Sickle cell anaemia

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Overview

Sickle cell is a disease that is inherited and may occur as a trait (you carry one mutated gene from one of your parents) or as the disease (you carry two mutated genes, one from each of your parents). The trait usually causes little or no problem but can continue to be passed on to your children. The disease may cause significant health problems, called 'crises', throughout life.

A crisis is a painful condition brought on by lack of oxygen in the red blood cells, causing them to change shape. They become hypoxic, and shaped like a sickle, thus the name of the disease. Infection, dehydration, or change in altitude are among the events that can cause a crisis.

Haemoglobin in the red blood cells carries oxygen to all parts of the body. In sickle cell anaemia, haemoglobin becomes insoluble, and the red blood cells can become rigid, pointy and sticky. They can then clog blood vessels, causing pain and damage. A low red blood cell count also may occur due to the destruction of these cells (haemolytic anaemia). Body organs most likely to be severely affected include the spleen, kidneys and bone marrow. The eyes and top of the femur (thigh bone) are also at risk because there are few arteries in these areas.

The sickle cell abnormality is found predominantly in people of African ancestry but may also be found in those who can trace their roots to the Mediterranean area, South and Central America, the Middle East, India and the Caribbean.

A screen for this condition may include several tests: a haemoglobin electrophoresis to identify the specific types of haemoglobin present, measurement of haemoglobin A2 and F (adult and fetal), a full blood count (FBC) to detect anaemia, and a reticulocyte count.

Complications of sickle cell disease may include pain, stroke, increased risk of infection, prolonged painful erection of the penis (priapism), acute chest syndrome, acute splenic sequestration and leg ulcers. Signs of sickle cell crisis include fever, mild jaundice (yellowing of the skin and whites of the eyes), chest pain and shortness of breath. For a more complete list of both complications and signs of crisis, visit the Royal Children’s Hospital, Melbourne: Clinical Practice Guidelines.

There are three types of sickle cell crisis: aplastic, haemolytic, and painful.

  • Aplastic – This type is due to infections, particularly parvoviruses, and results in a decrease in production of red blood cells. It may be self-limiting in 5-10 days.
  • Haemolytic – This anaemia is more severe, resulting in a sudden increase in the destruction of red blood cells. The bone marrow cannot produce cells fast enough to compensate for the loss, resulting in a critical decrease in haemoglobin and haematocrit. Transfusions are frequently needed to replace the red blood cells. In children, repeated crises could cause an enlarged spleen, which increases the risk of it rupturing.
  • Painful – This type is associated with severe pain due to the rigid sickle cells blocking the blood vessels, causing damage to cells and organs. It usually lasts 4-6 days, but may persist for weeks.

Newborns with sickle cell disease are often placed on penicillin to prevent pneumonia and other infections. Adults may be treated with hydroxyurea, which has been found to reduce the number of crises and lessen the severity of those that do occur. Intravenous fluids and oxygen are given in crises. Severe crises may also be treated with blood transfusion or exchange transfusion to raise the red blood cell count and reduce the number of sickle cells.

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