Which type of leukemia is primarily associated with the Philadelphia chromosome?

Chronic Myelocytic Leukemia (CML) is primarily associated with the Philadelphia chromosome, which is a specific genetic abnormality resulting from a translocation between chromosomes 9 and 22. This genetic alteration leads to the formation of the BCR-ABL fusion protein, which has tyrosine kinase activity that promotes cell proliferation and inhibits apoptosis, resulting in the excessive accumulation of myeloid cells in the bone marrow and peripheral blood.

CML typically progresses through phases, starting with a chronic phase where patients may be asymptomatic and later advancing to an accelerated phase and then to a blast crisis. The presence of the Philadelphia chromosome is a hallmark of CML and is critical for diagnosis and monitoring the disease, as it also helps guide treatment options including targeted therapies such as tyrosine kinase inhibitors.

While other leukemias may have unique genetic abnormalities, none are as closely associated with the Philadelphia chromosome as CML. Other types of leukemia mentioned do not share this specific chromosomal alteration as a defining feature.