Lecture Notes: Hematopoiesis and Leukemia

Hematopoietic Process

• Hematopoietic Stem Cells: All blood cells originate from hematopoietic stem cells (hemocytoblasts).

• Differentiation:

  • Myeloid Stem Cells: Differentiate into major red cells, white cells, and platelets (excluding lymphocytes).
  • Lymphoid Stem Cells: Differentiate into lymphoblasts and subsequently lymphocytes.

• Lineage Differences:

  • Lymphocytes: Derived from lymphoid stem cells.
  • Other Cells: Derived from myeloid stem cells.

• Location of Maturation:

  • Myeloid-derived Cells: Typically mature in the bone marrow.
  • Lymphoid-derived Cells: Some mature in the bone marrow; others migrate to organs like the thymus (T-cells) and lymph nodes.

Leukemia Overview

• Definition: Malignant disorders of blood or bone marrow with uncontrolled proliferation of leukocytes.

• Four Major Types:

  • ALL: Acute Lymphocytic Leukemia
  • AML: Acute Myelocytic Leukemia
  • CLL: Chronic Lymphocytic Leukemia
  • CML: Chronic Myelocytic Leukemia

• Acute vs. Chronic:

  • Acute Leukemias:

    • Rapid progression.
    • High number of blast cells (immature cells).
    • Immediate treatment required.
    • ALL vs. AML determined by predominance of lymphoblasts or myeloblasts.

  • Chronic Leukemias:

    • Slower progression.
    • Presence of mature but abnormal cells.

Acute Leukemia Pathophysiology

• Accumulation of Blast Cells:

  • Overcrowding in the bone marrow.
  • Suppresses normal hematopoiesis.

• Consequences:

  • Pancytopenia: Low counts of red cells, white cells, and platelets.
  • Anemia: Due to decreased red blood cells.
  • Neutropenia: Low neutrophil count.
  • Thrombocytopenia: Low platelet count, leading to bleeding risks.

• Symptoms:

  • Bone and joint pain due to overcrowding.
  • Hyper metabolism leading to weight loss.
  • Potential for severe weight loss and cachexia over time.

Diagnosis

• Tests:

  • Complete Blood Count (CBC): To identify abnormalities in blood cell counts.
  • Bone Marrow Biopsy: Essential for diagnosis, especially to identify excess myeloblasts (AML) or lymphoblasts (ALL).

• Special Note: Presence of Auer rods in one type of AML, which is associated with vitamin A.