The Philadelphia Chromosome

The Philadelphia Chromosome is a specific genetic abnormality often found in chronic myeloid leukemia (CML), a type of blood cancer. It results from a rare genetic swap where parts of two chromosomes (numbers 9 and 22) break and exchange places. This creates a shortened chromosome called the Philadelphia chromosome, which produces an abnormal protein that promotes uncontrolled cell growth. Detecting this chromosome helps diagnose CML and guides targeted treatments, such as certain medications that specifically block the activity of the abnormal protein. The discovery of the Philadelphia chromosome was a major step in understanding and treating this cancer.