What is Sickle Cell Disease
(Published in the newspaper Amigoe on the 11th of February 2026)
Sickle cell disease is an inherited blood disorder that affects millions of people worldwide and has its origins in a fascinating interplay between genetics, evolution and infectious diseases. The condition occurs when the red blood cells do not take on the normal round and flexible shape, but change into a stiff, crescent-shaped structure, that resembles a sickle. These sickle-shaped cells easily block small blood vessels and are also broken down much faster than healthy red blood cells. This combination of blockage and breakdown causes the body to receive too little oxygen and chronic anemia develops, alternating with periods of severe pain, so-called sickle cell pain crises.
Red blood cells from a healthy person and someone suffering from sickle cell disease
Cause
The root cause of the disease lies in the gene, which contains the blueprint for the β chain of hemoglobin, the protein responsible for binding and transporting oxygen. The sickle cell mutation changes a single amino acid in this β chain. That seems like a small change, but it has major consequences. The aberrant hemoglobin clumps together when it contains little oxygen, causing the red blood cell to deform into a sickle.
Interestingly, newborn babies with sickle cell disease have few symptoms in the first weeks to months of life, as they have mostly fetal hemoglobin. This type of hemoglobin does not contain β chains and therefore cannot sickle. Only when the body switches to adult hemoglobin over time, which does contain the β chain, do the abnormalities become visible.
Origin
The origin of the sickle cell gene lies in areas where malaria was common in the past, such as Sub-Saharan Africa, parts of the Middle East, India and Mediterranean regions. The spread of the mutation is a classic example of evolution by natural selection. People who carry only one copy of the abnormal gene, so-called carriers, produce both normal hemoglobin and part of the abnormal hemoglobin.
As a result, their red blood cells have subtle changes that make it harder for the malaria parasite to develop. This means that carriers are more resistant to severe malaria and therefore had a greater chance of surviving and reproducing. In this way, the gene persisted for generations and even increased in frequency. This evolutionary mechanism is known as balancing selection. A harmful hereditary trait remains present because in certain circumstances it gives a survival advantage.
Spread around the world
Historical migration, including the transatlantic slave trade but also modern migration flows, eventually spread the sickle cell gene all over the world. Today, sickle cell disease occurs in North and South America, Europe, the Caribbean and the Middle East. Worldwide, an estimated 20 to 25 million people suffer from the disease, while hundreds of millions are carriers of the gene.
Inheritance
Genetically, the disease is inherited autosomal recessively. That means that a person will only develop sickle cell disease if he or she inherits two copies of the mutant gene, one from each parent. Someone with only one abnormal copy is a carrier, but usually healthy. If both parents are carriers, each pregnancy has a 25% chance of having a child with sickle cell disease, 50% of a carrier and 25% of a healthy child. Thanks to modern genetic techniques, carrier status is fairly easy to determine, allowing parents to make more informed choices today.
Symptoms
The symptoms of sickle cell disease vary greatly between patients, but a few signs are common. The most notorious are the pain crises, which can occur when sickle cells block small blood vessels, often in the bones, chest, or abdomen. These crises can last for hours to days and sometimes require hospitalization. The continuous breakdown of red blood cells leads to chronic anemia, with complaints such as fatigue, dizziness and shortness of breath. Because the spleen, an important organ in the immune system, is damaged in many patients due to repeated blockages, infections are a major risk, especially at a young age. Other possible complications include strokes, lung problems, kidney damage, and growth retardation.
Blood vessels blocked by sickle-shaped red blood cells
Treatment
The treatment of sickle cell disease has come a long way in recent decades. An important pillar of care is the prevention of infections. Young children are often given antibiotics and special vaccinations for a long time, because infections can trigger a sickle cell crisis or be life-threatening.
In addition, hydration plays an important role. Drinking enough helps keep the blood thinner, making cells less likely to get stuck. Also, folic acid is given to patients with sickle cell disease to support the bone marrow in making extra red blood cells, because the need for extra red blood cells is much greater than normal due to the increased breakdown.
One of the most effective medications is hydroxycarbamide (hydroxyurea). This drug stimulates the production of fetal hemoglobin. Fetal hemoglobin does not sickle. However, after birth, the gene to produce fetal hemoglobin is suppressed and the production of adult hemoglobin is switched on. Adult hemoglobien can sickle in patients with sickle cell disease. However, hydroxyurea reduces the suppression of fetal hemoglobin production. As a result, an adult can produce more fetal hemoglobinagain and pain crises decrease and the red blood cells function better. For many patients, this means a significant improvement in their quality of life.
Blood transfusions are also widely used, especially to treat severe anemia and to prevent complications such as strokes. Regular transfusions can reduce the percentage of abnormal hemoglobin in the blood and thus reduce the risk of problems. However, they can lead to iron overload in the long term, requiring additional medication to remove excess iron from the body.
Sickle cell disease is therefore more than a medical condition. It is an example of evolution in action, a reminder of the global impact of malaria, and a disease that poses major challenges and important innovations for modern medicine. Sickle cell disease was for centuries a result of a genetic adaptation to a deadly infectious disease. However humanity now seems to be on the verge of definitively turning the tide with the help of advanced biotechnology and bringing the disease closer to a complete cure. Curing sickle cell disease is the subject of the following article.
Start writing here...