Acute megakaryoblastic leukemia

Synonyms

1

Overview

Acute megacaryoblastic leukemia (AMKL) is a rare form of malignant bone marrow cancer involving the proliferation of immature precursors of blood cells. More specifically, it involves the rapid proliferation of megakaryoblasts (premature form of megakaryocytes).

It is classified under M7 in the French-American-British classification.

Symptoms

  • Asthenia
  • Nausea
  • Vomiting
  • Photophobia
  • Cranial nerve palsies
  • Pallor
  • Fever
  • Dizziness
  • Respiratory symptoms
  • Easy bruising
  • Excessive bleeding
  • Coagulation disorders
  • Neurological disorders
  • Enlarged gums
  • Fatigue
  • Palpitations
  • Bone pain
  • Abdominal pain
  • Headache
  • Increased risk of infection
  • Chest pain
  • Shortness of breath
  • Urination pain
  • Enlarged liver
  •  Enlarged spleen
  • Weight loss

Causes

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

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 (MPO) 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

Complete remission and long-term survival are more common in children than adults. Prognosis depends upon the 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. The last third of cases may be heterogeneous, and carry a poor prognosis.