What is Sickle Cell Disease (SCD)?
SCD is a group of inherited red blood cell disorders. Healthy red blood cells are round, and they move through small blood vessels to carry oxygen to all parts of the body. In someone who has SCD, the red blood cells become hard and sticky and look like a C-shaped farm tool called a “sickle”. The sickle cells die early, which causes a constant shortage of red blood cells. Also, when they travel through small blood vessels, they get stuck and clog the blood flow. This can cause pain and other serious problems such infection, acute chest syndrome, and stroke,” (CDC).
What Is Sickle Cell?
Figure A & B
Sickle cell anemia (uh-NEE-me-uh) is the most common form of sickle cell disease (SCD). SCD is a serious disorder in which the body makes sickle-shaped red blood cells. “Sickle-shaped” means that the red blood cells are shaped like a crescent.
Normal red blood cells are disc-shaped and look like doughnuts without holes in the center. They move easily through your blood vessels. Red blood cells contain an iron-rich protein called hemoglobin (HEE-muh-glow-bin). This protein carries oxygen from the lungs to the rest of the body.
Sickle cells contain abnormal hemoglobin called sickle hemoglobin or hemoglobin S. Sickle hemoglobin causes the cells to develop a sickle, or crescent, shape.
Sickle cells are stiff and sticky. They tend to block blood flow in the blood vessels of the limbs and organs. Blocked blood flow can cause pain, serious infections, and organ damage.
Normal Red Blood Cells and Sickle Cells
Figure A shows normal red blood cells flowing freely in a blood vessel. The inset image shows a cross-section of a normal red blood cell with normal hemoglobin. Figure B shows abnormal, sickled red blood cells blocking blood flow in a blood vessel. The inset image shows a cross-section of a sickle cell with abnormal (sickle) hemoglobin forming abnormal strands.
Overview
Sickle cell anemia is one type of anemia. Anemia is a condition in which your blood has a lower than normal number of red blood cells. This condition also can occur if your red blood cells don’t contain enough hemoglobin.
Red blood cells are made in the spongy marrow inside the large bones of the body. Bone marrow is always making new red blood cells to replace old ones. Normal red blood cells live about 120 days in the bloodstream and then die. They carry oxygen and remove carbon dioxide (a waste product) from your body.
In sickle cell anemia, the number of red blood cells is low because sickle cells don’t last very long. Sickle cells usually die after only about 10 to 20 days. The bone marrow can’t make new red blood cells fast enough to replace the dying ones.
Sickle cell anemia is an inherited, lifelong disease. People who have the disease are born with it. They inherit two genes for sickle hemoglobin—one from each parent.
People who inherit a sickle hemoglobin gene from one parent and a normal gene from the other parent have a condition called sickle cell trait.
Sickle cell trait is different than sickle cell anemia. People who have sickle cell trait don’t have the disease, but they have one of the genes that cause it. Like people who have sickle cell anemia, people who have sickle cell trait can pass the sickle hemoglobin gene on to their children.
Outlook
Sickle cell anemia has no widely available cure. However, treatments can help with the symptoms and complications of the disease. Blood and marrow stem cell transplants may offer a cure for a small number of people.
Over the past 100 years, doctors have learned a great deal about sickle cell anemia. They know its causes, how it affects the body, and how to treat many of its complications.
Sickle cell anemia varies from person to person. Some people who have the disease have chronic (long-term) pain or fatigue (tiredness). However, with proper care and treatment, many people who have the disease can have improved quality of life and reasonable health much of the time.
Due to improved treatments and care, people who have sickle cell anemia are now living into their forties or fifties, or longer.
Source: http://www.nhlbi.nih.gov/health/health-topics/topics/sca/signs
When was sickle cell disease discovered?
“This case is reported because of the unusual blood findings, no duplicate of which I have ever seen described,” James B. Herrick, M.D.
To mark the centennial of the publication of Herrick’s report, the National Institutes of Health (NIH) held the James B. Herrick Symposium–Sickle Cell Disease Care and Research: Past, Present, and Future, in November on the NIH campus in Bethesda, Md. Eight NIH Institutes and Centers sponsored the symposium, which brought together sickle cell disease experts from around the globe. (http://www.nlm.nih.gov/medlineplus/magazine/issues/winter11/articles/winter11pg21.html)
Sickle cell disease has probably been recognized for centuries in African tribal medicine. However, sickle cell disease was first recognized in Western medicine in 1910 by Dr. B. Herrick when he wrote a report about a patient who suffered from a “strange disease” that included such symptoms as pain, asthmatic conditions, and blood flow problems including body ulcers. This observation eventually led to the identification of the sickle cell hemoglobin (HbS) in the 1940s by Linus Pauling. In 1952, Pauling hypothesized on the nature of HbS and its role in sickle cell anemia by saying that the HbS proteins may act differently from regular hemoglobin (HbA) and stack together. Pauling also stated that sickling of the cells in sickle cell anemia might be due to the formation of “rods” by the hemoglobin and thus “sickle” the cell. From these hypotheses and experiments a physical understanding of sickle cell disease was formed. The physical mapping of the hemoglobin gene and protein allowed it to be one of the first human diseases to be characterized genetically. Even with these physical and genetic clues that have been known for decades, treatments (and cures) for sickle cell anemia have advanced slowly.
How common is sickle cell disease?
Sickle cell disease affects millions of people throughout the world. It is particularly common among people whose ancestors come from sub-Saharan Africa, Spanish-speaking regions (South America, Cuba, Central America), Saudi Arabia, India and Mediterranean countries, such as Turkey, Greece and Italy. In this country, it affects approximately 70,000 to 100,000 people, most with ancestors from Africa. The disease occurs in 1 in every 500 African-American births and 1 in every 1,000 to 1,400 Hispanic-American births. Approximately 2 million Americans carry the sickle cell trait.
What are the signs and symptoms of sickle cell disease?
The clinical course of sickle cell disease does not follow a single pattern. Some patients have mild symptoms, and some have very severe problems. However the basic problem is the same: the sickle-shaped red blood cells don’t live very long, causing anemia, and they tend to get stuck in narrow blood vessels, blocking the flow of blood and causing pain.
Most individuals with sickle cell disease are generally well from day-to-day. But complications of the disease can develop, often unpredictable. Some of the problems and conditions caused by sickle cell anemia include:
Fatigue, pallor (“paleness”), and decreased endurance, which are symptoms of anemia or a shortage of red blood cells.
Pain that occurs unpredictably in any body organ or joint wherever the sickled blood cells block oxygen flow to the tissues; the frequency and amount of pain varies.
Yellowing of the skin and eyes (jaundice), which results from the rapid breakdown of red blood cells.
Bacterial infections—in general, both children and adults with sickle cell anemia are more vulnerable to infections and have a harder time fighting off infection once it starts. This is a result of damage to the spleen from the sickled red cells. The spleen which normally filters the blood, when clogged with sickled cells, is prevented from destroying bacteria in the blood. Infants and young children especially are susceptible to bacterial infections that can be fatal.
The spleen can enlarge suddenly due to the entrapment of blood. This is called acute splenic sequestration, and it can cause severe and sometimes life-threatening anemia.
Acute chest syndrome is a life-threatening complication of sickle cell anemia, similar to pneumonia that is caused by infection or trapped sickled cells in the lung. This is characterized by chest pain, fever, and an abnormal chest x-ray.
Delayed growth and puberty in children and often a slight build in adults.
A stroke may occur when sickled red blood cells get trapped in the blood vessels of the brain. This causes a part of the brain to die (a stroke). This type of stroke occurs primarily in children.
Sickle cell can damage to the retina (a part of the eye), especially in older children and adult, that can be serious enough to cause blindness.
How is sickle cell disease diagnosed?
A simple blood test can determine if an individual carries at least one defective hemoglobin (S) gene. Early diagnosis of sickle cell anemia is critical so children who have the disease can receive proper treatment. Currently all 50 states have newborn screening programs. Texas initiated newborn screening in 1983, and sickle cell disease is one of the diseases that infants are screened for prior to leaving the hospital. However, most newborn screening programs are not funded to notify individuals who have sickle cell trait. If you were born in Texas prior to 1983, you should be tested for sickle cell trait. If both parents know they are carriers, they can seek genetic counseling to help them better understand sickle cell disease and how it may impact children they conceive.
How is sickle cell disease treated?
Most individuals with sickle cell disease are generally well from day-to-day. However, babies and young children with sickle cell disease should take oral penicillin twice a day, beginning as soon as sickle cell anemia is diagnosed and continuing until at least 5 years of age. This penicillin can prevent fatal pneumococcal infection. If complications of the sickle cell disease occur, patients are treated and supported until they get better. For example, painful episodes are treated with pain medications and fluids. Blood transfusions are used to treat some of the complications of sickle cell disease. Transfusions correct anemia by increasing the number of normal red blood cells in circulation.
Problems from sickle cell disease can also be prevented. For example, regular (monthly) blood transfusions can prevent strokes in children as well as prevent pain and other complications of the disease. The medicine hydroxyurea can also lower the frequency of painful episodes and of acute chest syndrome. Patients taking this drug also needed fewer blood transfusions.
Stem cell (bone marrow) transplantation can cure children with sickle cell disease. However, this procedure is not without risk, and the transplant is safest when, the bone marrow comes from a healthy sibling donor (a brother or sister with the same mother and father) with the same tissue or bone marrow type. Only about 18 percent of children with sickle cell anemia are likely to have a matched sibling donor.
The signs and symptoms of sickle cell anemia vary. Some people have mild symptoms. Others have very severe symptoms and often are hospitalized for treatment.
Sickle cell anemia is present at birth, but many infants don’t show any signs until after 4 months of age.
The most common signs and symptoms are linked to anemia and pain. Other signs and symptoms are linked to the disease’s complications.
Signs and Symptoms Related to Anemia
The most common symptom of anemia is fatigue (feeling tired or weak). Other signs and symptoms of anemia may include:
Shortness of breath
Dizziness
Headaches
Coldness in the hands and feet
Paler than normal skin or mucous membranes (the tissue that lines your nose, mouth, and other organs and body cavities)
Jaundice (a yellowish color of the skin or whites of the eyes)
Signs and Symptoms Related to Pain
Sudden pain throughout the body is a common symptom of sickle cell anemia. This pain is called a sickle cell crisis. Sickle cell crises often affect the bones, lungs, abdomen, and joints.
These crises occur when sickled red blood cells block blood flow to the limbs and organs. This can cause pain and organ damage.
The pain from sickle cell anemia can be acute or chronic, but acute pain is more common. Acute pain is sudden and can range from mild to very severe. The pain usually lasts from hours to as long as a week or more.
Many people who have sickle cell anemia also have chronic pain, especially in their bones. Chronic pain often lasts for weeks or months and can be hard to bear and mentally draining. Chronic pain may limit your daily activities.
Almost all people who have sickle cell anemia have painful crises at some point in their lives. Some have these crises less than once a year. Others may have crises once a month or more. Repeated crises can damage the bones, kidneys, lungs, eyes, heart, and liver. This type of damage happens more often in adults than in children.
Many factors can play a role in sickle cell crises. Often, more than one factor is involved and the exact cause isn’t known.
You can control some factors. For example, the risk of a sickle cell crisis increases if you’re dehydrated (your body doesn’t have enough fluids). Drinking plenty of fluids can lower the risk of a painful crisis.
You can’t control other factors, such as infections.
Painful crises are the leading cause of emergency room visits and hospital stays for people who have sickle cell anemia.
Complications of Sickle Cell Anemia
Sickle cell crises can affect many parts of the body and cause many complications.
Hand and-Foot Syndrome
Sickle cells can block the small blood vessels in the hands and feet in children (usually those younger than 4 years of age). This condition is called hand-foot syndrome. It can lead to pain, swelling, and fever.
Swelling often occurs on the back of the hands and feet and moves into the fingers and toes. One or both hands and/or feet may be affected at the same time.
Splenic Crisis
The spleen is an organ in the abdomen. Normally, it filters out abnormal red blood cells and helps fight infections. In some cases, the spleen may trap red blood cells that should be in the bloodstream. This causes the spleen to grow large and leads to anemia.
If the spleen traps too many red blood cells, you may need blood transfusions until your body can make more cells and recover.
Infections
Both children and adults who have sickle cell anemia may get infections easily and have a hard time fighting them. This is because sickle cell anemia can damage the spleen, an organ that helps fight infections.
Infants and young children who have damaged spleens are more likely to get serious infections that can kill them within hours or days. Bloodstream infections are the most common cause of death in young children who have sickle cell anemia.
Medicines and vaccines can help prevent severe illness and death. For example, vaccines are available for infections such as meningitis, influenza, and hepatitis.
Getting treatment right away for high fevers (which can be a sign of a severe infection) also helps prevent death in infants and children who have sickle cell anemia.
It’s also important to get treatment right away for a cough, problems breathing, bone pain, and headaches.
Acute Chest Syndrome
Acute chest syndrome is a life-threatening condition linked to sickle cell anemia. This syndrome is similar to pneumonia. An infection or sickle cells trapped in the lungs cause acute chest syndrome.
People who have this condition often have chest pain, shortness of breath, and fever. They also often have low oxygen levels and abnormal chest x-ray results.
Pulmonary Hypertension
Damage to the small blood vessels in the lungs makes it hard for the heart to pump blood through the lungs. This causes blood pressure in the lungs to rise.
Increased blood pressure in the lungs is called pulmonary hypertension (PH). Shortness of breath and fatigue are the main symptoms of PH.
Delayed Growth and Puberty in Children
Children who have sickle cell anemia often grow more slowly than other children. They may reach puberty later. A shortage of red blood cells causes the slow growth rate. Adults who have sickle cell anemia often are slender or smaller in size than other adults.
Stroke
Two forms of stroke can occur in people who have sickle cell anemia. One form occurs if a blood vessel in the brain is damaged and blocked. This type of stroke occurs more often in children than adults. The other form of stroke occurs if a blood vessel in the brain bursts.
Either type of stroke can cause learning problems and/or lasting brain damage, long-term disability, paralysis (an inability to move), or death.
Eye Problems
Fundus photograph of the right eye at the initial visit, showing retinal whitening in the distribution of the retinal arteriolar occlusions in the macula (A), and fundus photograph of the left eye at the initial visit, showing retinal whitening in the distribution of the retinal arteriolar occlusions in the macula, including the fovea (B). From JAMA Ophthalmology
Sickle cells also can affect the small blood vessels that deliver oxygen-rich blood to the eyes. Sickle cells can block these vessels or cause them to break open and bleed. This can damage the retinas—thin layers of tissue at the back of the eyes. The retinas take the images you see and send them to your brain.
This damage can cause serious problems, including blindness.
Priapism
Males who have sickle cell anemia may have painful, unwanted erections. This condition is called priapism (PRI-a-pizm). It happens because the sickle cells block blood flow out of an erect penis. Over time, priapism can damage the penis and lead to impotence.
Gallstones
When red blood cells die, they release their hemoglobin. The body breaks down this protein into a compound called bilirubin. Too much bilirubin in the body can cause stones to form in the gallbladder, called gallstones.
Gallstones may cause steady pain that lasts for 30 minutes or more in the upper right side of the belly, under the right shoulder, or between the shoulder blades. The pain may happen after eating fatty meals.
People who have gallstones may have nausea (feeling sick to the stomach), vomiting, fever, sweating, chills, clay-colored stools, or jaundice.
Ulcers on the Legs
Sickle cell ulcers (sores) usually begin as small, raised, crusted sores on the lower third of the leg. Leg sores may occur more often in males than in females. These sores usually develop in people who are aged 10 years or older.
The cause of sickle cell ulcers isn’t clear. The number of ulcers can vary from one to many. Some heal quickly, but others persist for years or come back after healing.
Multiple Organ Failure
Multiple organ failure is rare, but serious. It happens if you have a sickle cell crisis that causes two out of three major organs (lungs, liver, or kidneys) to fail. Often, multiple organ failure occurs during an unusually severe pain crisis.
Symptoms of this complication are fever, rapid heartbeat, problems breathing, and changes in mental status (such as sudden tiredness or confusion).
Source: www.nhlbi.nih.gov
How Is Sickle Cell Anemia Diagnosed?
A simple blood test, done at any time during a person’s lifespan, can detect whether he or she has sickle hemoglobin. However, early diagnosis is very important.
In the United States, all States mandate testing for sickle cell anemia as part of their newborn screening programs. The test uses blood from the same blood samples used for other routine newborn screening tests. The test can show whether a newborn infant has sickle hemoglobin.
Test results are sent to the doctor who ordered the test and to the baby’s primary care doctor. It’s important to give the correct contact information to the hospital. This allows the baby’s doctor to get the test results as quickly as possible.
Health providers from a newborn screening followup program may contact you directly to make sure you’re aware of the test results.
If the test shows some sickle hemoglobin, a second blood test is done to confirm the diagnosis. The second test should be done as soon as possible and within the first few months of life.
The primary care doctor may send you to a hematologist for a second blood test. A hematologist is a doctor who specializes in blood diseases and disorders. This doctor also can provide treatment for sickle cell disease if needed.
Doctors also can diagnose sickle cell disease before birth. This is done using a sample of amniotic fluid or tissue taken from the placenta. (Amniotic fluid is the fluid in the sac surrounding a growing embryo. The placenta is the organ that attaches the umbilical cord to the mother’s womb.)
Testing before birth can be done as early as 10 weeks into the pregnancy. This testing looks for the sickle hemoglobin gene, rather than the abnormal hemoglobin that the gene makes.
Epidemiology
It is estimated that sickle cell disease:-
affects 90,000 to 100,000 Americans.
occurs among about 1 out of every 500 Black or African-American births.
Worldwide it is thought to affect more than 500,000 babies a year.
How Sickle Cell Trait is Inherited
If both parents have SCT(sickle cell trait), there is a 50% (or 1 in 2) chance that any child of theirs also will have SCT, if the child inherits the sickle cell gene from one of the parents. Such children will not have symptoms of SCD, but they can pass SCT on to their children.
If both parents have SCT, there is a 25% (or 1 in 4) chance that any child of t heirs will have SCD. There is the same 25% (or 1 in 4) chance that the child will not have SCD or SCT.
If one parent has SCT, there is a 50% (or 1 in 2) chance that any child of this parent will have SCT and an equal 50% chance that the child will not have SCT.
Source: http://www.nhlbi.nih.gov/health/dci/Diseases/Sca/SCA_Diagnosis.html