Sickle cell anaemia is a lifelong inherited blood disorder that changes the shape of red blood cells, turning them from flexible round discs into rigid crescent-shaped cells that struggle to move through blood vessels. This condition affects how oxygen travels through the body and can cause severe pain, frequent infections, and damage to vital organs. While there is currently no universal cure, advances in medical care mean many people living with sickle cell anaemia can now manage their symptoms effectively and lead meaningful lives well into their 50s and beyond.

How Common Is Sickle Cell Anaemia Around the World?

Sickle cell anaemia affects approximately 70,000 to 100,000 people in the United States alone, making it the most common inherited blood disorder in the country. The condition does not affect all populations equally. It is particularly prevalent among people of African descent, with around 1 in 365 Black Americans born with the disease and about 1 in 12 carrying the gene that can cause it.^[1][4]

The disease also commonly affects people with Hispanic backgrounds, particularly those from Central and South America. Additionally, individuals with ancestry from the Middle East, Mediterranean regions, southern Europe, and parts of Asia, including India, face higher risks. This geographical pattern is connected to historical patterns of malaria, as carrying one copy of the sickle cell gene actually provides some protection against that mosquito-borne disease.^[3][6]

All newborns in the United States are now routinely screened for sickle cell disease as part of standard newborn screening programs, which test babies shortly after birth for various serious conditions. This early detection allows healthcare providers to start preventive treatments immediately, which has dramatically improved outcomes for affected children. In many countries, screening is also offered to pregnant women to assess whether their future child might be at risk.^[5]

What Causes Sickle Cell Anaemia?

Sickle cell anaemia is caused by changes, known as genetic mutations, in a specific gene called the HBB gene. This gene contains the instructions for making a protein called beta-globin, which is an essential part of hemoglobin—the protein inside red blood cells that carries oxygen from the lungs to all parts of the body. When the HBB gene is mutated, it produces an abnormal form of hemoglobin known as hemoglobin S (HbS).^[2][4]

This abnormal hemoglobin causes red blood cells to become stiff and take on a distinctive crescent or “sickle” shape, especially when they release their oxygen. Normal red blood cells are soft, round, and flexible, which allows them to squeeze through even the tiniest blood vessels. Sickled cells, however, are rigid and sticky. They get stuck in small blood vessels, blocking blood flow and preventing oxygen from reaching tissues and organs. This blockage is what causes the pain and complications associated with the disease.^[1][7]

Sickle cell anaemia is inherited, meaning it is passed down from parents to their children through genes. A child develops sickle cell anaemia only if they inherit one sickle cell gene from each biological parent—a total of two copies. If both parents have either sickle cell disease themselves or carry the sickle cell gene (known as having sickle cell trait), there is a 1 in 4 chance with each pregnancy that their child will be born with the disease. The child’s parents may not have the disease themselves but may simply be carriers of one changed gene.^[3][5]

People who inherit only one sickle cell gene and one normal gene have sickle cell trait. They typically do not experience symptoms of the disease and live normal lives. However, they can pass the gene to their children, which is why genetic counseling is recommended for couples considering having children when one or both partners carry the trait.^[6]

Who Is at Higher Risk?

The primary risk factor for sickle cell anaemia is family history and ethnic background. Because the condition is genetic, anyone whose biological parents both carry at least one copy of the sickle cell gene is at risk. The disease is most common in people of African or Caribbean descent, but also affects those with family roots in Central and South America, the Middle East, India, and Mediterranean countries such as Greece, Turkey, and Italy.^[6][7]

Unlike many other diseases, sickle cell anaemia is not influenced by lifestyle choices such as diet, exercise, or environmental exposures. It is present from birth because it results from genetic changes inherited from both parents. However, once someone has the disease, certain situations and behaviors can increase the risk of triggering painful complications, known as pain crises or sickle cell crises. These triggers include dehydration, extreme temperatures (either hot or cold), high altitudes where oxygen levels are lower, strenuous physical activity, stress, infections, and smoking or alcohol consumption.^[14][17]

Because the condition affects the immune system, particularly the spleen, people with sickle cell anaemia are more vulnerable to infections. Young children are especially at risk, which is why preventive measures like vaccinations and daily antibiotics are critical.^[4]

Common Symptoms and How They Affect Daily Life

Symptoms of sickle cell anaemia usually begin to appear when a baby is around 5 to 6 months old, although the condition is present from birth. The symptoms vary widely from person to person, and they can change over time as the body produces more sickled cells. Some people experience mild symptoms and lead relatively normal lives, while others face severe complications requiring frequent medical attention.^[1][4]

One of the earliest and most noticeable symptoms is anaemia, a condition where the body does not have enough healthy red blood cells to carry sufficient oxygen. Sickled cells break apart and die much faster than normal red blood cells—typically within 10 to 20 days instead of the usual 120 days. This leads to a constant shortage of red blood cells, causing extreme tiredness, weakness, and paleness. In babies, this may show up as unusual fussiness or irritability.^[1][5]

Another common symptom in infants is painful swelling of the hands and feet, often one of the first signs that a baby has sickle cell anaemia. This happens when sickled cells block blood vessels in these areas, preventing blood from flowing properly. The swelling can be very painful for the baby.^[4]

Many people with sickle cell anaemia also develop yellowish discoloration of the skin and the whites of the eyes, known as jaundice. This happens because the liver has to process a buildup of a substance called bilirubin, which is released when red blood cells break down rapidly.^[4]

Frequent infections are another hallmark of the disease. Sickle cell anaemia damages the spleen, an organ that plays a key role in fighting infections. As a result, the immune system becomes weakened, making people more susceptible to serious bacterial infections, particularly in childhood. Thanks to widespread use of preventive antibiotics and vaccinations, the risk of severe infections has been greatly reduced, but vigilance remains essential.^[4][14]

Perhaps the most challenging symptom for many people is severe pain, which occurs during what are called pain crises or vaso-occlusive crises. These episodes happen when sickled cells get stuck in blood vessels and block the flow of blood to tissues. The lack of oxygen reaching the tissues causes sudden, intense pain that can last for hours or even days. The pain can occur anywhere in the body but is most common in the arms, legs, chest, back, and joints. Some people experience only a few pain crises a year, while others may have a dozen or more, significantly impacting their quality of life.^[1][2]

Over time, repeated blockages of blood flow can lead to serious complications including strokes, lung problems such as acute chest syndrome, vision loss, kidney disease, and damage to other organs. Delayed growth and puberty are also common in children with the disease.^[2][4]

How to Reduce Your Risk and Prevent Complications

Since sickle cell anaemia is an inherited genetic condition, there is no way to prevent being born with it. However, there are important steps people can take to reduce the risk of serious complications and manage the disease more effectively. Prevention in this context means both avoiding triggers that can cause pain crises and taking proactive measures to protect overall health.^[16]

One of the most important preventive measures is staying well-hydrated. Drinking plenty of water—at least 8 to 10 glasses a day—helps keep blood flowing smoothly and reduces the risk of sickled cells clumping together. Dehydration is a common trigger for pain crises, so people with sickle cell anaemia should make a conscious effort to drink fluids regularly, especially during hot weather or physical activity.^[14][21]

Avoiding extreme temperatures is also crucial. Both very hot and very cold conditions can trigger pain episodes. People should dress appropriately for the weather, avoid sudden temperature changes (such as jumping into a cold pool), and be cautious in environments where temperature control is difficult.^[17]

Preventing infections is another cornerstone of managing sickle cell anaemia. This starts with vaccinations. People with sickle cell disease should receive all routine childhood vaccines, as well as annual flu shots and vaccines for pneumonia and meningitis. Daily antibiotics, usually penicillin, are often prescribed for young children starting in infancy and continuing until at least age 5 to protect against life-threatening bacterial infections. Some adults may also need to continue taking antibiotics if they have had serious infections or if their spleen has been removed.^[10][14]

Good hygiene practices, such as frequent handwashing and safe food preparation, also help reduce infection risk. People with sickle cell disease should seek medical attention promptly at the first sign of infection, such as fever, because even common illnesses can quickly become dangerous.^[14][21]

Regular medical checkups are essential for monitoring the disease and catching complications early. Babies and young children should see their doctor every few months, while older children and adults should have checkups at least once a year. Special tests, such as transcranial Doppler ultrasound, can help identify children at high risk for stroke, allowing doctors to take preventive action, such as regular blood transfusions.^[9][14]

Starting at age 10, people with sickle cell disease should have yearly eye exams to check for damage to the retina, which can lead to vision loss if left untreated.^[14]

Lifestyle choices also matter. While regular physical activity is important for maintaining overall health, it should be moderate and not overly strenuous. People should avoid activities that cause severe shortness of breath or exhaustion. Rest is just as important as activity. Avoiding smoking and excessive alcohol consumption is critical, as both can trigger complications like acute chest syndrome and dehydration.^[17][24]

Stress management techniques, such as breathing exercises, meditation, or other relaxation methods, can also help reduce the risk of pain crises, as stress is a known trigger.^[17]

What Happens Inside the Body

Understanding what goes wrong inside the body in sickle cell anaemia helps explain why the disease causes such varied and serious problems. The process starts at the molecular level, with the production of abnormal hemoglobin. Hemoglobin is the protein inside red blood cells that binds to oxygen in the lungs and carries it throughout the body. In sickle cell anaemia, the mutation in the HBB gene leads to the production of hemoglobin S instead of normal hemoglobin A.^[2][7]

When hemoglobin S releases its oxygen to body tissues, it behaves differently than normal hemoglobin. The molecules of hemoglobin S stick together and form long, rigid chains inside the red blood cell. These chains distort the cell’s shape, transforming it from a smooth, flexible disc into a stiff, crescent or sickle shape. Sickled cells are fragile and break apart easily, leading to their premature death—this is why people with sickle cell anaemia are constantly anaemic.^[1][2]

The rigid, sickle-shaped cells also have trouble moving through small blood vessels. Normal red blood cells are soft and can bend and squeeze through narrow capillaries, but sickled cells are inflexible and sticky. They tend to clump together and get stuck, blocking the flow of blood. This blockage prevents oxygen from reaching tissues and organs downstream, causing tissue damage and triggering pain. When this happens repeatedly over time, it can lead to permanent organ damage.^[1][4]

The spleen is one of the organs most affected by sickle cell disease. The spleen filters the blood and helps fight infections, but repeated blockages by sickled cells cause damage that impairs its function. In many children with sickle cell anaemia, the spleen becomes so damaged that it stops working properly, a condition known as functional asplenia. This is why people with the disease are so vulnerable to infections.^[4]

The kidneys are also frequently affected. The low-oxygen environment inside the kidney, combined with repeated vaso-occlusive episodes, can damage the delicate filtering structures. Over time, this can lead to chronic kidney disease. Similarly, blockages in blood vessels supplying the brain can cause strokes, which are a leading cause of disability and death in people with sickle cell disease, particularly in children.^[2]

The lungs are vulnerable to a serious complication called acute chest syndrome, which occurs when sickled cells block blood vessels in the lungs. This can cause chest pain, fever, difficulty breathing, and dangerously low oxygen levels. It is one of the most common reasons people with sickle cell anaemia are hospitalized.^[1]

Over a lifetime, the cumulative effects of repeated blockages, chronic anaemia, and ongoing inflammation can affect nearly every organ system, including the heart, liver, eyes, and bones. This explains why comprehensive, lifelong medical care is so essential for people living with sickle cell anaemia.^[2]