Chronic myeloid leukaemia (CML)

Classification according to ICCC: I.c (Chronic myeloproliferative diseases)

Definition

Chronic myeloid leukaemia (CML) is a malignant clonal disorder of pluripotent stem cells. The failure of proliferation control is linked to the presence of Philadelphia chromosome (Ph chromosome), which is a chromosomal abnormality resulting from a reciprocal translocation between chromosome 9 and chromosome 22, designated as t(9;22). This aberration leads to a fusion gene bcr/abl which is present in all hematopoietic cells and has a tyrosinkinase activity.

Occurrence

Chronic myeloid leukaemia (CML) accounts for 2 to 5 percent of childhood leukaemias, and is rare in children.

Symptoms

Symptoms of chronic myeloid leukaemia are non-specific. Anaemic syndrome, fatigue, or weight loss are rarely present.

Diagnosis

Diagnosis is based on the findings in blood count: leucocytosis, WBC differential usually shows granulocytes in all stages of maturation, from blasts to mature, morphologically normal granulocytes. The numbers of Auer rods, metamyelocytes, myelocytes and neutrophil segments are relatively small, and basophilia is often apparent. Thrombocytopenia is rather exceptional. CML is also characterised by a distinct splenomegaly. Diagnosis is made up of the examination of bone marrow aspiration and biopsy, which is not entirely pathognomonic, of cytogenetic examination and molecular genetic examination of bone marrow material, which indicates the presence of bcr/abl gene.

Classification

Staging in chronic myeloid leukaemia (CML) is described in three phases: chronic phase, accelerated phase, and blast phase.

Therapy

Treatment is initiated with tyrosin kinase inhibitors (imatinib, dasatinib); after achieving the molecular genetic remission (major response), all paediatric patients are treated with an allogeneic transplantation of stem cells.

Treatment outcomes

Disease prognosis depends on the existence of a HLA-identical donor and on managing treatment complications – the toxicity of allogeneic transplantation of stem cells. In general, the prognosis is good.

Role of general paediatrician

The general paediatrician plays an important role in the diagnostic process, as the clinical presentation is rather poor. The paediatrician subsequently cooperates with the haematological centre during the period of treatment with tyrosine kinase inhibitors, which lasts several months and is performed on an outpatient basis.