What is Sickle Cell Anaemia

Sickle cell anaemia is a structural abnormality of the haemoglobin chain in blood.

Statistics on Sickle Cell Anaemia

The main pathology of the sickle cell syndrome is an abnormality of the haemoglobin gene, the oxygen carrying protein of the bloodstream. The sickle cell form of this gene is most commonly carried by the African population, with approximately 8% of African Americans carrying the sicle cell disease gene. In other regions such as India and the Middle East, different abnormalities exist in the haemoglobin gene, causing a similar pattern of disease. The gene is relatively uncommon amongst caucasian populations.

Risk Factors for Sickle Cell Anaemia

Predisposing factors for the incidence of sickle cell syndromes include:

  • Family History – As this condition cannot be acquired, family history is the most important risk factor in the development of a sickle cell syndrome.
  • Race – The condition is more common in negro populations.
  • Local prevalence of malaria– As sickle cell disease protects against the development of malaria, the process of natural selection has increased the prevalence of sickle cell disease to 30% in some regions.

Progression of Sickle Cell Anaemia

Sickle cell syndromes are notable for the vast difference in severity between patients with different forms of the disease. The condition is universally inherited, yet its course may be mild and asymptomatic, or severe and disabling.

The main disease process occurring in sickle cell disease is the sudden destruction of red blood cells by “sickling.” The red blood cells of the patient with sickle cell anaemia are unstable, and take on a sickled non-functional form when the patient is subject to ceratin disease or physical stress.

Sickle cell anaemia varies from a mild symptomatic disorder to a severe haemolytic anaemia and recurrent severe painful crises. The variation in disease severity relates to the nature of the genetic mutation, which differs between each form of the disease.

The condition may present in childhood with anaemia and mild jaundice. The hand-and-foot syndrome due to infarcts of small bones is quite common in children and may result in digits of varying lengths.

In the older patient, blood vessel may be occluded owing to sickling of blood cells in the small vessels of any organ. Long-term problem associated with the disease include:

  • Susceptibility to infections, particularly to Streptococcus pneumoniae, which can cause a fatal meningitis or pneumonia. Bone infection can occur, often due to Salmonella;
  • Chronic leg ulcers due to poor blood flow to the limbs with sickle cell obstruction;
  • Gallstones– pigment stones from persistent red blood cell destruction;
  • Degeneration of bone, particularly of the hips;
  • Blindness due to retinal attachment and/or retinal disease; and
  • Chronic renal disease.

How is Sickle Cell Anaemia Diagnosed?

As the main pathology of this condition occurs in the blood, numerous blood tests are required to obtain an accurate diagnosis of this disease. Reduced numbers of normal red blood cells, and the presence of abnormal shaped cells allows the diagnosis to be made. If the initial blood tests cannot identify the problem, the blood is treated with an agent to bring out sickling in blood affected by sickle cell disease. A definitive diagnosis required a process called haemoglobin electrophoresis, which enables the condition to be diagnosed and typed.

Prognosis of Sickle Cell Anaemia

Some patients die in the first few years of life from either infection or episodes of sequestration. However, there is marked individual variation in the severity of the disease and some patients have a relatively normal life-span with few complications.

How is Sickle Cell Anaemia Treated?

The steady state anaemia does not require any treatment. Precipitating factors should be avoided or treated quickly. These include infection, dehydration, hypothermia, acidosis and hypoxia.

There are also a number of complications of this condition that require management should they arise. These include painful episodes, swollen painful joints, neurological problems, and problems relating to blood vessel blockage by sickling cells which may affect the kidneys, intestines, spleen and liver. Gallbladder problems are also more common in sickle cell disease which should be managed as usual.

Acute attacks require supportive therapy with intraqvenous fluids, oxygen, antibiotics and adequate analgesia. Antibiotics may be given to prevent infection. Folic acid is given to pregnant women and those with severe haemolysis to reduce the risk of pregnancy complications.

The acute sickle chest syndrome is the most serious consequence of sickle cell disease. Management is with pain relief, inspired oxygen, antibiotics and exchange transfusion, occasionally ventilation may be necessary.

Regular transfusions are given only if there is severe anaemia or if patients are having frequent painful crises. Before elective operations and during pregnancy, transfusions may be used to reduce the risk of adverse events suring surgery. Exchange transfusions may be necessary in patients with severe or recurrent crises, or before emergency services. Transfusion and removal of the spleen may be life-saving for young children with the accumulation of sickle cells within the spleen.

Sickle Cell Anaemia References

  1. Braunwald, Fauci, Kasper, Hauser, Longo, Jameson. Harrison’s Principles of Internal Medicine. 15th Edition. McGraw-Hill. 2001
  2. Cotran, Kumar, Collins 6th edition. Robbins Pathologic Basis of Disease. WB Saunders Company. 1999.
  3. Kumar P, Clark M. CLINICAL MEDICINE. WB Saunders 2002 Pg 545-549.
  4. Longmore M, Wilkinson I, Torok E. OXFORD HANDBOOK OF CLINICAL MEDICINE. Oxford University Press. 2001

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