VII. TEACHING POINTS

1. There are many causes of macrocytic anemia. They are commonly divided into two categories: megaloblastic and non-megaloblastic.
   
   
2. Megaloblastic anemias are due to vitamin B12 or folic acid deficiency and are characterized by dissociation between nuclear and cytoplasmic maturation of hematopoietic cells (immature nuclei due to abnormal DNA synthesis with mature cytoplasmic organelles).
   
   
3. There are many causes of B12 and folic acid deficiency. Pernicious anemia is a specific type of B12 deficiency that is due to lack of intrinsic factor production by the gastric parietal cells.
   
   
4. MDS is a clonal stem cell abnormality with two different mechanisms for producing cytopenia: increased apoptosis of precursor cells and abnormal proliferation and maturation of the abnormal stem cells.
   
   
5. Macrocytosis is common in patients with MDS, but not universal.
   
   
6. There are subtypes of MDS and individual prognostic factors that can be used to establish an individual patient’s risk of transformation to acute myeloid leukemia.
   
   
7. There is no standard therapy for MDS. It is important for patients who have good performance status to be considered for clinical trials.

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