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Written By: Editorial Team | Updated : August 6, 2019 9:27 PM IST
A shortage of healthy red blood cells can slow growth in infants and children and delay puberty in teenagers. © Shutterstock
Your blood is the fuel that runs your whole body. Any problem with it can affect total health. There are many blood disorders that can have a debilitating affect on the body. While anaemia is a common condition, bleeding disorders like haemophilia, blood clots and blood cancers like leukaemia, lymphoma and myeloma are also prevalent. Other than these, there are some inherited conditions like sickle cell disease and beta-thalassemia.
For the first time now, researchers from Fred Hutchinson Cancer Research Center have successfully edited the genetic makeup of a specialised subset of adult blood stem cells that are the source of all cells in the blood and immune system. They used CRISPR-Cas9 to edit long-lived blood stem cells to reverse the clinical symptoms observed with several blood disorders, including sickle cell disease and beta-thalassemia.
According to them, efficient modification of targeted stem cells could reduce the costs of gene-editing treatments for blood disorders and other diseases while decreasing the risks of unwanted effects that can occur with a less discriminating approach. This can help millions of people with blood diseases. This study was published inScience Translational Medicine. This is good news indeed for people with sickle cell disease.
This is a common hereditary blood disorder in which, the otherwise, round, red blood cells look like sickles. In a healthy person, haemoglobin is disc shaped, smooth and flexible. This allows the red blood cells to flow easily through the blood stream.
But in people with sickle cell disease, the haemoglobin proteins clump together and look like rods. This causes the red blood cells to become rigid and curved. These cells block the flow of blood, causing problems like unexplained and sudden pain, swollen limbs and poor vision among others. It includes disorders like sickle anaemia and thalassaemia.
Since the disorder is hereditary, it is present at birth, but most children show the signs and symptoms only after the age of 4-5 months. When the babies with SCD are 4-5 months old, foetal haemoglobin is replaced by sickle cell haemoglobin (HbS).
Symptoms of sickle cell disease may vary from person to person and also change over time. Let us take a look at some of the symptoms.
Red blood cells usually live for about four months and then they are replaced by new red blood cells. But sickle cells die in 10 to 20 days, much before new cells can be formed, leaving a shortage of red blood cells. And without enough red blood cells, your body can't get the oxygen, causing fatigue. You might also have shortness of breath, dizziness, and headaches.
Episodes of pain, called pain crises, occur suddenly, out of nowhere, and are sharp, stabbing, and intense. Pain can occur wherever the sickle-shaped red blood cells block blood flow in the bloodstream. It can last for a few hours to a few weeks. The frequency varies from a few pain episodes in some people to a dozen or more crises a year in others. At times, it may require hospitalisation.
Also called dactylitis, the swelling is caused by sickle-shaped red blood cells blocking blood flow to the hands and feet. Along with the pain, there may be coldness of hands and feet. This is usually one of the early signs of the disorder occurring in young children.
Sickle cells can damage the spleen that fights infection, leaving you more vulnerable to infections.
Since a large number of red blood cells break down and cause low levels of circulating red blood cells, the skin becomes yellow in colour. Sometimes, the whites of the eyes also become yellowish. This is termed icterus.
Red blood cells provide the body with the oxygen and nutrients needed for growth. A shortage of healthy red blood cells can slow growth in infants and children and delay puberty in teenagers.
Tiny blood vessels that supply blood to your eyes may become plugged with sickle cells. This can damage the retina the portion of the eye that processes visual images. This can cause vision problems.
Sickle cell anemia can lead to a host of complications. According to the Centers for Disease Control and Prevention, some of the complications are as follows.
This is a life-threatening complication that causes chest pain, difficulty breathing, coughing, and fever.
Here, the sickle cells get trapped in the spleen and cause it to enlarge. Seek help if you suddenly feel weak, your heart beats faster, you have intense belly pain on the left side, and you feel extremely thirsty.
You may experience vision loss, including blindness. This is because the sickle cells block the blood vessels in the eye and damage the retina.
Ulcers usually on the lower part of the leg are a common complication of this condition. It is usually seen in boys and men aged 10 years to the 50s.
This is another serious complication. It happens because the sickle cells cause blood clots in the vein and lungs, respectively.
This happened due to chronic deprivation of oxygen-rich blood to the kidneys. Renal involvement is usually more severe in sickle cell anaemia than in compound heterozygous types of SCD such as beta-thalassaemia and is typically mild sickle cell trait. Kidney damage leads to lower life expectancy of patients with this condition.
Normally, the haemoglobin molecule picks up oxygen in the lungs and releases it when the red cells in the bloodstream reach the tissues such as muscles. However, it is different in case of sickle haemoglobin. After picking up the oxygen, sickle haemoglobin releases it in the tissues. But the molecules tend to stick together and form long chains or polymers. This is called polymerisation. These rigid polymers distort the cell and cause it to bend out of shape.
When the red cells return to the lungs and pick up oxygen again, the haemoglobin molecules become 'normal' again. Red cells circulate in the bloodstream four times in one minute. Sickle haemoglobin undergoes repeated episodes of polymerisation and depolymerisation. This ultimately damages the haemoglobin and the red cell itself. This is called haemolysis.
Polymerisation causes the iron-rich haeme component of haemoglobin to be released from the protein into the red cell membrane, causing the membrane to stiffen. The iron promotes the formation of very dangerous compounds, called reactive oxygen species or ROS, which again damage the red cells.
The bone marrow, where these red cells are produced, increase production dramatically but is unable to keep pace with the destruction. The result is anaemia.
