Overview
Definition
A clonal hematopoietic neoplasm characterized by the rapid proliferation and accumulation of abnormal, immature myeloid cells (myeloblasts) in the bone marrow and peripheral blood, leading to bone marrow failure.
Epidemiology
The most common acute leukemia in adults. Incidence increases with age. Associated with prior radiation, chemotherapy, or MDS.
Etiology & Risk Factors
- Acquired genetic mutations (FLT3, NPM1, DNMT3A, t(15;17)) causing block in differentiation and uncontrolled cell division
Clinical Symptoms
- Abrupt onset of fatigue, pallor, and dyspnea (anemia)
- Fever and recurrent infections (neutropenia)
- Easy bruising, petechiae, and epistaxis (thrombocytopenia)
- Bone pain
- Gingival hyperplasia (classic in acute monocytic leukemia)
Clinical Approach
Diagnosis
- CBC showing circulating blasts
- Bone marrow biopsy showing >= 20% myeloblasts
- Presence of Auer rods (needle-like azurophilic granules) in blasts (pathognomonic)
- Cytogenetics and molecular testing (drives prognosis and treatment)
Management
- Induction chemotherapy (typically '7+3' regimen: Cytarabine + Anthracycline)
- Consolidation chemotherapy or Allogeneic Stem Cell Transplantation
- All-trans retinoic acid (ATRA) + arsenic trioxide for Acute Promyelocytic Leukemia (APL, t(15;17))
Complications
- Tumor Lysis Syndrome
- Disseminated Intravascular Coagulation (DIC, extremely high risk in APL)
- Neutropenic fever / Sepsis
- Leukostasis (respiratory distress, CNS ischemia from high blast count)