Myeloid disorders are a diverse group of conditions affecting the bone marrow, the spongy tissue inside your bones responsible for producing blood cells. These disorders occur when the bone marrow produces an imbalance in the number or function of healthy blood cells. This article explores myeloid disorders, their symptoms, diagnosis, and treatment approaches.
Understanding Myeloid Disorders
Myeloid cells are a broad category of blood cells originating from myeloid progenitor cells in the bone marrow. This lineage includes red blood cells, which transport oxygen, and platelets, which help with blood clotting. Myeloid cells also encompass various types of white blood cells, such as neutrophils, eosinophils, basophils, and monocytes, which are integral components of the immune system, defending against infections.
Myeloid disorders arise when the bone marrow’s production of these cells goes awry. This can manifest as overproduction, underproduction, or the production of abnormal, dysfunctional cells. These issues stem from genetic changes in the blood-forming stem cells within the bone marrow, which are acquired rather than inherited.
The main categories of myeloid disorders include myeloproliferative neoplasms (MPNs), myelodysplastic syndromes (MDS), and acute myeloid leukemia (AML). MPNs involve the overproduction of mature myeloid cells, such as in polycythemia vera (too many red blood cells) or essential thrombocythemia (too many platelets). Myelodysplastic syndromes are characterized by ineffective blood cell production, where the bone marrow produces immature or defective cells, leading to low blood cell counts. Acute myeloid leukemia, a more aggressive form, involves the rapid production of immature white blood cells (blasts) that do not function correctly and crowd out healthy blood cells.
Recognizing Potential Signs
Symptoms of myeloid disorders vary depending on the affected blood cell type and imbalance severity. Fatigue and weakness are common signs, often resulting from anemia, where there are not enough healthy red blood cells to carry oxygen. Individuals might also experience shortness of breath or paleness due to reduced oxygen delivery.
Problems with white blood cells can lead to increased susceptibility to infections, manifesting as frequent fevers, chills, or recurrent illnesses. When platelet counts are low or dysfunctional, individuals may notice easy bruising, nosebleeds, or prolonged bleeding from minor cuts. Conversely, an excess of platelets, as seen in some MPNs, can also lead to abnormal clotting or, less commonly, bleeding.
Other general symptoms can include unexplained weight loss, night sweats, or an enlarged spleen, which might cause abdominal discomfort or a feeling of fullness. These symptoms are not exclusive to myeloid disorders and warrant medical evaluation to determine the underlying cause. Risk factors for developing myeloid disorders include increasing age and prior exposure to certain chemotherapy drugs or radiation therapy.
How Myeloid Disorders Are Diagnosed
Diagnosing myeloid disorders begins with a comprehensive evaluation of a person’s blood. A complete blood count (CBC) is a standard initial test that measures red blood cells, white blood cells, and platelets, indicating abnormalities in their counts. If CBC results suggest a myeloid disorder, further specialized tests are performed.
A bone marrow biopsy and aspiration are done to obtain samples for examination. During this procedure, liquid bone marrow (aspiration) and a piece of solid bone marrow (biopsy) are collected from the hip bone. These samples are then analyzed under a microscope to assess cellularity, presence of abnormal cells, and the marrow’s overall structure.
Genetic testing plays an important role in diagnosis and classification. Cytogenetic analysis examines chromosomes within bone marrow cells for large-scale genetic abnormalities. Molecular testing looks for specific gene mutations, such as JAK2, CALR, or MPL mutations found in myeloproliferative neoplasms, or other mutations relevant to myelodysplastic syndromes or acute myeloid leukemia. Identifying these genetic changes helps confirm the diagnosis, classify the specific type of myeloid disorder, and provides information about disease behavior.
Treatment Approaches
Treatment for myeloid disorders is individualized, depending on the specific type of disorder, its stage, the patient’s age, overall health, and the presence of genetic mutations. Goals of treatment range from managing symptoms and improving quality of life to slowing disease progression, achieving remission, or aiming for a cure.
For some slow-growing myeloid disorders, particularly certain myelodysplastic syndromes or myeloproliferative neoplasms, a “watch and wait” approach might be adopted, with regular monitoring of blood counts and symptoms. When intervention is needed, chemotherapy is a treatment using drugs to kill rapidly dividing abnormal cells. Targeted therapies, which focus on specific molecular pathways or mutations driving the disease, are available for certain myeloid disorders, such as drugs that inhibit the JAK2 pathway.
Immunotherapy, which harnesses the body’s immune system to fight cancer cells, is another treatment option. Stem cell transplantation, also known as bone marrow transplantation, can cure some myeloid disorders, particularly for younger patients with high-risk disease. This procedure involves replacing the patient’s unhealthy bone marrow with healthy blood-forming stem cells from a donor.
Supportive care measures are an important part of managing myeloid disorders, aiming to alleviate symptoms and complications. This can include blood transfusions for anemia or low platelet counts, growth factors to stimulate blood cell production, and antibiotics to prevent or treat infections. The treatment plan is a collaborative decision between the patient and their healthcare team, adjusted to the disease’s response and the patient’s needs.