The bone marrow, a spongy tissue inside bones, functions as a factory for producing blood cells. It is responsible for creating red blood cells that carry oxygen, white blood cells that fight infection, and platelets that help with clotting. When this production system is disrupted, it can lead to a range of health issues.
Decoding Myelodysplastic Syndromes (MDS)
Myelodysplastic syndromes (MDS) are a group of cancers where the bone marrow fails to produce enough healthy, mature blood cells. This condition stems from a disorder in the hematopoietic stem cells, which are the foundational cells that should develop into all types of blood cells. Instead of maturing properly, the cells in the marrow can be abnormal in appearance, a condition known as dysplasia. MDS is most commonly diagnosed in older adults, with the typical age of onset around 70 years.
The failure to create functional cells leads to low blood counts, referred to as cytopenias. This can manifest as anemia (a shortage of red blood cells), causing fatigue; neutropenia (a lack of certain white blood cells), increasing susceptibility to infections; or thrombocytopenia (a low platelet count), leading to easy bruising. While some individuals experience these symptoms, about half of patients are asymptomatic at first, with the condition discovered through routine blood tests.
There are several different subtypes of MDS, which are classified based on specific characteristics of the blood and bone marrow cells. The core issue across all subtypes is the bone marrow’s inability to maintain adequate production of one or more types of blood cells, a process called ineffective hematopoiesis.
The Transformation Pathway: From MDS to Acute Myeloid Leukemia (AML)
A significant concern for individuals diagnosed with MDS is the potential for the disease to progress into acute myeloid leukemia (AML), a transformation that occurs in about 30% of patients. When AML develops from MDS, it is often called secondary AML (sAML). This form of AML is characterized by the rapid and uncontrolled growth of abnormal, immature white blood cells known as myeloblasts.
The transition from MDS to AML is driven by the accumulation of additional genetic mutations within the abnormal bone marrow stem cells. These genetic changes accelerate the disease process, leading to a more aggressive state where leukemic cells overtake the bone marrow. This results in an increase in the percentage of blast cells in the bone marrow and bloodstream.
The risk of this progression is not uniform for all patients with MDS. It varies depending on the specific subtype of MDS and the particular chromosomal abnormalities present. Scoring systems, such as the International Prognostic Scoring System (IPSS), are used to assess this risk by evaluating factors like blood cell counts and genetic markers. This helps in predicting the likelihood of transformation and guiding management.
Recognizing the Shift: Symptoms and Diagnostic Confirmation
The progression from MDS to AML can be signaled by a noticeable worsening of existing symptoms. A person might experience rapidly increasing fatigue, more frequent or severe infections, or unexplained bruising and bleeding that is more pronounced than before. New symptoms can also emerge, such as persistent fever, unintended weight loss, or pain in the bones.
To confirm the transformation, healthcare providers rely on specific diagnostic tests. A complete blood count (CBC) with a differential is a primary tool, as it can reveal marked changes in blood cell numbers and an increase in the percentage of blast cells. While blood tests are indicative, a bone marrow aspiration and biopsy is the definitive procedure for diagnosis.
This biopsy allows for a direct examination of the bone marrow, where a pathologist assesses cell morphology and calculates the percentage of blast cells. A diagnosis of AML is confirmed when blast cells make up 20% or more of the cells in the bone marrow or blood. Further tests, like cytogenetic analysis and molecular testing, identify specific chromosomal abnormalities and gene mutations that influence prognosis and treatment decisions.
Navigating Treatment for AML Evolved from MDS
Treating AML that has developed from MDS, known as secondary AML, often presents unique challenges. This form of leukemia is frequently considered more difficult to treat and may be associated with a different prognosis compared to de novo AML. The primary goals of treatment are to achieve a complete remission, manage symptoms, and maintain the patient’s quality of life.
Treatment decisions are highly individualized, factoring in the patient’s age, overall health, and the specific genetic features of the leukemia cells. For younger and healthier patients, intensive chemotherapy might be an option. For older adults or those with other health issues, less intensive approaches are often used, such as hypomethylating agents like azacitidine or decitabine, which may have already been used to manage the preceding MDS.
In cases where specific genetic mutations are identified, targeted therapy drugs may be employed. For suitable patients, an allogeneic stem cell transplant, also known as a bone marrow transplant, offers a potential path to a cure. This procedure involves replacing the patient’s diseased bone marrow with healthy blood-forming stem cells from a donor.
Throughout any treatment regimen, supportive care is a component. This includes blood and platelet transfusions to manage low counts, as well as antibiotics to prevent or treat infections that can arise from a weakened immune system. Prognostic factors such as specific cytogenetic abnormalities and the patient’s age are considered when formulating a comprehensive treatment plan.