Acute Megakaryoblastic Leukemia

Definition

Definition of Acute Megakaryoblastic Leukemia
This leukemia is thought to derive from the transformation of a multipotent myeloid progenitor cell. In the adult patient multilineage dysplasia is a common finding and in some cases a minority of myeloid blast cells is present.

The blast cells show one or more megakaryocytic markers (i.e. Factor VIII, CD61, CD41, or CD42), they test negative when using the anti-myeloperoxidase monoclonal antibody and never show coordinated expression of lymphoid markers, though isolated CD2 or CD7 positivity can be found on some occasions. The CD34, CD13 and CD33 markers are positive in a substantial fraction of cases, as is the case with the CD36/thrombospondin receptor.

Symptoms

Symptoms of Acute Megakaryoblastic Leukemia
In adults include pancytopenia with low blast counts in the blood, myelofibrosis, an absence of lymphadenopathy and hepatosplenomegaly, poor response to chemotherapy,and short clinical course. In children; the same clinical presentation but with variable course especially in very young children; both leukocytosis and organomegaly may be present in children with M7. Complete remission and long term survival are more common in children than adults. In the first three years of life megakaryoblastic leukemia is the most common type of leukemia in patients with Downs syndrome.

Causes

Causes of Acute Megakaryoblastic Leukemia
It is associated with GATA1, and risks are increased in individuals with Down syndrome.
However, not all cases are associated with Down syndrome, and other genes can also be associated with AMKL.
Another related gene is MKL1, which is also known as "MAL". This gene is a cofactor of serum response factor.

Diagnosis

Diagnosis of Acute Megakaryoblastic Leukemia
The morphology of cells was observed by means of bone marrow smear; the immunophenotype was detected by flow cytometry and immunohistochemistry assay.

In blood and bone marrow smears megakaryoblasts are usually medium sized to large cells with a high nuclear-cytoplasmic ratio. Nuclear chromatin is dense and homogeneous. There is scanty, variable basophilic cytoplasm which may be vacuolated. An irregular cytoplasmic border is often noted in some of the megakaryoblasts and occasionally projections resembling budding atypical platelets are present. Megakaryoblasts lack myeloperoxidase activity and stain negatively with Sudan black B. They are alpha naphthyl butyrate esterase negative and manifest variable alpha naphythyl acetate esterase activity usually in scattered clumps or granules in the cytoplasm. PAS staining also varies from negative to focal or granular positivity, to strongly positive staining. A marrow aspirate is difficult to obtain in many cases because of variable degree of myelofibrosis. More precise identification by immunophenotyping or with electron microscopy (EM). Immunophenotyping using MoAb to megakaryocyte restricted antigen (CD41 and CD61) may be diagnostic.

Prognosis

Prognosis of Acute Megakaryoblastic Leukemia
Prognosis depends on cause. One third of cases is associated with a t(1;22)(p13;q13) mutation in children. These cases carry a poor prognosis. Another third of cases is found in Down syndrome. These cases have a reasonably fair prognosis.

Treatment

Treatment of Acute Megakaryoblastic Leukemia
Myeloablative treatment followed, whenever possible, by allogeneic or autologous bone marrow transplant is the treatment of choice.

Prevention

Prevention of Acute Megakaryoblastic Leukemia
Consult with your doctor.