Acute myelomonocytic leukemia (AMML) is a rare form of acute myeloid leukemia (AML). It is the result of increased production of cells called blasts.
AML is a type of leukemia that affects cells that give rise to white blood cells (WBCs) other than lymphocytes. In AMML, there is an overproduction of cells called myeloblasts and promonocytes. In normal circumstances, these cells turn into neutrophils and monocytes.
This rare type of AML occurs in 5–10% of AML cases. AML accounts for only a small amount of all cancers, with only a little over
While it can occur at any age, AMML is more common in older adults. The median age of those with AMML is 50. It affects males slightly more than females.
The overproduction of blasts in the blood marrow prevents the production of healthy blood cells. This results in symptoms such as low platelet count (thrombocytopenia) and low red blood cell count(anemia).
Early symptoms include:
- fatigue
- fever
- weight loss
- dizziness
- weakness or lack of energy
- shortness of breath
A person may also present with paleness, excessive bleeding and bruising, tiny red spots on their skin, frequent infections, and poor healing of minor cuts.
More specific symptoms include:
- swollen gums (gingival hyperplasia)
- swollen lymph nodes (lymphadenopathy)
- enlargement of the spleen and liver (hepatosplenomegaly)
The causes for AMML are unknown. However, specific genetic abnormalities in bone marrow cells cause them to reproduce uncontrollably, leading to leukemia.
Two chromosomal changes linked to AMML are the inversion of chromosome 16 or (inv)16 and the rearrangement of the 11q23 gene.
Aside from physical exams and conducting a thorough medical history, doctors will request blood and bone marrow samples to make a definitive diagnosis of AMML. Tests include:
- Complete blood count with differential: This measures the number of blood cells in the blood, including WBCs.
- Bone marrow biopsy: This checks the number of blood cells in the bone marrow.
- Peripheral blood smear: This looks at the number and appearance of blood cells under a microscope.
With these tests, doctors will check for the following:
- >20% myeloblasts and promonocytes in the bone marrow
- >20% mature neutrophils and their precursors in the bone marrow
- >20% mature monocytes and their precursors in the bone marrow
However, if doctors need to exclude other conditions, they may use immunophenotyping by flow cytometry and chromosome tests. Doctors may check for common chromosomal abnormalities like (inv)16 and rearrangement of the 11q23 gene.
Immunophenotyping identifies the type of WBCs by detecting specific antigens or markers on the surface of cells. Most cases have nonspecific chromosomal abnormalities.
The main goal of treatment for AMML is to achieve and maintain complete remission. A person is in complete remission if they have:
- less than 5% of blasts in the bone marrow
- normal blood cell counts
The primary treatment for people with AMML is chemotherapy.
However, doctors may add targeted therapy drugs or consider stem cell transplants for certain people. Doctors do not typically recommend radiation or surgery to treat AMML.
The treatment for AML has two phases:
Induction
Also called remission induction, this first phase aims to induce remission. Doctors usually give people under age 60 more intensive treatment, while older individuals receive a similar but less intensive treatment.
Treatment includes the chemotherapy drug cytarabine and an anthracycline drug such as daunorubicin. These drugs interfere with the DNA function of WBCs, including the leukemic blast cells.
Consolidation
People in complete remission receive consolidation treatment to help prevent relapse and ideally destroy the remaining leukemic cells.
Depending on the person’s age and health status, doctors may give them several cycles of high-dose chemotherapy.
However, a person older than 60 with a certain health status might not tolerate intensive treatment. Doctors may recommend these people undergo less intensive treatment.
Doctors may recommend hematopoietic stem cell transplantation (HCST) in people who are at a higher risk for relapse due to specific chromosomal abnormalities.
Other treatments
People who do not respond to induction or have relapsed may undergo re-induction therapy using different chemotherapy drugs.
They may also receive supportive treatments to help manage complications and symptoms. These include antibiotics and blood transfusions.
People may also opt to join clinical trials to gain access to novel therapies currently under research.
When first-line induction treatment isn’t successful, this can affect a person’s prognosis. Similarly, people who relapse within 6 months after the induction treatment have a poorer prognosis than those who relapse beyond 6 months.
More than 80% of people younger than 60 respond well to induction therapy, while less than half of people older than 60 go into complete remission. However, this rate may improve with intensive treatment.
Up to half of people with AMML do not have chromosomal abnormalities. People with inv(16) have better clinical outcomes and respond better with treatment. Meanwhile, one 2019 study found that people with abnormalities with chromosome 11 have less favorable results.
People with AMML, like other types of AML, will require close monitoring, whether they have gone into complete remission or are still undergoing treatment.
Learning to live with the condition can be difficult and stressful. Many people with AML deal with emotions like uncertainty and isolation. A
Having the condition is also expensive. A 2019 study found that the average total cost of having AML goes over $400,000, with the bulk spent on in-patient visits and ICU stays. Patients who receive HCST manage higher charges, probably due to more prolonged episodes of care and survival.
AMML is a rare type of AML that presents with abnormalities in two blood cell lines. People must meet specific criteria for doctors to make an AMML diagnosis.
Treatment for AMML is based on a person’s health status, age, the presence of chromosomal abnormalities, and response to therapy. Doctors may also predict their prognosis depending on these same factors.