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Sickle-cell disease and other haemoglobin disorders

WHAT ARE HAEMOGLOBIN DISORDERS?

Haemoglobin disorders are inherited blood diseases that affect how oxygen is carried in the body. Haemoglobin disorders fall into two main categories: sickle-cell disease and thalassaemias.

  • Sickle-cell disease is characterized by a mutation in the shape of the red blood cell from a smooth, donut-shape to a crescent or half moon shape. The misshapen cells lack plasticity and can block small blood vessels, impairing blood flow. This condition leads to shortened red blood cell survival, and subsequent anaemia, often called sickle-cell anaemia. Poor blood oxygen levels and blood vessel blockages in people with sickle-cell disease can lead to chronic acute pain syndromes, severe bacterial infections, and necrosis (tissue death).
  • Thalassaemias are also inherited blood disorders. People with thalassemia are not able to make enough haemoglobin, which is found in red blood cells and carries oxygen to all parts of the body. When there is not enough haemoglobin in the red blood cells, oxygen cannot get to all parts of the body. Organs then become starved for oxygen and are unable to function properly. There are two major types of thalassaemia, alpha and beta, which are named for the two protein chains that make up normal hemoglobin. Alpha and beta thalassaemias have both mild and severe forms.

FACTS ABOUT HAEMOGLOBIN DISORDERS

  • It is estimated that each year over 300,000 babies with severe forms of these diseases are born worldwide; the majority in low and middle income countries.
  • Approximately 5% of the world’s population are carriers of a trait gene for sickle-cell disease or thalassaemia; The percentage of people who are carriers of the gene is as high as 25% in some regions.
  • These conditions are most prevalent in tropical regions; however population migration has spread these diseases to most countries.
  • Thalassaemias are the most common in Asia, the Mediterranean basin, and the Middle East.
  • Sickle-cell disease predominates in Africa.

WHAT CAUSES HAEMOGLOBIN DISORDERS?

Haemoglobin disorders are inherited from parents in much the same way as blood type, hair color and texture, eye colour and other physical traits.

Sickle-cell disease and thalaessemias can occur only when both parents have trait genes for the particular condition. A child who inherits two of the same trait genes - one from each parent - will be born with the disease. However this is not inevitable: a child of two carriers has only a 25% chance of receiving two trait genes and developing the disease, and a 50% chance of being a carrier. Most carriers lead completely normal, healthy lives.

HOW CAN HAEMOGLOBIN DISORDERS BE REDUCED?

Haemoglobin disorders can be effectively reduced through a strategic balance of disease management and prevention programmes.

Sickle-cell disease cannot be cured; however the condition can be managed by:

  • High fluid intake
  • Healthy diet
  • Folic acid supplementation
  • Pain medication
  • Antibiotics for infections

Thalassaemias require regular blood transfusions to maintain a healthy supply of haemoglobin and sustain life. As a result of multiple transfusions, organs become severely overloaded with iron and secondary treatment is needed to manage this condition. Thalassaemias can be cured by successful bone-marrow transplantation, however this procedure is expensive and not readily available in most settings.

The most cost-effective strategy for reducing the burden of haemoglobin disorders is to complement disease management with prevention programmes. Inexpensive and reliable blood tests can identify couples at risk for having affected children. This genetic screening is especially opportune before marriage or pregnancy, allowing couples to discuss the health of their family. Subsequent genetic counselling informs trait carriers of risks that may be passed along to their children and the treatment needed, if affected by a haemoglobin disorder. Prenatal screening of genetic diseases raises specific ethical, legal and social issues that require appropriate consideration.

WHO'S ACTIVITIES FOR PREVENTING AND CONTROLLING HAEMOGLOBIN DISORDERS

The governing bodies of the World Health Organization have adopted two resolutions on haemoglobin disorders. The resolution on Sickle-Cell Disease from the 59th World Health Assembly in May 2006 and the Resolution on Thalassaemia from the 118th meeting of the WHO Executive Board call upon affected countries and the secretariat of WHO to strengthen their response to these conditions.

Specifically, WHO will:

  • Increase awareness of the international community of the global burden of these disorders;
  • Promote equitable access to health services;
  • Provide technical support to countries for the prevention and management of these disorders; and
  • Promote and support research to improve quality of life for those affected.

WHO'S STRATEGY FOR PREVENTION AND CONTROL OF CHRONIC DISEASES

WHO’s work on haemoglobin disorders is integrated into the overall WHO chronic disease prevention and control framework of the Department of Chronic Disease and Health Promotion. The strategic objectives of the Department are to raise awareness about the global epidemic of chronic diseases; create healthy environments, especially for poor and disadvantaged populations; slow and reverse trends in common chronic disease risk factors such as unhealthy diet and physical inactivity; and prevent premature deaths and avoidable disability due to major chronic diseases.


Sources: US Department of Health; The World Health Organization


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