Sickle-cell disease is characterized by a modification in the shape of the red blood cell from a smooth, donut-shape into 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).

Approximately 5% of the world’s population are healthy carriers of a 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

Thalassaemias are also inherited blood disorders.

• People with thalassaemia are not able to make enough haemoglobin, which is found in red blood cells.
• 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 haemoglobin. Alpha and beta thalassaemia have both mild and severe forms.

What causes Sickle cell disease?

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

Sickle-cell disease and severe forms of thalassaemia (thalassaemia major) can occur only when both parents are carriers of 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, 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.

https://www.afro.who.int/health-topics/sickle-cell-disease