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Sideroblastic anemias

Pathophysiology. of sideroblastic anemia
  1. Caused by disorder in the synthesis of the heme moiety of hemoglobin are characterized trapped iron in the mitochondria of nucleated RBC.
  2. Most of the enzymes for protoporphyrin synthesis are located in the nucleated RBC mitochondria.
  3. Derangements in these pathways cause iron accumulation in the perinuclear mitochondria, which renders this anemia its characteristic morphologic finding of ringed sider-oblasts.
  4. RBC Population is hypochromic and microcytic. It leads to ineffective erythropoiesis
  5. Defect:  There is defect in incorporating Fe into Hb within RBC
  6. P/s. microcytic hypochromic or dimorphic.
Important Points: 
  1. a. Sideroblast   - Erythroblast with Prussian blue positive iron granules in cytoplasm.
  2. b. Siderocytes   - Mature RBC with Prussian blue positive iron granules in cytoplasm.
    - Granules also positive for iron with Romanovsky dye
    - Granules appears as basophilic granules called as Pappenheimer bodies.
  3. Ring Sideroblast – Sideroblast in which iron granules forms partial / complete ring around nucleus
    (Ring is made up of mitochondria with iron granules).
Causes of Sideroblastic Anemia
  1. Hereditary
    1. X-linked                    
    2. Mitochondrial                  
    3. ​Autosomal dominant
  2. Acquired       
    1. Primary : MDS                              
    2. Secondary
  1. Hematological:      
    1). Myelofibrosis                            
    2). Polycythemia vera        
    3). Acute leukemia             
    4). Myeloma                                        
    5). Lymphoma                      
    6). Hemolytic anemia
  2. Other Diseases:   
    1). Rheumatoid arthritis              
    2). Myxoedema
Drugs chemicals and toxins
1). Isoniazid, Penicillamine                
2). Alcohol     pyridoxine deficiency                
3). Lead poisoning.


Important Points:
Pearson syndrome occurs in congenital sideroblastic anemia, there is pancytopenia with macrocytosis.
Laboratory findings of sideroblastic anemia
  1. Increased ferritin levels                    
  2. Normal decreases total iron-binding capacity
  3. Hematocrit of about 20-30%                    
  4. Serum Iron: High
  5. High transferrin saturation                    
  6. The mean corpuscular volume or MCV is usually normal or low
  7. Stainable BM hemosiderin is increased.
  1. Older than 60 years levels of 8-10 g/dl. 
  2. Normocytic or even macrocytic and dimorphous population with some very small cell.
  3. Iron staining demonstrates the ringed sideroblasts.
  4. Iron studies show elevated ferritin levels and high serum iron levels with high transferrin saturation.
  1. Pyridoxine in high does; however, in all but the hereditary cases, this usually fails.
  2. Often, these patients have transfusion depended diseases.
  3. Exogenous erythropoietin.
Important Points:
Lab Parameter IDA Thalassemia Sideroblastic AOCD
S. Fe N N
TIBC N N or ↓
% saturates (30-50%) ↓↓ N↑ N or ↑ ↓ (10-20)
S ferritin <15 ↑ (50-300) ↑(50-300) N or ↑
Hb electrophoresis N Abnormal N N
Free erythrocyte protoporphyrin N

* AOCD – Anemia Of Chronic Disease.

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