Doctor's Notes on Sickle Cell Disease
Sickle cell disease is the most common hereditary blood disorder, in which, red blood cells become crescent-shaped (the sickle cell). In healthy individuals, hemoglobin (a molecule in the red blood cell) takes on oxygen and releases carbon dioxide. In sickle cell disease, the red blood cells carry an abnormal hemoglobin known as hemoglobin S which reverses normal hemoglobin activity by releasing oxygen and taking on carbon dioxide (deoxygenation). Sickle cells are very fragile and people with the disease are more likely to get infections. Sickle cell disease occurs almost exclusively among black Americans and black Africans.
Symptoms of sickle cell disease include infections (such as flu viruses, pneumonia, and salmonella). In a acute sickle cell attack (sickle cell crises) severe pain is common, and conditions or symptoms that may contribute to the painful sickle cell crisis include dehydration, infection, fever, decrease in oxygen to body tissue (hypoxia), bleeding, cold exposure, drug and alcohol use, pregnancy, and stress. Other serious symptoms of sickle cell disease include blood clots and strokes, eye problems (retinopathy, retinal detachment, bleeding in the eye), kidney damage, prolonged penis erections (priapism), spleen damage, anemia (symptoms of anemia are shortness of breath, lightheadedness, and fatigue), heart attacks, and liver problems.
Sickle Cell Disease Symptoms
The sites most often affected by the blocking or stacking action of sickled cells are found in the lungs, liver, bone, muscles, brain, spleen, penis, eyes, and kidneys.
The immune system of a person with sickled cells dramatically weakens. People with sickle cells are highly susceptible to infections from certain forms of bacteria. Some of the most common infections are from flu viruses, pneumonia, and salmonella (a type of bacteria).
Severe pain is the most common of sickle cell disease emergencies (acute sickle cell crises). A person may not know what brought on the pain, but one or more of the following situations may have contributed to the start of the painful sickle crisis:
- Hypoxia (decrease in oxygen to body tissue)
- Cold exposure
- Drug and alcohol use
- Pregnancy and stress
Four patterns of an acute sickle cell crisis are now recognizable. They are based on the part of the body where the crisis occurs.
- Bone crisis: An acute or sudden pain in a bone can occur, usually in an arm or leg. The area may be tender. Common bones involved include the large bones in the arm or leg: the humerus, tibia, and femur. The same bone may be affected repeatedly in future episodes of bone crisis.
- Acute chest syndrome: Sudden acute chest pain with coughing up of blood can occur. Low-grade fevers can be present. The person is usually short of breath. If a cough is present, it often is nonproductive. Acute chest syndrome is common in a young person with sickle cell disease. Chronic (long-term) sickle cell lung disease develops with time because the acute and subacute lung crisis leads to scarred lungs and other problems.
- Abdominal crisis: The pain associated with the abdominal crisis of sickle cell disease is constant and sudden. It becomes unrelenting. The pain may or may not be localized to any one area of the abdomen. Nausea, vomiting, and diarrhea may or may not occur.
- Joint crisis: Acute and painful joint crisis may develop without a significant traumatic history. Its focus is either in a single joint or in multiple joints. Often the connecting bony parts of the joint are painful. Range of motion is often restricted because of the pain. Avascular necrosis of the hips can occur, causing permanent damage.
Many other organ systems are often injured or impaired.
- Central nervous system: Two-thirds of all strokes in people with sickle cell disease occur in children, at an average age of 8 years. About 10% of people with sickle cell disease have strokes or other brain bleeding when younger than 8-10 years. As the population ages, the incidence of these events also increases. Repeat strokes occur in two-thirds of all survivors within 3 years of the first stroke. Blood clots affect the large vessels in the brain. Bleeding may occur in the small vessels damaged by sickle cell disease.
- Eyes: The effect of sickle cell disease on the eyes comes from the increased viscosity, or "sludging," of blood and the narrowness of the eye's blood vessels. Retinopathy (disease of the retina in the eye) is common and causes problems with vision. Retinal detachment is frequent. Hyphemas, bleeding in the eye, occur at the same rate as the general population, but complications are more common because of the increased sickling effect that the waterlike fluid in the eye promotes.
- Kidneys: Some amount of kidney damage occurs in nearly every person with sickle cell disease.
- Genitals: Priapism (a constant erection of the penis) is common. It affects about 40% of all men with sickle cell disease. Severe episodes are a frequent cause of impotency.
- Infections: People with sickle cell disease have weakened immune systems and are at increased risk for developing infection, especially in the lungs, kidneys, bones, and central nervous system.
- Repeated crises damage the spleen, which over time, causes it to stop functioning.
- Blood problems: People with sickle cell disease can develop anemia-a reduction in the number of red blood cells. Symptoms of anemia are shortness of breath (oxygen is not getting to tissues), lightheadedness, and fatigue.
- Heart attacks can occur
- The liver can also be affected by severe sickle cell crisis.
Sickle Cell Disease Causes
Sickle cell disease results from mutation, or change, of certain types of hemoglobin chains in red blood cells (the beta hemoglobin chains).
The changes in the building of normal hemoglobin result in the abnormal hemoglobin of sickle cell disease. These mutated molecules do not have the smooth motion needed for oxygenation and deoxygenation. When the oxygen concentration in the blood is reduced, the red blood cell assumes the characteristic sickle shape. This causes the red blood cell to be stiff and rigid, and stops the smooth passage of the red blood cells through the narrow blood vessels.
It does not take much imagination to see sharp-end "sickled" red cells stacking up in narrow blood vessels known as capillaries. When this happens, red blood cells are not able to carry oxygen to tissues, and tissue cell injury or death occurs. Someone with sickle cell disease would be experiencing pain with this process-the sickle cell crisis.
Anyone Can Have It
This illness means you have a lower than normal red blood cell (RBC) count. Normal values vary; blood tests like the complete blood count (CBC) can be explained by your doctor. Anemia may also result from low levels of hemoglobin, the protein that transports oxygen to the body. No matter what the cause, less oxygen is available and this produces weakness, dizziness, and shortness of breath. It is treatable once the underlying cause is identified. Long-standing or severe lack of oxygen can damage of the brain, heart, and other organs.
The three main causes of the illness are inadequate or faulty production of red blood cells, a high rate of destruction of red blood cells, and excessive bleeding. Megaloblastic is one type of faulty red cell production. The condition of anemia may be mild and easily treatable or severe and require immediate intervention.
Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.