Blast phase

The blast phase is a pivotal stage in the progression of chronic myelogenous leukemia (CML). Distinguished by a marked increase in immature and abnormal white blood cells within the bone marrow and the circulatory system, this phase underscores the severity and advancement of the disease. It is colloquially and medically known as the blast crisis.

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CML Accelerated Phase

LMC4

Schematic of the Philadelphia Chromosome

Definition and Overview

Chronic myelogenous leukemia (CML) is a specific type of cancer that starts in the blood-forming cells of the bone marrow and progressively invades the bloodstream. This malignancy typically evolves through three main phases: the chronic phase, the accelerated phase, and the blast phase. Among these, the blast phase is recognized as the most severe and aggressive stage.

Characteristics of Blast Phase

The blast phase is hallmarked by the abundant presence of "blast" cells. These cells are immature variations of white blood cells, which due to their abnormality, pose a threat to the effective functioning of the body's immune system.

Diagnostic Indicators

For a patient to be diagnosed as being in the blast phase of CML, medical practitioners typically rely on the following criteria:

• A composition of 20% or more blast cells in the peripheral blood or bone marrow samples.
• Elevated levels of specific enzymes, most notably lactate dehydrogenase (LDH). A high LDH level typically indicates accelerated cell death and regeneration.
• Manifestation of symptoms that resonate with severe leukemia, such as extreme fatigue, inexplicable weight loss, and an enlarged spleen.

Associated Complications

The blast phase is indicative of a malfunctioning bone marrow due to the overpopulation of abnormal white blood cells. This overpopulation can result in:

• Anemia: Resulting from a significant reduction in red blood cells, causing symptoms like fatigue and general weakness.
• A heightened vulnerability to infections: Caused by the diminished count of healthy white blood cells that are integral to the body's defense mechanism.
• Bleeding disorders: Owing to a reduction in platelets, which play a crucial role in the clotting process.

Treatment Approaches

Given the severity of the blast phase, timely and aggressive intervention becomes crucial. Potential treatments encompass:

• Chemotherapy: A procedure aimed at annihilating cancer cells and inhibiting their uncontrolled proliferation.
• Stem cell transplantation: This involves substituting the patient's compromised bone marrow with a healthy one from a suitable donor.
• Targeted therapies: A more recent advancement, these are drugs designed to specifically target and inhibit molecules that are fundamental to the growth and survival of leukemia cells.

Prognostic Implications

The onset of the blast phase implies a critical progression in CML. Despite the associated challenges, the advancements in medical science, combined with early detection, have ameliorated both the survival rates and the quality of life for affected patients.

See Also

• Leukemia
• Oncology
• Bone marrow biopsy
• Hematopoiesis

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