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Myelodysplastic Syndrome (MDS)

  1. The myelodysplasia are clonal disorders characterized clinically and morphologically by defective and ineffective hematopoiesis.
  2. They are the result of pathology in the hematopoietic stem cells and are thus characterized by cytopenia of varying degree in red cell, white cell, and megakaryocytic lines.
  3. All have a tendency to terminate in AML.
  4. Chromosomal abnormalities loss of chromosome 5 (13%) and chromosome 7 (5%), trisomy 8 (5%), and deletions of parts of chromosomes 17 and 20. 
WHO classification of Myelodysplastic syndromes
  1. Refractory anaemia (RA)                                                                                              
  2. Refractory anemia with sideroblasts (RARS)                                              
  3. Refractory cytopenias with multilineage dysplasia (RCMD)                              
  4. Refractory anaemia with excess blasts (RAEB)                                         
  5. Myelodysplastic syndrome with 5q
  6. Myelodysplastic syndrome unclassified
Bone Marrow Findings
  1. Blasts < 5%, Erythroid dysplasia only
  2. Blasts < 5%, Ringed sideroblasts >15%
  3. Blasts <5%, 2 – 3 lineage dysplasia  
  4. Blast 5 – 20%, 2 – 3 lineage dysplasia
  5. Myelodysplastic syndrome associated with a del (5q) cytogenetic abnormality, Blasts < 5%Often normal or increased blood platelet count
  6. None of the above or inadequate material
  1. RA                                  
  2. RARS                                 
  3. RAEB                 
  4. RAEB + (Transformation)                               
  5. Ch myelomonocytic level
Extra Edge: 

Causes of MDS, 1. Radiation   2. Benzene exposure 3. Late toxicity of Busulphan, nitrosurea, Procarbazine, Topoisomerase inhibitor.


Cytogenetic Abnormalities in MDS: Facts to Remember
  1. Monosomy 7 is the most frequent cytogenetic abnormality in children. 
  2. Deletion 5q (5q-) is the most frequent cytogenetic abnormality in adults.
  3. Trisomy 8 is the most frequent trisomy.
Clinical features of the myelodysplasia all relate to bone marrow failure.
  1. MDS particularly affects the elderly (chronic myelomonocytic leukemia can occur in children)
  2. Anemia features (progressive fatigue, dyspnea on exertion, pallor);
  3. Neutropenia features (frequent infections);
  4. Thrombocytopenia features (bleeding and bruising).
  5. Splenomegaly in 20% cases
  1. Laboratory findings include cytopenia, with anemia being the most frequent presenting feature.
  2. Peripheral smear demonstrates (teardrop forms, Pelger Huët, hypogranulated, hypo lobular WBC forms, and abnormal platelet forms).
  3. Bone marrow shows morphologic abnormalities including megaloblastic RBC, asynchronous maturation of cytoplasm and nuclei, ringed sideroblast forms, micromegakaryocytes, and excess blast forms.
  4. In MDS – BM is hypercellular & normo cellular mainly but in 20% of cases it may be hypocellular.
MCQ: Essentials of Diagnosis
  1. Cytopenias with a hypercellular bone marrow.
  2. Morphologic abnormalities in two or more hematopoietic cell lines.
  1. Supportive therapy: Erythropoietin (EPO) and G-CSF.
  2. New agents             
    (a) Lenalidomide an immunomodularly agent,
    (b) Azacytidine, an antimetabolite that impairs DNA methylation.
  3. BMT
Prognosis is variable. Most MDS tends to terminate in AML. 
Table - International Prognostic Scoring System
  Score Value
Prognostic Variable 0 0.5 1.0 1.5 2.0
Bone marrow blasts (%) <5% 5–10%   11–20% 21–30%
Karyotype Good Intermediate Poor    
Cytopenia (lineages affected)  0 or 1 2 or 3      

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