It's important to know if someone has Philadelphia positive ALL (Ph+ ALL) because it affects which treatments are likely to work best. The Philadelphia chromosome (Ph) is the result of a genetic change in the leukaemia cells. And it's found in about 1 in 4 (25%) adults with ALL. It is less common in children and younger people and more common in older people who have ALL. The genetic change in the cells occurs by accident during the person's lifetime. So, the Philadelphia chromosome isn't inherited and can't be passed on to children.

The Philadelphia chromosome is found when a particular change has happened in the chromosomes of the leukaemia cells. Every cell in the body has 23 pairs of chromosomes. They are numbered 1 to 22, (the 23rd pair are the sex chromosomes XY for males and XX for females).

In Philadelphia positive leukaemia a bit from chromosome 9 and a bit from chromosome 22 have broken off and swapped places. This is called a translocation. The Philadelphia chromosome is sometimes written as t(9;22) the t standing for translocation.

Chromosomes are made up of millions of genes. These genes control day to day activities inside the cells. The translocation in the Ph chromosome causes two genes that are normally separated, to join together making a new gene called the BCR-ABL gene.  This gene makes a special protein (BCR-ABL tyrosine kinase), which stimulates the leukaemia cells to grow and divide.

Ph+ALL has a higher risk of coming back after treatment than some other types of ALL. So, more intensive chemotherapy and a stem cell transplant may be offered to your aunt, if she is fit enough to cope with this. A newer treatment, imatinib (Glivec®), that targets the protein made by the Ph+ leukaemia cells may also be used.

Reference

• Gleissner B et al. Leading prognostic relevance of the BCR-ABL translocation in adult acute B-lineage lymphoblastic leukemia: a prospective study of the German Multicenter Trial Group and confirmed polymerase chain reaction analysis. Blood 2002 Mar 1;99(5):1536-43