Sickle-cell Anemia: Pathogenesis, Clinical features and its Investigation

Sickle-cell Anemia: Pathogenesis, Clinical features and its Investigation

Microscopic view of sickle shaped RBC’s


It is a genetic disorder of RBC in which the normal disc shape of RBC changes to crescent shape therefore termed as sickle cell. It is a type of haemoglobinopathy having abnormal hemoglobin, hemoglobin S. The abnormality is in the form of alteration in the amino acid structure of the polypeptide chains of globins fraction of hemoglobin.

It is a genetic disease, inherited from parents to offspring. it is caused by autosomal recessive single gene defect in beta chain of hemoglobin, which results in production of sickle cell hemoglobin (Hbs). When person inherits 2 abnormal genes from both the parents sickle cell disease occurs, but if the person inherits one single abnormal gene from one of the parent he is said to have sickle cell trait or carriers. The person with sickle cell trait are resistant to falciparum malaria in early childhood. However patients with sickle cell anemia do not have greater resistance to falciparum malaria.

Pathogenesis-

Image showing blockage of arteries from sickle shaped RBC’s


Normal RBC’s have elasticity, so that they can change their shape and size while passing through capillaries. But in sickle cell disease, the cells become sticky and rigid; elasticity is decreased due to low oxygen tension. As the result of the rigidity, cell wall does not allow the cell to change its shape and size during passing through narrow capillaries. This causes cells to get trapped in small vessels, thereby blocking them. This results in vessels occlusion and ischemia. Sickle cells increases the viscosity of blood, they obstruct the blood flow, forms thrombus and causes tissue infarction. This causes severe pain, swelling and tenderness called as crises.
These deformed Sickled cells are largely phagocytozed, thereby reducing the life spasm of cells and giving rise to hemolysis.
Normal RBC’s have 90-120 days of life span, but in sickle cell due to their abnormal shape, there is large destruction of RBC i.e., cells have life span of 10-20 days. This results in severe hemolytic anemia; however bone marrow tries to compensate by producing new cells.

Clinical Features-

The disease usually starts at the young age of 4-5 months. Clinical features depend on the severity of diseases. The features are due to either hemolysis in the form of anemia or due to vessel occlusion in the form of pain, swelling, (hands and feet) tenderness, stroke etc. patients are prone to infections.
The disease manifests in the form of various types of crises like Infarction crises, Aplastic crises, Hemolytic crises, Splenic sequestration crises.
Sickle cell trait patients are usually clinically well with normal blood counts are very less or no symptoms.

Common features seen in sickle cell anemia are: 

  • Fatigue
  • Irritability
  • Anemia
  • Jaundice
  • Pain and edema in hands and feet
  • Pain in chest, back, arms and legs
  • Recurrent infections

Investigations

1. CBC
  • Hb%- 6-8g/dl
  • Raised Reticulocyte count
  • Blood smear- sickle celled RBC’s
  • Hemoglobin electrophoresis
2. Urine analysis
3. Chest X-Ray

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