What is sickle cell anemia?


Sickle cell anemia is an inherited form of anemia — a condition in which there is enough healthy red blood cells to carry adequate oxygen throughout the body. It affects hemoglobin, the molecule in red blood cells that delivers oxygen to cells throughout the body. People with this disorder have atypical hemoglobin molecules called hemoglobin S which can distort red blood cells into a sickle cell shape or crescent shape. This makes it sticky and rigid and prone to getting trapped in small vessels, which blocks blood from reaching different parts of the body. This can cause pain and tissue damage.

Causes and Inheritance


SCD is caused by a point mutation in the β-globin chain of hemoglobin, causing glutamic acid to be replaced with the amino acid valine at the sixth position and forms hemoglobin S (HbS). The β-The types of sickle cell disease include the following:

  • Hemoglobin Sβ0 thalassemia
  • Hemoglobin Sβ+ thalassemia
  • Hemoglobin SC
  • Hemoglobin SD
  • Hemoglobin SE
  • Hemoglobin SS

Hemoglobin gene is found on the short arm of chromosome 11. Under low-oxygen conditions (being at high altitude, for example), the absence of a polar amino acid at position six of the β-globin chain promotes the non-covalent polymerisation (aggregation) of hemoglobin, which distorts red blood cells into a sickle shape and decreases their elasticity.

It is inherited in an autosomal recessive pattern, which means that both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition. In sickle cell anemia, a person who carries one copy of the mutated gene is said to be a carrier for the condition.

Types


The types of sickle cell disease include the following:

  • Hemoglobin Sβ0 thalassemia
  • Hemoglobin Sβ+ thalassemia
  • Hemoglobin SC
  • Hemoglobin SD
  • Hemoglobin SE
  • Hemoglobin SS

Image Source: National Institute of Health

Signs and Symptoms


Symptoms of sickle cell anemia usually show up at a young age. They may appear in babies as early as 4 months old, but generally occur around the 6-month mark.

  • Fussiness in babies
  • Fatigue and tiredness
  • Bedwetting from associated kidney problems
  • Jaundice - yellowing of the eyes and skin
  • Swelling and pain in hands and feet
  • Frequent infections
  • Frequent infections

Children are only at risk for sickle cell disease if both parents carry sickle cell trait. A blood test called a hemoglobin electrophoresis can also determine which type you might carry.

People from regions that have endemic malaria are more likely to be carriers. This includes people from:

  • Africa
  • India
  • Mediterranean
  • Saudi Arabia

Diagnosis


Prenatal testing looks for the sickle cell gene in the mother’s amniotic fluid.

In children and adults, one or more of the following procedures may also be used to diagnose sickle cell disease.

Detailed patient history

This condition often first appears as acute pain in the hands and feet. Patients may also have

  • severe pain in the bones
  • anemia
  • painful enlargement of the spleen
  • growth problems
  • respiratory infections
  • ulcers of the legs
  • heart problems

Your doctor may want to test you for sickle cell anemia if you have any of the symptoms mentioned above.

Blood tests

Several blood tests can be used to look for SCD:

  • Blood counts can reveal an abnormal Hb level in the range of 6 to 8 grams per
  • deciliter
  • Blood films may show RBCs that appear as irregularly contracted cells
  • Sickle solubility tests look for the presence of Hb S

Hb electrophoresis

Hb electrophoresis is always needed to confirm the diagnosis of sickle cell disease. It measures the different types of hemoglobin in the blood.

Treatment


A number of different treatments are available for SCD:

  • Rehydration with intravenous fluids helps red blood cells return to a normal state. The red blood cells are more likely to deform and assume the sickle shape if the individual is dehydrated
  • Treating underlying or associated infections is an important part of managing the crisis, as the stress of an infection can result in a sickle cell crisis. An infection may also result as a complication of a crisis
  • Blood transfusions improve transport of oxygen and nutrients as needed. Packed red cells are removed from donated blood and given to patients
  • Supplemental oxygen is given through a mask. It makes breathing easier and improves oxygen levels in the blood
  • Pain medication is used to relieve pain during a sickle crisis. You may need over-the-counter drugs or strong prescription pain medication like morphine
  • (Droxia, Hydrea) helps to increase production of fetal hemoglobin. It may reduce the number of blood transfusions
  • Immunizations can help prevent infections. Patients tend to have lower immunity

Bone marrow transplant has been used to treat sickle cell anemia. Children younger than 16 years of age who have severe complications and have a matching donor are the best candidates.

References