Sickle cell anemia is a genetic disease affecting the red blood cells causing abnormal versions of hemoglobin referred to as hemoglobin S, or sickle hemoglobin. It results in an anomaly in the oxygen-carrying protein known as hemoglobin present in red blood cells. The disease gets its name due to a sickle shape, which is a C-shaped farm tool, of the red blood cells.
Distinctive features of sickle cell anemia include a low number of red blood cells causing anemia, repeated infections, and periodic episodes of pain (bout). Sickle cell anemia causes significant morbidity and mortality.
CAUSES OF SICKLE CELL ANEMIA
Sickle cell anemia is a genetic disease. The disease is inherited from one or both parents contains two sickle cell genes or sickle cell trait (one sickle cell gene). Child born with one defective gene is the carrier of the disease. The disease is expressed in children if the gene is passed by both parents.
Sickle cell anemia is a result of mutation in the gene (known as HBB gene) that helps in production of iron-rich compounds that makes blood red as well as enables these red blood cells to carry oxygen from the lungs to other organs of the body. This compound is known as hemoglobin.
Hemoglobin consists of four protein subunits out of which two subunits are called alpha-globin and other two subunits are called beta-globin. The HBB gene is responsible for making beta-globin found on chromosome 11. One specific type of HBB gene mutation results in an abnormal version of beta-globin referred to as hemoglobin S (HbS).
Particularly in people with sickle cell anemia, minimum one of the beta-globin subunits present in hemoglobin is substituted with hemoglobin S. This substitution results in abnormal versions of beta-globin that distort the red blood cells into a sickle like shape that die prematurely leading to anemia. These inflexible, sickle-shaped red blood cells can get stuck in small blood vessels and cause serious medical complications that could be fatal.
Normal red blood cells are a biconcave disc shape with elasticity, which allows the cells to collapse to pass through thin capillaries. But due to sickle cell disease, low oxygen tension promotes red blood cells to sickle.
These repeated episodes of collapsing damage the cell membrane by decreasing the cell’s elasticity. Thus the cells fail to return to normal shape when oxygen tension is reinstated. As corollary, these rigid red blood cells are not capable of deforming as they pass through thin capillaries causing vessel occlusion and ischaemia.
The destruction of these red blood cells, because of their shape, causes anemia. The bone marrow tries to compensate for the damaged red blood cells but is unable to match the rate of destruction. The damaged red blood cell lasts about 10-20 days in comparison to 90-120 days of a normal blood cell.
SYMPTOMS OF SICKLE CELL ANEMIA
The symptoms vary from individual to individual and change over a period of time. Children born with sickle cell anemia tend to show the first symptom around 5 months of age. The symptoms include:
- Anemia – The shortage of red blood cells due to short life span (approximately 10-20 days) of the damaged cells leads to anemia. Due to anemia the body would look pale.
- Fatigue – Due to loss of a high number of red blood cells, enough oxygen is not supplied throughout the body leading to fatigue.
- Pain crises – These periodic bouts or episodes of pain are the main symptom of sickle cell anemia. Sickle-shaped red blood cells tend to block the blood flow through the tiny blood vessels or capillaries, causing pain in the chest, abdomen, joints, and bones. The intensity and frequency of pain can vary, and sometimes hospitalization might be required. Adolescents or adults can have chronic pain that can be caused from bone and joint damage, ulcers, and other causes.
- Hand and feel swelling –The blockage of the capillaries or blood vessels by the sickle-shaped red blood cells causes swelling in hand and feet.
- Infections – The sickle-shaped red blood cells can cause damage to tissues causing ulcers. If the spleen is damaged it can lead to frequent infections.
- Impaired Vision – The sickle cells can cause damage to blood vessels supplying oxygen to the retina as well as damage the retina leading to vision problems like impaired vision.
- Slow development – Red blood cells provide oxygen and nutrients needed for growth to the body. A shortage of the healthy red blood cells results in slow growth in infants and children as well as delays puberty in teenagers.
DIAGNOSIS OF SICKLE CELL ANEMIA
Blood test that checks for hemoglobin S protein to detect sickle cell anemia. The test would first check for the sickle hemoglobin and a second blood test confirms the hemoglobin S diagnosis. It can be detected in unborn babies by collecting samples of amniotic fluid from a mother’s womb or from the placenta. The test would detect the mutated HBB gene.
TREATMENT OF SICKLE CELL ANEMIA
Currently blood and bone marrow transplant are the only cure for sickle cell anemia. All other treatment regimes focus on managing the pain, other symptoms and complications due to sickle-shaped blood cells. A hematologist would recommend medicines and other therapies for underlying conditions.
Medicines – The pain episodes are severe, thus hydroxyurea (Droxia, Hydrea, Siklos) helps in lowering the intensity and frequency of pain crises and curb other complications such as infections and anemia. Hydroxyurea is helpful in reducing frequent painful episodes, recurrent chest crises, or severe anemia. Other painkillers like crizanlizumab (Adakveo) and L-glutamine oral powder (Endari) given as an injection, are also prescribed to ease pain. Medications like Voxelotor (Oxbryta) help fight with anemia. In children, penicillin has shown reduced chance of contracting a severe infection caused by the pneumococcus bacteria.
Transfusion – It is recommended to treat and prevent complications caused by sickle cell anemia. It is categorized as:
- Acute transfusions to treat complications like acute stroke, acute chest crisis, and multi-organ failure caused by sickle-shaped red blood cells.
- Red blood cell transfusions increase the quantity of red blood cells in addition to providing normal red blood cells with more flexibility unlike red blood cells with sickle hemoglobin.
- Regular or ongoing blood transfusions for people suffering from an acute stroke that reduce the chances of having another stroke. This approach is also used to treat complications that do not get better with hydroxyurea or complications like alloimmunization that makes it difficult to find a matching unit of blood for a future transfusion, infection, and iron overload.
Blood and Bone Marrow Transplant – This is the only cure currently for sickle cell anemia with about 85% of success rate especially in children (when donor is Human leukocyte antigen matched). The transplant is difficult as either the patient is old for a transplant or does not contain a compatible genetic match to be a donor. A well-matched donor is required for a patient to have the greater chance of successful transplant.
OUTLOOK
Sickle cell anemia is an inherited disease causing frequent and painful sickle cell crises to some patients while others might rarely have attacks. This is a lifelong illness and with effective treatments the symptoms can be reduced and life can be prolonged
If you or anyone you know is suffering from sickle cell anemia, our expert providers at Specialty Care Clinics will take care of your health and help you recover.
Call us on (469) 545-9983 to book an appointment with Dr. Ahsan Ali.