Acute megakaryoblastic leukemia (AMKL), also called acute megakaryocytic leukemia, is a very rare type of blood cancer that most often affects children. About 1 percent of all pediatric leukemias are AMKL. However, adults can also develop this disease. Acute megakaryoblastic leukemia often occurs in people with Down syndrome (DS), a genetic disorder.

What Is Acute Megakaryoblastic Leukemia?

AMKL is a type of acute myeloid leukemia (AML). AML develops from parent cells that produce specific blood cells, including myeloid cells (neutrophils, monocytes, and certain other types of white blood cells), red blood cells, and megakaryocytes.

AMKL affects megakaryocytes, large cells that live in the bone marrow tissue found inside of certain bones. Megakaryocytes produce platelets. Platelets are small fragments that travel through the blood, helping form blood clots and prevent bleeding when you become injured. People with AMKL make too many megakaryoblasts (immature, abnormal forms of megakaryocytes).

Traditionally, acute myeloid leukemia was divided into subtypes using the French-American-British (FAB) classification system. Under this system, AMKL is called AML-M7. More recently, the World Health Organization (WHO) has come up with a different classification method that divides up AML. Scientists have identified multiple different fusion genes, as well as other gene changes, that can lead to non-DS-AMKL.

Signs and Symptoms of AMKL

People with acute megakaryoblastic leukemia often have abnormal levels of different blood cells. This condition can lead to a variety of complications:

• Anemia
• Thrombocytopenia
• Abnormal white blood cell levels
• Myelofibrosis

Anemia

Reduced levels of red blood cells (anemia) can cause pale skin, dizziness, feelings of weakness, headache, ringing in the ears, shortness of breath, or heart failure.

Thrombocytopenia

Low levels of platelets (thrombocytopenia) can lead to bruising, nosebleeds, bleeding gums, blood in the stool, or heavy periods.

Abnormal White Blood Cell Levels

Abnormal levels of white blood cells can cause fever and frequent infections, as well as neurological symptoms like headaches, nausea, vomiting, sensitivity to light, vision problems, or stiffness in the neck.

Myelofibrosis

People with AMKL often have myelofibrosis, a condition in which scar tissue builds up in the bone marrow. Myelofibrosis makes it difficult for the bone marrow to make new, healthy blood cells.

Diagnosis of Acute Megakaryoblastic Leukemia

Doctors use blood and bone marrow samples to diagnose acute megakaryoblastic leukemia. Blood samples can be taken from a regular blood draw, in which a technician removes blood from your arm with a needle and syringe. Bone marrow samples can be taken by inserting a needle into the hip or breast bone and removing different types of tissue. A bone marrow biopsy takes a sample of bone and cells. A bone marrow aspirate takes a sample of bone marrow fluid.

Doctors will count how many immature megakaryoblast cells appear in your bone marrow samples. Under the FAB classification system, you have AMKL if more than 30 percent of your bone marrow cells are blasts. Under the WHO system, you need to have 20 percent blasts to qualify for an AMKL diagnosis.

Your doctor will send your blood and bone marrow cells to a laboratory to undergo testing. During immunophenotyping tests, specialists look for proteins found on the surface of your cells. Because different blood cancer cells make different proteins, knowing which type of proteins are on your cells tells your doctor which type of blood cancer you have. AMKL cells often have CD13, CD33, CD41, CD42, CD61, and factor VIII proteins on their surface. Laboratory specialists perform immunophenotyping by looking at cells under a microscope or by using a procedure called flow cytometry. During flow cytometry, a machine separates and counts different types of cells.

Cytogenetic tests can also help diagnose AMKL. Cytogenetic tests identify any gene changes found within AMKL cells, such as chromosome translocations.

Your doctor may also recommend imaging tests, including X-ray, ultrasound, computed tomography (CT) scans, and magnetic resonance imaging (MRI). Imaging tests can help your doctor see whether leukemia is affecting the function of any of your organs.

Treatment for Acute Megakaryoblastic Leukemia

Different groups of people with AMKL may be treated with different methods. Children with DS-AMKL are often treated with low doses of chemotherapy because they experience more side effects. Children with non-DS-AMKL may be treated with a stem cell transplant or with aggressive chemotherapy. Adults with non-DS-AMKL are usually treated with aggressive chemotherapy.

Some types of leukemia are treated with targeted therapy drugs that can recognize specific cells or molecules. Currently, no targeted treatments are available for AMKL.

Chemotherapy

AMKL is often treated with Cytosar-U (cytarabine), VP-16 (etoposide), and anthracycline drugs. Anthracyclines include Cerubidine (daunorubicin), Idamycin (idarubicin), and Novantrone (mitoxantrone).

Doctors usually give chemotherapy in cycles or courses. One cycle may consist of receiving one or more medications and then taking a three- to four-week rest. People with AMKL often receive between four and six cycles of chemotherapy.

Stem Cell Transplantation

If chemotherapy successfully kills most of the leukemia cells, people with AMKL may be able to undergo an allogeneic (donor) stem cell transplant. During this procedure, doctors use radiation and chemotherapy to kill any remaining cancer cells. Then, the person with AMKL receives new stem cells from a healthy donor. The stem cells travel to the bone marrow and begin making new, healthy blood cells. A stem cell transplantation is the only treatment known to lengthen survival for people with AMKL.

Palliative Care

Palliative or supportive care aims to treat symptoms and improve the quality of life for people with a chronic health condition. Palliative care may also help manage the side effects of cancer treatments. People with AMKL may feel more comfortable after receiving palliative treatments such as:

• Medications to treat nausea or vomiting
• Pain medications
• Antibiotics or antifungal drugs that prevent or treat infections
• Transfusions of new red blood cells or platelets
• Nutritional supplements

Prognosis of AMKL

Children with DS-AMKL tend to have a good prognosis. More than 90 percent of children with DS-AMKL will survive.

Adults with non-DS-AMKL often have a poor prognosis. In one study, adults with AMKL lived for an average of six months after being diagnosed. Children with non-DS AMKL also tend to have a poorer outlook. In particular, those with AMKL who have certain gene changes may be more likely to have a worse prognosis.

MyLeukemiaTeam Provides Community

A new cancer diagnosis can be a lot to handle. It may help to have the support of others who understand what you’re going through as you face new challenges. MyLeukemiaTeam is the social network for people with leukemia and their loved ones. More than 7,000 members understand what it’s like to face leukemia, and can provide support and answers.

Are you or a loved one newly diagnosed with acute megakaryoblastic leukemia? Share your experience at MyLeukemiaTeam or comment below to start a conversation.