Acute Myeloid Leukemia (AML) is a cancer that affects the blood and bone marrow. It is characterized by the rapid, uncontrolled growth of abnormal blood cells. This condition interferes with the bone marrow’s ability to produce healthy, functional blood cells. AML is an acute leukemia because it progresses quickly and requires immediate attention.
Healthy Blood Production
The human body constantly produces new blood cells through a process called hematopoiesis, which occurs in the bone marrow. Bone marrow is the soft tissue found inside certain bones, serving as the factory for all blood components.
Hematopoietic stem cells (HSCs) reside within the bone marrow and are the foundational cells for all blood cell types. These multipotent cells possess the ability to both self-renew and differentiate into specialized cell lineages. This differentiation process leads to the formation of myeloid progenitor cells and lymphoid progenitor cells.
Myeloid progenitor cells further mature into red blood cells that carry oxygen, and platelets involved in blood clotting. They also develop into several types of white blood cells, including neutrophils, monocytes, eosinophils, and basophils, each playing a role in the body’s immune defense. Lymphoid progenitor cells, in contrast, give rise to lymphocytes, another type of white blood cell for specific immunity.
This hierarchy ensures a continuous supply of diverse blood cells, each performing specific tasks for overall health. The bone marrow’s ability to regulate this production is important for bodily function.
The Genesis of AML
Acute Myeloid Leukemia originates from genetic alterations in the DNA of hematopoietic stem cells or early myeloid progenitor cells in the bone marrow. These mutations disrupt the regulatory mechanisms governing cell growth, maturation, and programmed cell death.
The genetic changes lead to the uncontrolled proliferation of immature cells known as “blasts.” Instead of developing into mature blood cells, these blast cells remain in an undifferentiated state, accumulating rapidly within the bone marrow. This accumulation is a hallmark of AML, distinguishing it from other blood disorders.
Various genetic mutations can contribute to AML development. For example, chromosomal translocations, where chromosome parts break off and rejoin incorrectly, can create fusion genes that interfere with normal cell processes. Mutations in genes like NPM1, FLT3, RUNX1, and CEBPA are frequently observed in AML patients.
These genetic changes often promote the self-renewal of abnormal stem cells and the proliferation of progenitor cells. The consequence is a block in differentiation, meaning the cells fail to mature into their intended forms. The combination of mutations can influence the subtype of AML and its behavior.
The accumulation of these immature blast cells signifies a breakdown in the process of hematopoiesis. The bone marrow, instead of producing healthy blood cells, becomes dominated by these non-functional cells.
Consequences of Abnormal Cell Growth
The uncontrolled accumulation of abnormal blast cells in the bone marrow has effects on the body’s ability to produce healthy blood cells. These leukemic blasts crowd out the space occupied by developing red blood cells, platelets, and mature white blood cells. This displacement leads to a reduction in the production of healthy blood cells, a condition called bone marrow failure.
The deficiency of red blood cells, called anemia, is a common consequence. With fewer red blood cells transporting oxygen, individuals often experience symptoms such as fatigue, weakness, and shortness of breath. Pale skin can also be observed due to the reduced oxygen-carrying capacity of the blood.
A decrease in the number of platelets, called thrombocytopenia, impairs the blood’s ability to clot. This can manifest as easy bruising, frequent nosebleeds, or bleeding from the gums. Petechiae, which are tiny red or purple spots on the skin from minor bleeding under the surface, may also appear.
The bone marrow’s inability to produce mature white blood cells, especially neutrophils (neutropenia), leaves the body vulnerable to infections. Patients with AML often experience recurrent infections, which can be severe and accompanied by fever. Even if the overall white blood cell count appears high, these are primarily non-functional blast cells that cannot fight pathogens.
Sometimes, the abnormal blast cells can spread beyond the bone marrow and infiltrate other organs, such as the spleen, liver, or lymph nodes, leading to enlargement. While less common, infiltration of the central nervous system can lead to headaches, vision problems, or seizures.