Acute Megakaryoblastic Leukemia

What is Acute Megakaryoblastic Leukemia?

Acute megacaryoblastic leukemia is characterized by the presence in the bone marrow and blood of megakaryoblasts – cells with a hyperchromic (highly stained) nucleus, narrow cytoplasm with filamentous outgrowths, and undifferentiated blasts. Ugly megakaryocytes and fragments of their nuclei are often found in the blood and bone marrow. Acute megakaryoblastic leukemia is the most common type of acute leukemia in children with trisomy 21 (Down syndrome).

Often megakaryoblastic leukemia is combined with bone marrow fibrosis (acute myelosclerosis). Poor in treatment, therefore, the prognosis is usually unfavorable.

Pathogenesis during Acute Megakaryoblastic Leukemia

When studying megakaryoblasts by electron microscopy using cytochemical staining for myeloperoxidase, a specific enzyme location was found in them (Breton – Gorius). The above technique is used to identify megakaryoblasts. The megakaryoblastic nature of the cells is determined not only by electron microscopy in combination with a cytochemical study for peroxidase, but also with the help of anti-platelet antisera that detect specific markers on the cells of this series.

With this form, ugly megakaryocytes, fragments of their nuclei and accumulations of platelets are often found in the blood and bone marrow. The platelet level in the blood, as a rule, exceeds the norm.

Symptoms of Acute Megakaryoblastic Leukemia

The clinical picture of acute megakaryoblastic leukemia is for the most part devoid of specific features. In the outcome of the disease, suppression of normal sprouts of myelopoiesis and other signs of the terminal stage are observed. In some cases, acute megakaryoblastic leukemia may have a clinical and hematological picture of acute low-percentage leukemia, and, according to bone marrow histology, a picture of myelofibrosis. This form of megakaryoblastic leukemia is characterized by a low percentage of blast cells in the bone marrow and blood, polymorphic-cellular composition of the bone marrow, often expressed megakaryocytosis in the bone marrow, and diffuse myelofibrosis, sometimes osteomyelosclerosis. Myelofibrosis, as a rule, does not allow bone marrow puncture to be obtained throughout the illness. The cytological and cytochemical analysis of blast cells entering the blood, for the most part, does not reveal specific signs in them of belonging to any germ of hematopoiesis.

This form of acute leukemia is difficult to distinguish from subleukemic myelosis with cytopenia and the early appearance of blast cells in bone marrow and blood.

Myelofibrosis and a low content of rarely dividing blasts complicate the cytostatic therapy necessary due to deep cytopenia. In most cases, cytostatic therapy does not give a good effect and even exacerbates cytopenia. The most effective treatment for acute megakaryoblastic leukemia with severe myelofibrosis is a bone marrow transplant.