENIA DUE TO INEFFECTIVE PRODUCTION

  • Cells may be produced but are not released into circulation due to issues within the bone marrow.

NEUTROPENIA - SEQUESTRATION

  • Temporary migration of neutrophils to the marginated pool due to conditions such as anaphylactic shock or endotoxemia, leading to a deceptive drop in neutrophil counts.

MALIGNANT DISORDERS AFFECTING WBCs

  • Leukemia: Characterized by abnormal proliferation of WBCs with increased, immature cell counts.

    • Variation in cell and nucleus size can indicate a cancerous process.

LYMPHOPROLIFERATIVE DISORDERS

  • Definition: Malignant proliferation of lymphoid cells.

    • Malignant lymphoma or lymphosarcoma: Can present as swollen peripheral lymph nodes, with varying WBC counts.

    • Oftentimes requires biopsy or histological evaluation to confirm.

CLINICAL CASE DISCUSSION

  • Clinical scenarios including bloodwork analysis for various conditions are discussed, interpreting CBC results and respective responses through a series of atypical presentations and potential interventions.