Notes on White Blood Cell Disorders and Pathophysiology

Overview of White Blood Cells (WBCs)

  • WBCs (Leukocytes): Protect against infections.
  • Categories:
    • Bone Marrow Roles:
    • Produces WBCs, RBCs, and platelets.
    • Immunities:
    • Innate Immunity: 1st line of defense (e.g., neutrophils, macrophages).
    • Adaptive Immunity: Specific, acquired (e.g., B and T lymphocytes, memory cells).

WBC Disorders

  • Leukemia:
    • Characterized by uncontrolled proliferation of cancerous WBCs.
    • 90% of cases are adults.
    • 3rd most common cancer in children.
  • Lymphoma:
    • Solid tumors of lymphoid cells (e.g., T and B cells).
    • Types: Hodgkin's and Non-Hodgkin's lymphoma.
  • Myelodysplastic Syndrome (MDS):
    • Dysplastic development of stem cells in bone marrow.
  • Multiple Myeloma:
    • Excessive proliferation of plasma cells secrete immunoglobulins (Igs).

Major Categories of WBCs

  • Monocytes:
    • Mature into macrophages and are part of agranulocytes (2-10% of circulating WBCs).
  • Lymphocytes:
    • T and B cells (20-40% of circulating WBCs), provide long-term immunity.
  • Granulocytes:
    • Types include basophils, eosinophils, neutrophils.
    • Neutrophils: Most numerous; first responders during infection.

Hematopoiesis: Blood Cell Formation

  • Process: Pluripotent stem cells in bone marrow differentiate into various blood cells.
    • Myeloid Stem Cells: Give rise to granulocytes and monocytes.
    • Lymphoid Stem Cells: Differentiate into T and B cells.

Synthesis and Maturation of WBCs

  • WBC Formation:
    • Stem cells in the bone marrow produce WBCs.
    • Blast Cells: Immature precursor cells that develop into various WBCs (neutrophils, monocytes, lymphocytes).

Alterations in WBC Numbers

  • Leukocytosis: WBC count above 11,000 cells/microliter.
  • Leukopenia: WBC count below 4,000 cells/microliter.
  • Neutrophilia: Elevation of neutrophils, often due to bacterial infections.
  • Neutropenia: Below 1,500 neutrophils/microliter; compromises immune response.

Clinical Concepts Related to Disorders

  • Tumor Lysis Syndrome:
    • Occurs post-cancer therapy, causing complications like acute kidney injury.
  • Myelocytic Leukemia: Type of leukemia impacting myeloid stem cells.
  • Lymphoma Risks: Can pressure surrounding organs based on location (e.g., trachea).

Multiple Myeloma (MM)

  • Nature: Abnormal production of immunoglobulins by plasma B cells.
  • Diagnosis: At least 10% plasma cells in the marrow, symptoms like bone pain and renal disease.
  • Treatment: Managed through a combination of therapies including stem cell transplant.

Lymphoma Types

  • Hodgkin’s Lymphoma:
    • Characterized by Reed-Sternberg cells, common among adolescents and young adults.
  • Non-Hodgkin’s Lymphoma:
    • More common, presents with painless lymph node enlargement, diverse subtypes.

Diagnosis and Treatment of Hematological Neoplasms

  • Diagnosis Tools: CBC with differential, bone marrow aspiration, cytogenetic testing, etc.
  • Treatment Options: Chemotherapy, radiation, stem cell transplant, CAR-T therapy for acute leukemias.
  • Treatment Complications: Conditions such as tumor lysis syndrome and differentiation syndrome.

Summary of Leukemia Types and Their Characteristics

  1. Acute Lymphoblastic Leukemia (ALL): Common in children; aggressive; treatment involves multidrug regimens.
  2. Chronic Lymphocytic Leukemia (CLL): Most common in adults over 70; presents with elevated WBC counts.
  3. Acute Myelogenous Leukemia (AML): Characterized by high myeloblast levels in the marrow.
  4. Chronic Myelogenous Leukemia (CML): Associated with the Philadelphia chromosome, treatment often involves TKIs.

Conclusion

  • WBC disorders encompass a broad spectrum of conditions impacting immune function, with various causes, presentations, and treatments. Understanding these elements is crucial for effective assessment and intervention in clinical settings.