Definition and Overview
Sickle cell disease is a group of blood disorders wherein patients have abnormal haemoglobin, a vital component in red blood cells. Instead of the normal haemoglobin, patients with this condition have haemoglobin S, which has the characteristic sickle shape.
Sickle cell disease is most prominent in tropical areas, specifically in sub-Saharan Africa, where 75% of cases occur. Approximately 150,000 newborns in Nigeria alone are diagnosed with the condition every year. The condition is also common in the Middle East and India. Migration patterns from these regions into European countries have significantly increased the incidence of this condition in Europe. Meanwhile, in the United States, the condition occurs in about 1 out of every 5,000 people. Worldwide, all these account for approximately 300,000 children born with this condition every year. Sickle cell disease is responsible for more than 175,000 deaths each year. Approximately 50% of patients with this condition live past 50 years old.
Cause of Condition
Sickle cell disease is an inherited disorder, which means that the condition is passed on from parents to the child. The cause is a mutation in a specific gene, found on chromosome 11. This causes a defect in the production of beta globin component of haemoglobin. The inheritance pattern of the disease is autosomal recessive.
The mutation produces stiff red blood cells and increased blood viscosity. In patients with this condition, the elasticity of the red blood cells is decreased, preventing the cells from flexibly deforming and passing through small vessels. This results in episodes of occlusion in small blood vessels, leading to poor blood supply and decreased oxygen delivery to various organs, causing the symptoms of sickle cell crisis. Aside from this, sickle cell disease also results in the destruction of the red blood cells, also known as haemolysis. Although the body creates new blood cells to replace the destroyed ones, it is unable to catch up to the rate of blood cell destruction, resulting in anaemia.
Sickle cell disease is already present from the time a patient is born; however, the disease usually does not manifest until about five months of age. Screening is compulsory in the United States, and parents are informed even before the child develops any symptoms.
Early manifestations of the condition include swelling of the feet and hands associated with pain. Patients can also present with pallor, easy fatigue, and sluggishness, which can be attributed to anaemia. Some patients experience yellowing of the skin, a condition known as jaundice that is due to the destruction of large amounts of red blood cells. Chronic pain is also common, especially among adolescents and adults. The spleen is likewise typically affected; damage to this organ makes the patient prone to contracting infections. Patients can also present with leg ulcers, which may be recurrent or may not heal properly.
Some patients with sickle cell disease present with symptoms of the complications such as sudden, sharp pain. This is due to the blockage of blood flow in the blood vessels. Pain can be felt anywhere, but is common in the lower back and the lower and upper extremities. Necrosis of bones can also occur, and patients typically experience pain and difficulty in ambulating. This occlusive crisis may be triggered by several conditions, including illness, dehydration and stress.
Patients can also suffer a stroke, wherein blood flow to the brain becomes blocked. This can produce symptoms of weakness of one side of the body, slurring of speech, loss of balance or even subtle signs of cognitive dysfunction, to name a few. Anywhere from 10 to 20% of patients with sickle cell disease can suffer from a stroke by 45 years of age.
One of the most feared complications of the condition is acute chest syndrome wherein patients experience fever, chest pain, difficulty of breathing and low oxygen levels. Approximately one-fourth of all deaths due to sickle cell disease are caused by this complication.
Who to See and Types of Treatment Available
Sickle cell disease is best managed primarily by a haematologist, a doctor who is trained in the management of blood disorders. Early diagnosis is crucial to prevent the development of complications. Regular follow-up every 3-12 months is advised.
Blood testing is commonly performed to check for anaemia. Routine immunizations should also be given to prevent the development of infections. Aside from routine vaccines for children, patients with sickle cell disease should also receive regular influenza, pneumococcal and meningococcal vaccines.
Pain medications may be given to relieve pain while some complications may require hospitalization. Severe anaemia may require recurrent blood transfusions while stroke requires prompt management and close monitoring in a hospital setting. Patients who develop acute chest syndrome should also be brought to a hospital immediately so they can be given antibiotics and supportive therapy with oxygen right away.
Hydroxyurea is a drug that has been proven to be useful in the treatment of patients with sickle cell disease. Research has shown that it results in decreased occurrence of crises, the need for transfusions, pain episodes, and lower risk for the development of acute chest syndrome.
The only treatment that has been proven to be effective in sickle cell disease is bone marrow transplantation.
Saunthararajah Y, Vichinsky EP. Sickle cell disease: clinical features and management. In: Hoffman R, Benz EJ Jr, Silberstein LE, et al., eds. Hematology: Basic Principles and Practice. 6th ed. Philadelphia, Pa: Elsevier Saunders; 2012:chap 40.
Rees DC, Williams TN, Gladwin MT. Sickle-cell disease. Lancet. 2010;376(9757):2018-2031.