Case Study: Acute Myeloid Leukemia (AML)

Patient Presentation

• Patient: 45-year-old man
• Symptoms: Fever (acute onset), fatigue, bone pain, gum bleeding
• Examinations:
  • External: gum bleeding, thermal tenderness
  • Laboratory findings:
    • Hemoglobin: Low (indicative of anemia)
    • WBC count: High (possible infection)
    • Platelet count: Very low (50,000)
• Peripheral Blood Smear: Presence of Auer rods

Diagnosis

• Condition: Acute Myeloid Leukemia (AML)
  • Presence of Auer rods in myeloblasts confirms AML.
  • Differential diagnosis excludes chronic myeloid leukemia (CML) as CML lacks Auer rods.

Classification of AML

• WHO Classification:
  • Acute myeloid leukemia with genetic abnormalities (e.g., translocations 8;21, inv(16), t(15;17))
  • AML with myelodysplasia-related changes
  • Therapy-related AML
  • AML not otherwise classified (Refer to FAB classification)
• FAB Classification:
  • M0: Minimally differentiated
  • M1: Without maturation
  • M2: With maturation
  • M4: Myelomonocytic
  • M5: Monoblastic/Monocytic (M5a and M5b)
  • M6: Erythroid
  • M7: Megakaryoblastic
  • Notably, M1, M2, M4, M6 are Myeloperoxidase positive.

Specific Cytochemical Stains

• Myeloperoxidase (MPO): Positive in immature myeloid cells containing granules and Auer rods. Negative in M0 myeloblast.
• Sudan Black B: Positive in immature cells in AML.
• Periodic Acid-Schiff (PAS): Positive in immature lymphoid cells and erythroid leukemia cells.
• Non-Specific Esterase: Positive in monocytic series (M4 and M5).
• Acid Phosphatase: Shows focal positivity in leukemic blasts and diffuse reaction in monocytic cells; also positive in Acute Lymphoblastic Leukemia (ALL).

Important Points

• Fever and acute onset symptoms lead towards a differential diagnosis involving infections and leukemia.
• Peripheral smears with Auer rods make a strong case for AML diagnosis.
• High WBC count with anemia and low platelets are critical laboratory findings supporting AML.
• WHO and FAB classifications provide a detailed subclassification of different AML types based on genetic and morphological criteria.
• Understanding cytochemical stains is crucial for the differential diagnosis and confirmation of AML subtypes.