Sickle cell anemia affects nearly every major body system. Because the disease changes the shape and lifespan of red blood cells, and because those cells travel everywhere blood flows, the damage extends far beyond the bloodstream itself. The organs most commonly affected include the brain, lungs, kidneys, spleen, liver, bones, eyes, and reproductive organs.
Blood and Immune System
The most fundamental damage happens to red blood cells themselves. When oxygen levels inside a red blood cell drop, the defective hemoglobin forms long rods that stretch the cell into a rigid, crescent shape. A normal red blood cell lives about 120 days. A sickled cell lasts only 10 to 20 days. The body can’t replace them fast enough, which leads to chronic anemia, leaving you fatigued and short of breath even during routine activities.
The spleen, which filters blood and fights certain infections, takes heavy damage early in life. Sickled cells clog the spleen’s tiny blood vessels, gradually destroying the organ’s function. By age 5, 94% of children with sickle cell anemia have what’s called functional asplenia: the spleen is still physically present but no longer works. Without a functioning spleen, the body becomes dangerously vulnerable to infections from encapsulated bacteria, particularly the type that causes pneumococcal disease. This is why children with sickle cell anemia start preventive antibiotics in infancy.
Brain and Nervous System
Sickle cells can block blood flow to the brain, causing strokes. Before modern prevention practices, children with sickle cell anemia had roughly an 11% chance of having a stroke before age 20. That risk is now managed through annual ultrasound screening of the blood vessels in the brain, recommended for children ages 2 through 16. If the screening detects abnormally fast blood flow (a sign of narrowed vessels), regular blood transfusions can dramatically reduce stroke risk. Even without a full stroke, smaller blockages can cause “silent strokes” that chip away at cognitive function over time, affecting memory, attention, and school performance.
Lungs and Respiratory System
Acute chest syndrome is one of the most dangerous complications of sickle cell disease and the leading cause of hospitalization. It looks and feels a lot like pneumonia: chest pain, coughing, difficulty breathing, and fever. In children, it’s usually triggered by an infection. In adults, it more often results from sickled cells blocking blood vessels in the lungs, sometimes following a pain crisis elsewhere in the body. Acute chest syndrome is a medical emergency that requires immediate hospital treatment, and repeated episodes can cause lasting lung damage that reduces your ability to breathe deeply over the years.
Kidneys
The kidneys are especially vulnerable because their internal environment, with low oxygen, high acidity, and concentrated blood flow, is exactly the kind of setting that triggers sickling. About 32% of people with sickle cell anemia show early signs of kidney damage (protein leaking into the urine) by an average age of 21. Over time, roughly 30% of adults with sickle cell anemia develop chronic kidney disease, which carries a higher mortality risk when caused by sickle cell compared to other causes of kidney disease.
The progression tends to follow a pattern. Small amounts of protein in the urine come first, often with no symptoms. Among those whose protein levels reach a certain threshold early on, 81% go on to develop persistent kidney problems. This is why regular urine testing matters: catching the damage early opens a window for treatment before kidney function declines significantly.
Bones and Joints
Blocked blood flow to bone tissue causes a condition called avascular necrosis, where bone literally dies from lack of oxygen. Up to 50% of people with sickle cell disease develop this by age 35, most commonly in the hip joint. The femoral head (the ball at the top of the thighbone) is particularly susceptible because it relies on a limited blood supply. Once the bone collapses, joint replacement may be the only option. The shoulders, knees, and ankles can also be affected, though less frequently.
Bone pain from vaso-occlusive crises, where sickled cells jam up in the small vessels inside bone marrow, is the hallmark symptom of sickle cell disease and the most common reason people end up in the emergency room.
Liver and Gallbladder
The constant destruction of red blood cells floods the body with bilirubin, a yellow waste product from broken-down hemoglobin. The liver processes this bilirubin, but the sheer volume overwhelms the system. Excess bilirubin crystallizes into black pigment gallstones. About 25% of all people with sickle cell disease develop gallstones, but the number climbs steeply with age: roughly 15% of children and 44% of adults are affected. These stones can block bile ducts, causing sudden abdominal pain, nausea, and inflammation that sometimes requires surgical removal of the gallbladder.
The liver itself can also suffer from sickled cells clogging its blood vessels, leading to episodes of liver crisis with sudden pain in the upper right abdomen, jaundice, and elevated liver enzymes.
Eyes
Sickle cells can block the tiny blood vessels in the retina, the light-sensing layer at the back of the eye. The damage progresses through stages, starting with small arterial blockages and advancing to the growth of fragile new blood vessels that can bleed into the eye or cause the retina to detach. The first three stages produce no symptoms at all, which is what makes them dangerous. By the time you notice vision changes, significant damage may already be done. Annual eye exams can catch these changes early, and laser treatment applied to areas of abnormal blood vessel growth can prevent bleeding and detachment.
Reproductive and Endocrine Systems
Up to 35% of males with sickle cell disease experience priapism: prolonged, painful erections unrelated to sexual arousal, caused by sickled cells trapping blood in the penis. Most cases are preceded by shorter “stuttering” episodes lasting under a few hours, which serve as a warning sign. Prolonged episodes that go untreated can cause permanent tissue scarring and erectile dysfunction.
Sickle cell anemia also disrupts the hormonal signals that drive puberty and growth. Children with the disease grow more slowly and move through puberty at a notably delayed pace. In one study, after two years of follow-up, 86% of control females had reached an advanced stage of puberty compared to only 36% of females with sickle cell anemia. Among males, the gap was even wider: 47% of controls had advanced, versus just 6% of those with sickle cell disease. Growth in height for boys with sickle cell anemia declined over time and was significantly slower than matched peers. The slower growth velocity is tied directly to the severity of anemia, meaning that the fewer healthy red blood cells circulating, the more growth suffers.
Heart and Circulatory System
The heart works overtime to compensate for chronic anemia. With fewer functional red blood cells carrying oxygen, the heart has to pump harder and faster to deliver enough oxygen to tissues. Over years, this extra workload enlarges the heart and can lead to heart failure, particularly of the left ventricle. Sickled cells can also damage the blood vessels in the lungs, raising pressure in the pulmonary arteries, a condition called pulmonary hypertension. This forces the right side of the heart to work harder too, creating a double burden that becomes one of the leading causes of death in adults with sickle cell disease.