Acute Myeloid Leukemia
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Introduction
Acute myeloid leukemia (AML) is the most common acute leukemia in adults. It is a disease of blocked differentiation and continuous proliferation of myeloid progenitor cells, which take over bone marrow and lead to acute disease.
There is an incidence of 3/100,000 per year.
The median age of onset is 60-65.
The Case of...
a simple case introducing clincial presentation and calling for a differential diagnosis to get students thinking.
Causes and Risk Factors
Causes and risk factors include:
- ionizing radiation
- chemotherapy
- benzene
- Down syndrome
Pathophysiology
AML represents a rapidly progressive failure of myeloid cells to differentiate past the blast stage. This leads to uncontrolled growth and suppression of normal hematopoiesis through accumulation in the bone marrow.
There are over 8 types of myeloid leukemias.
M3 - promyelocytic
- common-ish
APL
- better prognosis
- less intesive therapy
- differentiation therapy - All trans retinoic acid
- arsenic dioxide
Transcription of differentiation is inhibited by AML/ETO fusion protein and recruitment of repressors
monosomy 7
RAEB
Signs and Symptoms
- history
- physical exam
History
AML has a short onset of days to weeks.
- fever and fatigue, mimicking the flu (anemia)
- bruising, petichiae, mucosal bleeding (thrombocytopenia)
- infection (neutropenia)
- skeletal pain
- skin infiltration (Sweet syndrome)
Physical Exam
Splenomegaly may be evident.
Skin examination can reveal purpura or petechiae.
Gingival hypertrophy may be present.
Investigations
- lab investigations
- diagnostic imaging
Lab Investigations
Complete blood count
- anemia with normal or elevated MCV
- high or low white count, with at least 30% of WBC being blasts
- thrombocytopenia
Increased uric acid
Renal function tests - increased WBC can damage kidneys
Peripheral smear
- blast cells
- Auer rods (coalescence of primary granules) are present in myeloid blasts but not lymphoid blasts
Bone marrow biopsy
- blasts occupy at least 20% of bone marrow
- faggot cell
Diagnostic Imaging
Differential Diagnosis
Treatments
As AML is a rapidly life-threatening emergency, treatment must begin immediately. Long-term hospitalization is the norm. There is a high risk of severe infection, with multiple ICU admissions.
Chemotherapy is given first for induction and then consolidation, often in 5 intensive blocks over 6 months.
Consequences and Course
Hyperleukocytosis can cause renal failure and DIC.
- overall survival ~65%
- toxic deaths more common than ALL
- relapse = poor prognosis
Resources and References
Topic Development
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