Accounts for about 14% of leukemias

it is almost exclusively a disease of adults, the peak of presentation being between 40 and 60 years.

CML - The philadelphia chromosome (present in 95% of patients with CML)

• Chromosomes 9 and 22 translocate due to overexpression of tyrosine kinase.
• This results in part of the ABL proto-oncogene from chromosome 9 being fused with the BCR gene from chromosome 22. The resulting BCR-ABL gene codes for a fusion protein that has tyrosine kinase activity in excess of normal.

Chronic myeloid leukaemia has three typical phases: the chronic phase, the accelerated phase and the blast phase.

The chronic phase can last around 5 years, is often asymptomatic and patients are diagnosed incidentally with a raised white cell count.

The accelerated phase occurs where the abnormal blast cells take up a high proportion of the cells in the bone marrow and blood (10-20%). In the accelerated phase patients become more symptomatic, develop anaemia and thrombocytopenia and become immunocompromised.

The blast phase follows the accelerated phase and involves an even high proportion of blast cells and blood (>30%). This phase has severe symptoms and pancytopenia. It is often fatal.

Presentation

(60-70 years)

• anaemia: lethargy
• weight loss and sweating are common
• splenomegaly may be marked → abdo discomfort
• an increase in granulocytes at different stages of maturation +/- thrombocytosis
• decreased leukocyte alkaline phosphatase