Hematologic & Immunologic Diseases PowerPoint

Hematologic & Immunologic Diseases Study Notes

Objectives

  • After this lesson, you will be able to:
    • List hematologic and immunologic diseases.
    • Discuss associated diagnostics.
    • Discuss treatments.

Terminology - Abbreviations

  • CBC: Complete Blood Count
  • WBC: White Blood Cell
  • PMN: Polymorphonucleocyte
  • Hct: Hematocrit
  • Hb: Hemoglobin
  • MCV: Mean Corpuscular Volume
  • MCH: Mean Corpuscular Hemoglobin
  • MCHC: Mean Corpuscular Hemoglobin Concentration
  • NRBC: Nucleated Red Blood Cell
  • EDTA: Ethylenediamine Tetra-acetic Acid

Root Words

  • Erythr/o: Red
  • Leuk/o: White
  • Thromb/o: Clot
  • Poikil/o: Irregular
  • Acanth/o: Spiny

Review: Red Blood Cells (RBCs)

  • Function: Carry oxygen from lungs to cells and remove carbon dioxide and waste products.
  • Lifespan: Approximately 120 days; filtered out of circulation by macrophages in spleen and liver.
  • Production: Constantly created by the bone marrow to replace old RBCs.

Diagnostics for Hematologic & Immunologic Diseases

Packed Cell Volume (PCV)
  • Measurement of the proportion of blood made up of red blood cells, expressed as a percentage or fraction of cells in blood.
Complete Blood Count (CBC)
  • Provides detailed information about red blood cells, white blood cells, and platelets.
Blood Smear
  • Used to identify:
    • Red blood parasites,
    • Abnormal cells indicating leukemia,
    • Indications of Immune-Mediated Hemolytic Anemia (IMHA) or other damages to cells.
Bone Marrow Aspirate
  • Performed under sedation or anesthesia.
  • Aids in diagnosing bone marrow diseases.
  • Red marrow persists in sternum throughout life; commonly collected from:
    • Humerus,
    • Femur,
    • Pelvis bones.
Blood Chemistries and Urinalysis (UA)
  • Evaluates organ function, electrolyte levels, overall health.
  • Kidney diseases can affect the bone marrow.
Fecal Exam
  • Identifies parasites in the intestinal tract that might be causing blood loss, e.g., hookworms.
Imaging
  • Used to look for metastatic diseases or underlying problems.
  • Modalities include:
    • Radiographs,
    • Ultrasound.
FeLV/FIV Testing
  • Test window includes test and control spots, activation circle, and sample well.
  • SNAP test for in-house; can also be sent to reference laboratories.
Tick Testing
  • Some diseases can be tested in-house via SNAP tests; others at reference labs through serology or PCR tests.

Erythrocyte Disorders

Categories of Erythrocyte Disorders

  1. Inappropriate loss: Hemorrhage

    • Causes include trauma, rat bait ingestion/coagulopathies, severe internal bleeding.
    • In cases of acute loss, the PCV may not reflect the severity of anemia. If the anemia is present for 3-5 days, reticulocytes should be expected.
    • Treatment:
    • Replenishing volume (crystalloid fluids)
    • Replacing RBCs (transfusions)
    • Stopping cause of blood loss.

  2. Decreased production:

    • Causes include chronic blood loss, severe flea infestations, intestinal parasites, ulcers, bleeding neoplasia.
    • Altered RBCs present as microcytic (small) and hypochromic.
    • Treatment: Address inciting cause; iron supplementation for 30-60 days may be required; once parasites treated, the body will rebuild RBC supply.

  3. Increased destruction (Hemolysis):

    • Causes include immune-mediated hemolytic anemia (IMHA), Mycoplasma haemofelis, and Heinz body anemia.
    • Symptoms include exercise intolerance, pale mucous membranes, tachycardia, and icterus (jaundice).
    • Treatment: Suppress immune system, blood transfusions may be necessary in severe cases.
Specific Erythrocyte Disorders

  1. Blood-borne Parasites:

    • Mycoplasma Haemofelis: Common in cats; attaches to RBCs and causes anemia.
    • Transmission: Biting, blood-sucking parasites (fleas), bite wounds, mother to fetus.
    • Other parasites: Babesia canis, Babesia gibsoni (transmitted by brown dog tick), Cytauxzoon felix.
    • Clinical Signs: Weight loss, anorexia, fever, hepatomegaly, splenomegaly, dehydration, icterus.
    • Diagnosis: Finding intracellular parasites on blood smear, PCR or serology testing for specific pathogens.
    • Treatment: Antibiotic therapy (e.g., tetracycline or doxycycline), supportive care.

  2. Toxin-Induced and Heinz Body Anemias:

    • Heinz bodies: Dense round granules at the periphery of RBCs stained with new methylene blue.
    • Clinical Signs: Exposure to onions, Tylenol, zinc.
    • Symptoms include sudden weakness, decreased appetite, reddish-brown urine (in severe cases), pale mucous membranes.
    • Diagnosis: CBC, blood smear with new methylene blue.
    • Treatment: Address underlying cause; severe anemia may necessitate hospitalization with oxygen therapy and blood transfusions.

  3. Immune-Mediated Hemolytic Anemia (IMHA):

    • Immune system attacks red blood cells due to antibodies attached to RBC membrane.
    • Primary IMHA: More common in dogs (Cocker Spaniels, Springer Spaniels, Poodles) with no underlying cause.
    • Secondary IMHA: Triggered by underlying conditions, medications, or vaccines; more common in cats.
    • Clinical Signs: Anorexia, weakness/depression, fever, tachycardia, icterus, pale/yellow mucous membranes, hemoglobin in urine (port-wine colored).
    • Diagnosis: CBC shows anemia/inflammatory leukogram, blood smear showing spherocytes/ghost cells, serum chemistries may show elevated bilirubin/liver enzymes.
    • Treatment: Immunosuppression (glucocorticoids), blood transfusions, GI protectants for possible ulcers, thromboprophylaxis therapy (e.g., heparin).
    • Prognosis: Poor; approximately 30-40% mortality rate despite aggressive therapy.

Thrombocyte Disorders

Immune-Mediated Thrombocytopenia (IMTP or ITP)
  • Platelets coated with antibodies, leading to their destruction.
  • Risk factors: Middle-aged females, cocker spaniels predisposed.
  • Clinical Signs: Petechiae, ecchymosis, bleeding from gums, nose, bladder, GI tract, unexpected weakness, fever.
  • Diagnosis: CBC shows low platelets, chest radiographs (met check), abdominal ultrasound for neoplasia.
  • Treatment:
    • Immunosuppression (glucocorticoids + another immunosuppressive agent)
    • Possible use of Vincristine or IV immunoglobulin
    • Blood transfusions (freshly collected preferred)
    • Prognosis: Guarded to poor, approximately 20% mortality rate, potential for relapses.
Disseminated Intravascular Coagulation (DIC)
  • Condition causing many clots in the vascular system leading to bleeding into tissues.
  • Causes include blood transfusion reactions, cancer (certain leukemias), pancreatitis, septicemia, and certain inflammatory conditions.
  • Expected outcome often leads to euthanasia due to severe systemic compromise.
Warfarin/Brodifacoum Poisoning
  • Rat-bait intended for ingestion, has a sweet taste, and inhibits clotting factors by antagonizing Vitamin K.

Leukocyte Disorders

Overview of White Blood Cells
  • Types of leukocytes:
    • Granulocytes: Neutrophils, basophils, eosinophils
    • Agranulocytes: T-lymphocytes, B-lymphocytes, monocytes
Ehrlichiosis
  • A rickettsial disease attacking white blood cells in dogs.
  • Transmission via the Brown Dog tick.
  • Clinical Signs: Acute (depression, anorexia, fever, weight loss) and chronic (bleeding, severe weight loss, anterior uveitis).
  • Diagnosis: Pancytopenia, aplastic anemia, thrombocytopenia, positive Coombs test, blood smear evaluation, IFA test.
  • Treatment: Tetracycline or doxycycline.
Feline Lymphoma
  • Cancer of lymphocytes, can be primary or secondary to Feline Leukemia Virus (FeLV).
  • Common sites: Intestinal lymphoma, mediastinal lymphoma, renal lymphoma
  • Clinical Signs: Weight loss, chronic vomiting, diarrhea, anorexia.
  • Diagnosis: Cytology/histopathology, general blood work, chest radiographs, abdominal ultrasound, FeLV/FIV testing.
  • Treatment: Usually chemotherapy, with surgery or radiation for localized disease, prednisone for supportive care.
Canine Lymphoma
  • Most common in middle-aged and older dogs with types including multicentric, alimentary, mediastinal, and extranodal.
  • Diagnosis: Cytology/biopsy, immuno-histochemistries to distinguish between B-cell and T-cell origin.
  • Stages of lymphoma:
    • Stage I: Single lymph node.
    • Stage II: Lymph nodes on one side of the diaphragm.
    • Stage III: Generalized lymph node involvement.
    • Stage IV: Liver and/or spleen involvement.
    • Stage V: Bone marrow, nervous system, or unusual locations.
  • Treatment: Chemotherapy (e.g., Madison-Wisconsin protocol), surgery, radiation, and prednisone for palliative care.
Feline Immunodeficiency Virus (FIV)
  • Spread through bite wounds, blood transfusions, and during pregnancy/lactation.
  • Cats remain infected for life with clinical signs appearing years later related to secondary infections.
  • Clinical Signs: Many asymptomatic for years; when symptomatic, may show weight loss, poor appetite, fever.
  • Diagnosis: ELISA for antibodies, with false positives possible from vaccination.
  • Treatment: Supportive care for secondary infections.

Clotting Cascade Disorders

Common Clotting Disorders
  • Bruise (contusion): Injury not breaking skin but causing blood effusion into subcutaneous tissue (hematoma).
  • Petechia: Small, pinpoint purplish hemorrhagic spots on skin/mucous membranes.
  • Ecchymosis: Larger areas of hemorrhage showing skin discoloration.
  • Purpura: Hemorrhages into skin that change color over time (red to brownish-yellow).
History & Clinical Signs
  • Assessment of first bleeding episode, prior surgeries, vaccinations, medications, or rodenticides.
  • Clinical signs include petechiae, hematomas, bleeding from mucous membranes and body cavities, and prolonged clotting times.
Diagnostic Tests for Clotting
  • Tests include platelet estimates/count, coagulation times (PT, PTT), and BMBT (Buccal Mucosal Bleeding Time).
Patient Management
  • Management strategies entail minimizing trauma, using small needle gauges, applying prolonged pressure after venipuncture, avoiding invasive procedures, and potential transfusions.

Von Willebrand Disease (vWD)

  • Most common inherited disorder causing decreased von Willebrand factor leading to prolonged bleeding.
  • Breeds predisposed include Dobermans, German Shepherds, and Labrador Retrievers.
  • Genetic inheritance: Autosomal dominant with incomplete penetrance.
  • Diagnosis: Buccal mucosal bleeding time (BMBT), vWF level assessment.
  • Treatment: Plasma/cryoprecipitate infusion or desmopressin acetate (administer 1 mcg/kg SQ 30 minutes before surgery).
  • Importantly, do not breed dogs carrying the gene.

Immunologic Tests

Types and Purposes
  • SNAP Tests: Common in-house tests for diseases, some measure IgG, indicating previous exposure.
  • Antigen Tests: Indicate the presence of infectious agents in the body without measuring antibodies.
  • Antibody Titers: Measure plasma IgG levels; however, does not evaluate cellular immunity.
  • Paired Antibody Titers: First sample establishes a baseline, with a second sample checking for an increase indicating active humoral response.

The Immune System

Overview
  • Immunodeficiency: Inadequate immune function leading to increased susceptibility.
  • Hypersensitivity: Overactive immune response can lead to allergies or autoimmune diseases.
Types of Hypersensitivity
  1. Type I - Immediate Hypersensitivity: Rapid response (5-15 minutes); examples include anaphylaxis.
  2. Type II - Cytotoxic Hypersensitivity: Immune response against the body’s own cells, e.g., penicillin reaction.
  3. Type III - Immune Complex Hypersensitivity: Damage due to immune complexes in tissues.
  4. Type IV - Delayed Type Hypersensitivity: Reaction takes 2-3 days to develop, involving sensitized T lymphocytes (e.g., contact dermatitis).
Autoimmune Diseases
  • The immune system attacks the body’s own tissues. Examples include:
    • Type I Diabetes: Attack on pancreatic insulin cells.
    • Addison’s Disease: Attack on adrenal glands.
    • Autoimmune Thyroiditis: Affecting the thyroid gland.
    • Myasthenia Gravis: Targets muscle/nerve junctions.
    • Systemic Lupus Erythematosus (SLE): Affects small blood vessels throughout the body.
    • Rheumatoid Arthritis (RA): Impacts joints.
Immunotherapy
  • Suppression Immunotherapy: Short-term therapy for hypersensitivities or autoimmune diseases using corticosteroids to inhibit immune function.
  • Activation Immunotherapy: Aims at inducing/enhancing immune responses; standard vaccines create immunologic memory against pathogens.
  • Natural products: Immunoregulin or extracts from Propionibacterium acnes to increase T-cell activity (controversial).
Questions
  • Review all highlighted topics and ensure clarity in understanding processes, diagnostics, and treatments discussed throughout these notes.