Acute myeloid leukaemia

Acute myeloid leukaemia

Introduction

Acute myeloid leukaemia (AML) is a malignant clonal disorder of haematopoietic progenitor cells. Leukaemic transformation usually occurs at a very early stage of myeloid development, probably at or near the haematopoietic stem cell, but it may develop in a more mature cell. The disease is heterogeneous. The malignant cells acquire genetic alterations which upset their normal mechanisms of self-renewal, proliferation and differentiation. Ultimately the malignant clone causes marrow failure. AML is rare in childhood and the incidence increases with age; two-thirds of cases occur in people aged over 60 years.

Classification

The WHO system has now largely superseded the French-American-British (FAB) classification. The newer classification reduces the bone marrow leukaemic blast cell percentage differentiating AML from myelodysplastic syndrome (see p. 50) from 30% to 20%. Other key changes include the creation of specific subtypes with non-random cytogenetic or equivalent molecular abnormalities, and the distinction of patients with multilineage dysplasia and also previous chemotherapy. The major FAB subtypes are included in the ‘other’ category with the exception of acute promyelocytic leukaemia (previously FAB M3) which is now in the ‘recurrent translocations’ group due to the inevitable presence of t(15;17). It can be seen (Table 20.1) that occasional cases of AML show megakaryocytic or erythroid differentiation. Gene mutations are likely to become increasingly important in classification.

Table 20.1

WHO classification of acute myeloid leukaemia

AML with recurrent genetic abnormalities¹

AML with t(18;21)(q22;q22)

AML with inv (16)(p13;q22) or t(16;16) (p13.1;q22) (M4 Eo)

AML with t(15;17)(q22;q12) (M3:M3V)

AML with t(9;11) (p22;q23)

AML with t(6;9) (p23;q34)

AML with inv(3) (q21;q26.2) or t(3;3) (q21;q26.2)

AML (megakaryoblastic) with t(1;22) (p13;q13)

AML with myelodysplasia-related changes

Therapy related myeloid neoplasms

AML not otherwise specified²

AML with minimal differentiation (M0)

AML without maturation (M1)

AML with maturation (M2)

Acute myelomonocytic leukaemia (M4)

Acute monoblastic/ monocytic leukaemia(M4/5)

Acute erythroid leukaemia (M6)

Acute megakaryoblastic leukaemia (M7)

Acute basophilic leukaemia

Acute panmyelosis with myelofibrosis

Myeloid sarcoma

Myeloid proliferation related to Down syndrome

Blastic plasmacytoid dendritic cell neoplasm

¹ See also Table 2 for genetic changes.

² FAB equivalent is shown in parentheses.

Clinical features

In practice there is little uniformity in presentation. Some patients are remarkably asymptomatic while others are seriously ill. Bone marrow infiltration by leukaemic blast cells usually leads to anaemia, neutropenia and thrombocytopenia. Thus, patients often have symptoms of anaemia, infection and haemorrhage.

One subtype of AML deserves special consideration as it must be treated as a medical emergency:

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Jun 12, 2016 | Posted by admin in HEMATOLOGY | Comments Off

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