Lecture Notes on Acute Leukemia

Hematopoietic Stem Cells

In acute leukemia, cells lose the ability to differentiate/mature
Results in a buildup of blasts in the bone marrow
Normal blast cell count in bone marrow: 1-2%
Acute leukemia is defined by >20% blast cells in the bone marrow
Symptoms arise from loss of normal cells:
- Anemia (fatigue)
- Thrombocytopenia (bleeding issues)
- Neutropenia (infections)
Rapid onset of symptoms

Blood smear indicators:
- Large immature cells with low cytoplasm
Identifying blast types:
- Lymphoid blasts: Positive nuclear staining for TDT (DNA polymerase)
- Myeloid blasts: Presence of myeloperoxidase (MPO, enzyme)
- Auer rods: Crystallized form of MPO in myeloid blasts

B-cell ALL (B-ALL):
- Common markers: CD10, CD19, CD20
- Treatment: Chemotherapy
- Additional prophylactic treatment for CNS and testes (blood-brain and blood-testes barriers)
- Prognosis based on cytogenetics:
  - Good: t(12;21) translocation (common in children)
  - Poor: t(9;22) translocation (Philadelphia chromosome, common in adults)
T-cell ALL (T-ALL):
- Common markers: Range from CD2 to CD8
- Lack of CD10
- Presents as a thymic mass (mediastinal mass) in teenagers (note mnemonic: T for thymus and T for teens)
- Termed as acute lymphoblastic lymphoma due to mass formation

Indicators:
- Myeloperoxidase (with Auer rods)
Common in adults (ages 50-60)
Subclassification:
- Cytogenetic abnormalities (e.g. acute promyelocytic leukemia)
- Lineage of myeloid blasts
- Surface markers

Acute Promyelocytic Leukemia (APL):
- t(15;17) translocation disrupting retinoic acid receptor
- Treatment: All-trans-retinoic acid (ATRA)
- Risk of disseminated intravascular coagulation (DIC) due to Auer rods
Acute Monocytic Leukemia:
- Lacks myeloperoxidase
- Symptoms: Gum infiltration (swollen gums)
- Subtypes include erythroblastosis and monoblast AML
Acute Megakaryoblastic Leukemia:
- Association with Down syndrome (before age 5)
- Lack of myeloperoxidase