Myelodysplastic Syndromes (MDS)
What are Myelodysplastic Syndromes?
Myelodysplastic Syndromes (MDS) are a group of disorders caused by problems in the bone marrow
that lead to the production of defective or insufficient blood cells. MDS is sometimes referred
to as a “bone marrow failure” condition because it affects the marrow’s ability to produce
healthy blood cells. In MDS, the bone marrow produces abnormal blood cells that are often
ineffective or immature (called blasts). These abnormal cells can crowd out normal blood cells,
leading to shortages of red blood cells, white blood cells, and platelets, increasing the risk
of anaemia, infections, and bleeding.
Key Characteristics of MDS
- Ineffective haematopoiesis: Blood cell production in the bone marrow is disrupted, leading to defective cells that do not mature or function properly.
-
Cytopenias: Low levels of one or more blood cell types:
- Anaemia: Low red blood cells causing fatigue and weakness
- Leukopenia: Low white blood cells increasing infection risk
- Thrombocytopenia: Low platelets causing bruising and bleeding
- Clonal haematopoiesis: MDS arises from a single abnormal stem cell that overproduces defective blood cells.
Types of Myelodysplastic Syndromes
MDS is not a single disease but a group of related disorders. Classification depends on blast percentage, affected blood cell lines, and chromosomal abnormalities. Common subtypes include:
- Refractory Anaemia (RA): Low red blood cell counts with ineffective erythropoiesis.
- Refractory Cytopenia with Multilineage Dysplasia (RCMD): Dysfunction across multiple blood cell lines.
- Refractory Anaemia with Ringed Sideroblasts (RARS): Presence of ringed sideroblasts—abnormal red cell precursors with iron accumulation.
- Chronic Myelomonocytic Leukaemia (CMML): MDS with features of CML and increased monocytes.
- MDS with Excess Blasts: Increased blasts with higher risk of progression to acute myeloid leukaemia (AML).
- MDS with Isolated Deletion of 5q: Loss of part of chromosome 5; often better prognosis and specific treatment options.
Symptoms of MDS
- Fatigue or weakness (anaemia)
- Paleness due to low red blood cells
- Frequent infections or fever
- Easy bruising, nosebleeds, or bleeding gums
- Shortness of breath
- Pale or splotchy skin
- Enlarged spleen or liver in some cases
Diagnosis of MDS
- Blood tests (CBC): Abnormal red cell, white cell, and platelet counts; peripheral smear may show blasts or abnormal cell shapes.
- Bone marrow biopsy: Primary diagnostic test assessing dysplasia, blast count, and overall marrow quality; ringed sideroblasts may be seen.
- Cytogenetic testing: Detects chromosomal abnormalities (e.g., 5q or 7 deletions) to guide prognosis.
- Molecular testing: Identifies gene mutations that inform risk and therapy.
Treatment of MDS
Treatment aims to manage symptoms, improve blood counts, and slow disease progression. Options depend on disease severity, patient age, and overall health.
- Supportive care: Blood transfusions, growth factors (e.g., erythropoiesis-stimulating agents), antibiotics or antifungals for infections.
- Chemotherapy: Hypomethylating agents such as azacytidine or decitabine for higher-risk disease; intensive chemotherapy if progression to AML occurs.
- Stem cell transplant: The only potential curative option, mainly for high-risk or progressive disease.
- Immunosuppressive therapy: Agents such as antithymocyte globulin (ATG) in selected cases.
- Targeted therapy: Lenalidomide for MDS with isolated 5q deletion.
- Clinical trials: Important option for high-risk or treatment-resistant MDS.
Prognosis
- Depends on age, cytogenetics, blast percentage, and number of cytopenias
- Risk scoring systems (e.g., IPSS) help predict progression to AML
- Response to therapy or stem cell transplant can significantly extend survival
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